Patent Description:
Internal combustion engines rely on critical timing of air/fuel injection and exhaust of gases with the stroke of pistons. The control of valves and fuel pumps is often achieved by camshafts that rotate in a synchronized manner with a crankshaft via a belt or chain. The crankshaft rotation is caused by the piston motions.

A camshaft comprises of a shaft and at least one, often several, cams arranged on the shaft. As the shaft rotates, the cam moves around the rotation axis of the shaft and causes a force on a control element to for example open or close a valve depending on the rotational position of the camshaft or cause a fuel pump to inject fuel.

A camshaft is supported by a bearing in order to allow for it to rotate with little resistance. Generally, such bearings should preferably not be exposed to radial forces, transversal to the camshaft main axis in order to ensure satisfactory lifetime for the bearings.

The present disclosure generally relates to a vehicle engine with a force transfer arrangement for transferring a force from a rotating camshaft to an output device, that can reduce the transversal force on the camshaft, to thereby improve the lifetime of the cam shaft and bearing, but also reduce vibrations caused transversal forces on the camshaft.

The proposed force transfer arrangement is configured to cause forces to act on the camshaft from substantially opposite directions which effectively produces a resultant force on the camshaft to be close to zero, or at least be reduced compared to prior art force transfer solutions. Thus, the transverse forces on the camshaft and therefore on e.g. bearings supporting the camshaft are reduced whereby the lifetime of the bearings is prolonged and issues related to noise, vibrations, and harshness can be alleviated.

The above advantages are provided by allowing two force transfer elements to be in contact with the camshaft when transferring force to the same output element in such a way that, when the force transfer elements transfers force to the output element, they are at the same time causing resulting forces that are directed substantially towards each other. In other words, the main part of the force caused on the camshaft by the first force transfer element is in opposite direction to the main part of the force caused on the camshaft by the second force transfer element.

More precisely, the inventors propose a force transfer arrangement for transferring a force from a rotating camshaft to an output device. The force transfer arrangement comprises a first transfer element being in contact with the camshaft and configured to transfer force from the camshaft to the output device when the camshaft rotates. Further, a second transfer element being in contact with the camshaft and configured to transfer force from the camshaft to the output device when the camshaft rotates. The forces on the camshaft caused by the first transfer element and the second transfer element when transferring forces to the output element, are in substantially opposite directions.

Further features of, and advantages with, the embodiments of the present disclosure will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present disclosure may be combined to create embodiments other than those described in the following, without departing from the scope of the present disclosure.

These and other aspects of the present disclosure will now be described in more detail, with reference to the appended drawings showing example embodiments of the present disclosure, wherein:.

In the present detailed description, various embodiments of a force transfer arrangement according to the present disclosure are described. However, embodiments of the present disclosure may be realized in many different forms and should not be construed as limited to the embodiments set forth herein; rather, these embodiments are provided for thoroughness and completeness, and to fully convey the scope of the invention to the skilled person.

<FIG> conceptually illustrates an exemplary combustion engine <NUM> for a vehicle. The combustion engine comprises multiple cylinders (not shown) and multiple pistons <NUM>. In each of the cylinders is a respective piston <NUM> arranged. The pistons <NUM> are forced to move in the respective cylinder by the ignition of fuel in the cylinder volume. The stroke motion of the piston in the cylinder is transferred to a crankshaft <NUM> for transferring propulsion power to the driveline (not shown) of the vehicle comprising the combustion engine <NUM>.

Further, in order to allow air to mix with the fuel in the cylinder volume a valve <NUM> (only one of several valves is numbered) is configured to open an air inlet to the cylinder volume at timed intervals. The timing is provided by a linking mechanism <NUM> (a so-called "timing belt") which is configured to rotate a first camshaft <NUM> about a rotation axis <NUM> such that a cam <NUM> of the camshaft <NUM> causes the first valve <NUM> to open and close in a synchronized manner with respect to the rotation of the crankshaft and thereby with respect to the strokes of the piston <NUM>.

