Description

Technical Field

[0001] The present invention relates to the field of engines for saddle vehicles; more specifically, it refers to a phase change system for opening and/or closing at least one intake valve in an internal combustion engine for a saddle vehicle.

[0002] Further objects of the invention are a single-cylinder internal combustion engine provided with this phase change system for opening and/or closing intake valves, as well as a saddle vehicle provided with this internal combustion engine.

State of the Art

[0003] As it is well known, the timing system in an internal combustion engine is the set of components that allow to control the flows of gases into and from the combustion chambers (cylinders) by controlling the intake and exhaust valves. Generally speaking, these members work synchronously with the movement of the pistons in the cylinders; therefore, they must be perfectly "in phase" i.e. timed with the drive shaft, to which they are connected by means of kinematic members.

[0004] In the timing systems, the term "valve timing" indicates the opening and closing angles of the valves with reference to the bottom and top dead centers of the stroke of the pistons in the cylinders. In the case of intake valves, the timing affects the power delivered by the engine. For example, delaying the intake valve closing allows to increase power at high rpm, thanks to a certain degree of supercharging due to the inertial effects of air motion, but results in losses at medium and low rpm, due to charge returns in the intake ducts.

[0005] Conversely, advancing the intake valves closing improves performances at medium and low rpm.

[0006] Often, a compromise shall be made between early and late closing of the intake valves. In fact, a limited angle between valve opening and closing would reduce, especially at high rpm, the width of the phases of fresh air intake and exhaust gas discharge, thus preventing the optimal filling of the cylinders and consequently limiting the delivered power. Conversely, an excessive angle could cause the uneven operation of the engine at low rpm and a waste of unburned fuel from the exhaust valves, especially at minimum rpm.

[0007] In most recent engines, valve phasing is made variable thanks to the so-called variable valve timing (VVT) devices that improve the filling of the cylinder (by changing the timing of the valve lift) based on the rpm of the engine and, therefore, on the desired power.

[0008] A phase change system for opening and/or closing the valves in an internal combustion engine is disclosed for example in JP2012077741A. In this prior art system, two coaxial adjacent rockers, controlling two distinct valves of a cylinder and moved by respective cam lobs of the camshaft, are made integral with, or released from, each other through the mechanical action of a pin controlled by an actuator. Clearly, this prior art system for changing the timing of the valve lift is necessarily affected by both cams associated with the two rockers, even when they are coupled, thus limiting the phase change. Moreover, a phase change system with such a structure is not easily adaptable to engines requiring simple and economical VVT systems.

[0009] EP2540996B1 discloses a phase change system for opening and/or closing a valve of a cylinder of an internal combustion engine, providing for a single rocker formed by three arms hinged to a same pivot axis, i.e. an arm for controlling the valve and two arms for actuating the rocker, interacting with respective lobs of the camshaft. The system provides for a selecting pin that is moved by the oil of a hydraulic system so as to take two different positions, a position where the control arm is integral with the first actuating arm and released from the second arm, and a second position where the actuating arm is integral with the second actuating arm and released from the first one. In this way, the active arms are not affected by the cams acting on the idle arm. Clearly, the use of a hydraulic system for managing a VVT system is very complex, crucial and, lastly, expensive. Summary

[0010] The present invention aims at solving the problems associated with the phase change systems for opening and/or closing the valves of a cylinder in an internal combustion engine; more particularly, an object of the invention is to provide a phase change system for opening and/or closing an intake valve in an internal combustion engine of a saddle vehicle, which is simple from a constructive viewpoint.

[0011] A further object of the invention is to provide a phase change system for opening and/or closing an intake valve in an internal combustion engine of a saddle vehicle, which is reliable in operation.

[0012] A further object of the invention is to provide a phase change system for opening and/or closing an intake valve in an internal combustion engine of a saddle vehicle, which can be easily adapted to different types of engines.