Furthermore, a second camshaft <NUM> is configured to open and close a second valve <NUM> (only one is numbered). The timing of the operation of the second valve <NUM> is also is provided by the linking mechanism <NUM>. Thus, the linking mechanism is configured to rotate the second camshaft <NUM> about a rotation axis <NUM> such that a cam <NUM> of the second camshaft <NUM> causes the second valve <NUM> to open and close in a synchronized manner with respect to the rotation of the crankshaft <NUM> and thereby with respect to the strokes of the piston <NUM>.

The second valve <NUM> may control the outflow of exhaust from the cylinder volume in a synchronized manner with the rotation of the crankshaft <NUM> and thereby with respect to the strokes of the piston <NUM>.

The configuration of the engine <NUM> shown in <FIG> is purely exemplary and should not be construed as limiting the scope of the appended claims. For example, the camshaft may be arranged to additionally control fuel pumps or oil pumps, or other example output devices.

<FIG> conceptually illustrates a partial camshaft <NUM> with a conceptual cam <NUM>. The cam <NUM> is in contact with a push element <NUM> adapted to be pushed towards the spring <NUM> as the camshaft <NUM> rotates and the wider portion of the cam <NUM> aligns with the push element <NUM>. When the narrower portion of the cam <NUM> aligns with the push element <NUM>, the spring <NUM> expands and pushes the push element <NUM> in the direction towards the camshaft <NUM> such that the push element <NUM> maintains contact with the cam <NUM>. The push element <NUM> is arranged to control an output device <NUM> adapted to control e.g. a fuel pump or an oil pump. For example, when the push element <NUM> is pushed away from the camshaft <NUM> and thereby compresses the spring <NUM>, the fuel pump may be caused to inject fuel into the engine of the vehicle.

<FIG> illustrates an example prior art arrangement. Here, the camshaft <NUM> includes the cam <NUM> which has a wide dimension <NUM> and a narrow dimension <NUM>. A coupling element <NUM> is here arranged to control a conceptually illustrated fuel pump <NUM>. A spring <NUM> ensures that the coupling element <NUM> is in contact with the camshaft <NUM>. Thus, when the camshaft rotates and moves the coupling element <NUM> by means of the cam profile, the coupling element <NUM> causes the spring <NUM> to compress at the same time as the fuel pump <NUM> is controlled by the motion. When the camshaft <NUM> causes the output device <NUM> to compress the spring <NUM>, a counter force <NUM> acts on the camshaft and therefore also on bearings supporting the camshaft <NUM>. This force <NUM> acts transversal to the axis of the camshaft and causes tear on the bearings and the support structures for the camshaft <NUM>. The embodiments of the present disclosure alleviate this problem.

<FIG> conceptually illustrates an embodiment of a force transfer arrangement according to embodiments of the present disclosure. Accordingly, <FIG> conceptually illustrates a force transfer arrangement <NUM> for transferring a force from a rotating camshaft <NUM> to an output device <NUM>. The force transfer arrangement <NUM> comprises a first transfer element <NUM> being in contact with the camshaft <NUM> and configured to transfer force from the camshaft <NUM> to the output device <NUM> when the camshaft rotates. A second transfer element <NUM> is in contact with the camshaft <NUM> and is configured to transfer force from the camshaft <NUM> to the output device <NUM> when the camshaft <NUM> rotates. The forces on the camshaft <NUM> caused by the first transfer element <NUM> and the second transfer element <NUM> when transferring forces to the output element, are in substantially opposite directions.

<FIG> illustrates the camshaft <NUM> in a rotational orientation where the cam <NUM> has its narrow dimension <NUM> substantially aligned with the force transfer elements <NUM> and <NUM> such that they cause little or no translational action on the output device <NUM>, in other words, the output device is in a first position which may be a withdrawn position.

<FIG> illustrates the force transfer arrangement <NUM> when the camshaft <NUM> has rotated such that the wide portion <NUM> of the cam <NUM> causes the force transfer element <NUM> to be pushed away in a first direction from a rotation axis of the camshaft <NUM> to transfer force to the output device <NUM>. Further, with the camshaft <NUM> in this orientation, the second force transfer element <NUM> is arranged to be pushed away in a second direction from the rotation axis of the camshaft when transferring force to the output device <NUM>. The first direction is substantially opposite to the second direction. Preferably, the first transfer element <NUM> may be arranged to be pushed away in the first direction by the camshaft <NUM> at the same time as that the second transfer element is pushed away in the second direction.

The force <NUM> caused by the first transfer element <NUM> on the camshaft <NUM> that is opposite to the force <NUM> caused by the second force transfer element <NUM> are of substantially equal magnitude, and preferably the main parts of the forces are in opposite directions. Consequently, the resultant force on the camshaft is substantially zero.

Accordingly, the inventors realized that by arranging two force transfer elements to act simultaneously on the camshaft to transfer force to the same output device, in such a way that they at least partly act in opposite directions on the camshaft, the resultant force on the camshaft may be at least reduced. Thereby, the wear on the camshaft and the bearings supporting the camshaft may be reduced and their lifetime prolonged. Further, potential NVH (Noise, Vibration, Harshness) issues related to lash in the camshaft bearing is reduced to a minimum by means of embodiment of the present disclosure.

That the forces acting on the camshaft are in substantially opposite directions should be broadly interpreted to include that at least a component of the forces act in opposite directions. Preferably, the main parts/components of the forces act in opposite directions such that the resultant force is kept as small as possible. However, a deviation from opposite is allowed, as is exemplified in <FIG>. The same interpretation applies to the that the force transfer elements may be arranged to be pushed away in substantially opposite directions, i.e. a deviation from opposite directions is allowed as long as the resultant force on the camshaft is kept small.

The general inventive concept of the present disclosure may be implemented in various way, with the aim to reduce the transversal force on the camshaft by configuring first transfer element and the second transfer element such that when transferring forces to the output element, the forces on the camshaft are in substantially opposite directions. One such possible implementation will now be described in more detail with reference to <FIG>.

Turning to <FIG>, the first transfer element <NUM> is rotationally attached adjacent to the camshaft and is rotatable about a rotation axis <NUM>, wherein the first transfer element includes a contact portion <NUM> being in contact with the camshaft <NUM>, and a transfer portion <NUM>, wherein when the contact portion <NUM> is pushed away from a rotation axis <NUM> of the camshaft <NUM>, the transfer portion <NUM> is arranged to move in a substantially opposite direction to thereby transfer force to the output device <NUM>. In other words, the first force transfer element <NUM> is rotated about its rotation axis <NUM> by the force applied to it by the camshaft <NUM>. The rotation causes the transfer portion to travel along the circumference of the rotational motion, and to thereby transfer force towards the output device <NUM>. Thereby, one possible way to enable a force to be transferred from one side of the camshaft <NUM> main axis to the other side, where the output device <NUM> is located, is provided.

The first transfer element <NUM> includes the contact portion <NUM> arranged to receive the force from the cam <NUM> of the camshaft. Further, the first force transfer element has an extension, the transfer portion <NUM>, that reaches past the camshaft width so that it may transfer force to the other side of the camshaft <NUM> main axis. In <FIG>, the transfer portion <NUM> reaches above the camshaft <NUM>. For this, the length of the first transfer element <NUM>, from the contact portion <NUM> to the transfer portion <NUM> exceeds the width of the camshaft preferably that width of the wide portion <NUM> of the cam <NUM>.

The contact portion <NUM> may be configured as a here conceptually illustrated rolling element <NUM> that is supported by a conceptually illustrated bearing <NUM> such that the rolling element rotates as it moves along the periphery of the cam <NUM>.

The transfer portion <NUM> is arranged to push on a linkage arm <NUM> when the first transfer element <NUM> rotates, to thereby transfer force from one side of the camshaft to the output device <NUM>. The linkage arm may be arranged in a guiding passage <NUM> of the engine. The coupling between the linkage arm <NUM> and transfer element <NUM> does not require the linkage arm <NUM> and the transfer element <NUM> be mechanically attached to each other. The linkage arm may have a substantially planar surface that is in contact with the transfer element <NUM> by the forces present in the arrangement <NUM>. For example, the forces transferred from the camshaft <NUM> and counterforces from the output device <NUM> may ensure that the linkage arm <NUM> and the transfer element <NUM> maintain contact. At the contact interface between the linkage arm <NUM> and the transfer element <NUM>, the transfer element <NUM> may include a convex portion to account for the rotational motion of the transfer element <NUM> and reduce wear in the contact interface.

It may also be possible to have the linkage arm <NUM> be pivotally attached to the transfer element <NUM>.