[0013] A further important object of the invention is to provide a phase change system for opening and/or closing an intake valve in an internal combustion engine of a saddle vehicle, the rockers of which have reduced inertia.

[0014] These and other objects, that will be better described below, are achieved through a phase change system for opening and/or closing at least an intake valve in an internal combustion engine of a saddle vehicle, comprising

- a rocker pivoting around a pivot axis and adapted to transform the rotary motion of a camshaft into a motion for opening/closing at least an intake valve of the engine, and

- a selecting member adapted to interact with the rocker so that this latter takes different operative configurations to postpone or to advance the opening/closing of the intake valve, wherein the rocker comprises at least three arms, a first arm articulated around the pivot axis and provided with an area of interaction with the intake valve to allow actuating the valve, and at least a second and a third arm, both articulated around the pivot axis and provided with respective areas of interaction with the camshaft to allow the rocker to move based on the rotation of the camshaft, and wherein the at least three arms respectively define at least a first, a second and a third portion of a sliding channel for the selecting member, so that the selecting member is adapted to slide in this sliding channel so as to take at least two positions, a position adapted to make the first arm and the second arm rotate integrally around the pivot axis, and a position adapted to make the first arm and the third arm rotate integrally around the pivot axis, so that, based on the position taken by the selecting member in the sliding channel, the rocker takes different operative configurations for opening/closing the intake valve; the peculiarity of this system is that the selecting member comprises at least two axially adjacent pins sliding in the channel and provided with two respective operative ends that always touch each other, respectively at least an engagement pin for engaging the channel portions and at least an extension pin in contact with a pushing body that is at least partially external to the channel; the pushing body is adapted to push the engagement pin by thrusting the extension pin, and wherein the extension pin is adapted to slide in only one channel portion.

[0015] This particular configuration of the rocker and the selecting member allows to provide a phase change system for opening and/or closing the intake valve that is completely mechanical and, at the same time, has independent phase configurations for opening and/or closing the valve, i.e. each phase configuration is associated with only one cam of the camshaft.

[0016] Each arm preferably has a respective hole for the insertion of a common pivot shaft.

[0017] The engagement pin is preferably a single pin, i.e. formed by a single piece; in further embodiments it is formed by several portions that are axially separate but have such an axial length to engage two channel portions at a time.

[0018] Similarly, the extension pin is a single pin, i.e. formed by a single piece; in further embodiments it is formed by several portions that are axially separate but have such an axial length to serve as an extension.

[0019] The engagement pin preferably has round cross section; in further embodiments it has a different shape, for example polygonal or elliptical or irregular shape. [0020] The extension pin preferably has round cross section; in further embodiments it has a different shape, for example polygonal or elliptical or irregular shape.

[0021] Preferably, both the extension pin and the engagement pin have round crosssections, but they can have differently shaped cross-sections; for instance, one pin has round cross section and the other one has polygonal cross section.

[0022] The cross-sections of the channel portions are preferably round, but they can be shaped complementary to the shape of the pins sliding inside them.

[0023] According to preferred embodiments, the second and the third arm are provided at opposite sides of the first arm, i.e. the first arm is provided between the second and the third arm.

[0024] According to preferred embodiments, the engagement pin is adapted to engage two channel portions, in particular it is adapted to engage always the first channel portion and, alternatively, the second channel portion or the third channel portion, and the extension pin is adapted to engage only the second channel portion.

[0025] According to preferred embodiments, the pushing body is adapted to push the extension pin so as to move it from

- a first position, wherein the extension pin is spaced from the first arm and the engagement pin (touching the extension pin) contemporaneously engages the first channel portion and the second channel portion, so that the first arm and the second arm rotate integrally, to

- a second position, wherein the extension pin is closer to the first arm with respect to the first position and the engagement pin is outside the second channel portion and contemporaneously engages the first channel portion and the third channel portion, so that the first arm and the second arm rotate integrally.