The second force transfer element <NUM> is arranged to be linearly displaced when the camshaft <NUM> rotates, to transfer force to the output element <NUM>. Thus, as the second force transfer element <NUM> alternatively contacts the narrow part and the wide part of the cam <NUM>, the second force transfer element <NUM> is displaced linearly in a direction away from or towards the camshaft axis <NUM>. The second force transfer element <NUM> may be arranged to be linearly displaced towards the output device <NUM>. In this way may an efficient transfer of force to the output device <NUM> be obtained.

Similar to the contact portion <NUM> of the first transfer element, the second transfer element <NUM> may include a rolling element <NUM> that is rotatable about a center axis <NUM> by means of a bearing. Thus, when the camshaft rotates the rolling element <NUM> rotates to thereby travel along the periphery of the cam <NUM>.

The first transfer element <NUM> may be mechanically coupled to the second force transfer element <NUM>. Here, in <FIG>, the transfer portion <NUM> of the first transfer element <NUM> is coupled to a coupling portion <NUM> of the second force transfer element <NUM>. Accordingly, when the contact portion <NUM> of the first transfer element <NUM> is pushed away from the camshaft axis <NUM> by the cam <NUM>, the transfer portion <NUM> rotates towards the side of the camshaft where the second force transfer element <NUM> is located. The linkage arm <NUM> is consequently caused to push on the coupling portion <NUM>. At the same time, the cam <NUM> causes the second transfer portion <NUM> to be pushed away from the camshaft axis <NUM> in a direction which is substantially opposite to the direction of the motion of the first force transfer element contact portion <NUM>, and in a direction substantially parallel with the direction of the motion of the linkage arm <NUM> as it is pushed by the transfer portion <NUM>. In this way, are the forces transferred by the force transfer elements synchronized. Further, in this way, the first transfer element <NUM> and the second transfer element <NUM> are arranged such that the forces transferred by the first transfer element <NUM> and the second transfer element <NUM> to the output device <NUM> are added to each other.

The linkage arm <NUM> may be pivotally attached to the coupling portion <NUM>, or as conceptually illustrated in <FIG>, the linkage arm <NUM> may be placed in a cavity or hole <NUM> of the coupling portion where it is guided and maintain in place such that it can push on the coupling portion <NUM>. With the linkage arm <NUM> placed in a cavity or hole <NUM>, the linkage arm <NUM> does not have to be mechanically attached to the coupling portion <NUM>.

The second transfer element <NUM> including the coupling portion <NUM> and the rolling element <NUM> are held in place by the counter-force from the output device <NUM>, here the counter-force is provided by the spring <NUM>. Accordingly, on one side of the second transfer element <NUM> the spring <NUM> applies a force, and on the opposite side of the second transfer element <NUM> is the linkage arm <NUM> and the cam <NUM> arranged in contact with the second transfer element <NUM> to counter-act the spring force. The spring <NUM> thus pushes the second transfer element <NUM> towards the linkage arm <NUM> and the cam <NUM> such that the second transfer element <NUM> in held in place therebetween. The spring <NUM> maintains a pressure on the second transfer element <NUM> such that it is pushed towards and maintain contact with the cam <NUM> of the camshaft <NUM>. The second transfer element <NUM> is thus suspended by the force applied by the spring <NUM> that causes the second transfer element to be pressed against the linkage arm <NUM> and the camshaft <NUM>.

Further, the linkage arm <NUM> has a rounded front end <NUM> that fits in the hole <NUM>, or in some cases trench. The hole <NUM> or trench is somewhat larger in diameter than the diameter of the linkage arm <NUM> such that the linkage arm <NUM> is adapted to pivot in the hole <NUM> as the second force transfer element <NUM> is in motion. The ensures a smooth motion of the second transfer element when the linkage arm <NUM> applies its force on the second transfer element <NUM> at the same time as the cam <NUM> applies its force on the second transfer element <NUM>.

The second transfer element <NUM> is preferably coupled to the output device <NUM> by that the output device <NUM> pushes on a surface of the second transfer element <NUM> without the second transfer element and the output device being mechanically attached to each other.

The linkage arm <NUM> applies its force on the second transfer element <NUM> a distance away from where the cam <NUM> applies its force on the the rolling element <NUM>. Accordingly, the hole <NUM> is spaced apart from the the rolling element <NUM>. Furthermore, the output element <NUM> is arranged in contact with the second force transfer element <NUM> at a location between the hole <NUM> and the rolling element <NUM>, but on the opposite side of the second force transfer element <NUM> with respect to the linkage arm <NUM> and the hole <NUM>.

Preferably, and as illustrated in <FIG>, the first transfer element <NUM> and the second transfer element <NUM> are arranged to be pushed by the same cam <NUM> on the camshaft <NUM>. The cam <NUM> has lobes <NUM>, <NUM> on opposite sides of the camshaft <NUM>.

Preferably, the first transfer element <NUM> and the second transfer element <NUM> may be arranged to be pushed by cams having profiles that matches the positions of the respective one of the first transfer element <NUM> and the second transfer element <NUM>. In other words, the relative position of the lobes <NUM>, <NUM> with respect to each other, matches the relative positions of the rolling element <NUM> of the second force transfer element and the rolling element <NUM> of the first force transfer element. Thus, when one of the lobes <NUM>, <NUM>, is in contact with one of the rolling elements <NUM>, <NUM>, then the other one of the lobes <NUM>, <NUM>, is in contact at the widest part with width <NUM> with the other one of the rolling elements <NUM>, <NUM>.

The force transfer arrangement <NUM> is accommodated in a housing which is attached to the engine at the attachment holes <NUM>. The housing defines a space <NUM> between the housing and the engine. The spacing between the housing and the engine is limited to prevent e.g. the second force transfer element to move sideways, i.e. in or out of the plane of the drawing in <FIG>.

The output device <NUM> may be configured in various ways. Here, a spring <NUM> is arranged to provide a counter force to the first transfer element <NUM> and the second transfer element <NUM> such that the first transfer element and the second transfer element maintain contact with the camshaft <NUM>. The spring provides a spring-loaded control of the e.g. fuel pump. The spring may for example be arranged in contact with a stop element <NUM> attached to or coupled with a shaft <NUM> connected to the coupling portion <NUM> of the second transfer element <NUM>. The shaft <NUM> transfers forces from the first and second transfer element to the fuel pump and is arranged coaxially, inside the spring <NUM>. The shaft <NUM> is arranged in a though-hole of the stop element <NUM> which may be provided in the form of a washer. The outer diameter of the washer is larger than the diameter of the spring <NUM> such that the spring can be pushed by the washer and is prevented from falling out of a guiding passage <NUM> leading to the fuel pump.

The output device <NUM> may be adapted to control a fuel pump or an oil pump. Embodiments of the present disclosure are advantageous for such devices since they tend to cause relatively high loads on the camshaft, as compared to for example valves which often cause less load.

Claim 1:
A vehicle engine comprising a camshaft, an output device, and a force transfer arrangement (<NUM>) for transferring a force from the rotating camshaft (<NUM>) to the output device (<NUM>), the force transfer arrangement comprising:
a first transfer element (<NUM>) being in contact with the camshaft and configured to transfer force from the camshaft to the output device when the camshaft rotates, wherein the first transfer element is rotationally attached adjacent to the camshaft and is rotatable about a rotation axis (<NUM>), wherein the first transfer element includes a contact portion (<NUM>) being in contact with the camshaft, and a transfer portion (<NUM>), wherein when the contact portion is pushed away from a rotation axis (<NUM>) of the camshaft, the transfer portion is arranged to move in a substantially opposite direction to thereby transfer force to the output device, wherein the first transfer portion is arranged to push on a linkage arm (<NUM>) when the first transfer element rotates, to thereby transfer force from one side of the camshaft to the output device;
a second transfer element (<NUM>) being in contact with the camshaft and configured to transfer force from the camshaft to the output device when the camshaft rotates, wherein the second force transfer element is arranged to be linearly displaced when the camshaft rotates, to transfer force to the output element;
wherein the first transfer element and the second transfer element are arranged to be pushed by lobes (<NUM>, <NUM>) arranged on opposite sides of the camshaft;
wherein the forces on the camshaft caused by the first transfer element and the second transfer element when transferring forces to the output element, are in substantially opposite directions.