[0026] According to preferred embodiments, the extension pin has a part projecting outside the second channel portion; this projecting part is adapted to be in contact with the pushing body. [0027] According to preferred embodiments, the engagement pin and the extension pin have different transverse width; preferably the engagement pin has at least a cross section larger than that of the extension pin; preferably the second channel portion has a change in cross section defining an end of stroke abutment for the engagement pin.

[0028] According to preferred embodiments, a pushing device is provided in the third channel portion for pushing the engagement pin towards the second channel portion when the engagement pin engages the third channel portion; the pushing device preferably comprises an elastic element acting by compression.

[0029] According to preferred embodiments, the pushing body is substantially not- aligned with, i.e. parallel to, the extension pin along a same movement direction, or the pushing body is substantially aligned with the extension pin along a same movement direction.

[0030] According to preferred embodiments, the system comprises an actuator for moving the pushing body; the actuator preferably has an actuating head movable parallel to the pushing body or coaxially with the extension axis of the pushing body; the actuator is preferably an electro-mechanical solenoid actuator.

[0031] According to preferred embodiments, the system comprises at least a hindering device preventing the second arm and the third arm from moving away from the respective cams of the camshaft; the hindering device is preferably a yielding device adapted to keep the arms touching the respective cams; the hindering device is preferably a torsion spring fastened to the first, the second and the third arms.

[0032] According to preferred embodiments, the system comprises only three arms, each of which defines a respective channel portion; preferably, only one engagement pin and only one extension pin being provided.

[0033] According to a further aspect, the invention also refers to a single-cylinder internal combustion engine for a saddle vehicle, comprising a cylinder, a piston sliding in the cylinder, a drive shaft kinematically connected to the drive shaft, a timing system comprising at least an intake valve for gas intake in the cylinder, at least an exhaust valve for gas discharge from the cylinder, and a camshaft; the engine is characterized by comprising a phase change system for opening and/or closing the intake valve according to one or more of the embodiments described above.

[0034] According to a further aspect, the invention also relates to a saddle vehicle comprising this single-cylinder internal combustion engine.

Brief description of the drawing

[0035] The invention shall be better understood by following the description and the accompanying drawing, which show non-limiting examples of embodiment of the invention. More particularly, in the drawing:

Fig. 1 is a schematic view of a saddle vehicle with the phase change system of the invention;

Fig. 2 is a cut-away schematic view of a portion of engine of a saddle vehicle with the phase change system of the invention;

Fig. 3 is an axonometric schematic view of a portion of engine with a phase change system according to the invention;

Fig. 4 is a schematic axonometric view of a phase change system according to the invention in the engine shown in the previous figures;

Fig. 5 is a schematic side view of the system of Fig. 4;

Fig. 6 is a schematic cross section of the system of Fig. 4, in a first operative configuration;

Fig. 7 is a schematic cross section of the system of Fig. 4, in a second operative configuration;

Fig. 8 is an exploded axonometric view of a rocker of a phase change system according to the invention.

Detailed description of embodiments [0036] With reference to the previously cited figures, a saddle vehicle is indicated as a whole with the reference number 1000. In Fig. 2, only a portion of the vehicle is shown, referring to the engine 100.

[0037] The engine 100 is an internal combustion engine that will be described only briefly below, except as regards a phase change system 10 for opening and/or closing the intake valves of the engine.

[0038] The engine 100 is schematically shown in Fig. 2. In particular, it comprises a base 101 where a cylinder 102 is provided, inside which a piston 103 slides. The head 101A is fastened to the base 101, at the top. A timing system is associated with the cylinder 102, the system comprising a gas intake valve 104 allowing the opening and closing of two intake ports 105 on the cylinder, a gas exhaust valve 106 allowing the opening and closing of two exhaust ports 107 on the cylinder, a camshaft 108 interacting with the intake and exhaust valves through respective rockers.

[0039] In particular, a rocker 11 is associated with the intake valve 104 and forms part of the phase change system 10 for opening and/or closing the intake valve 104.

[0040] The rocker 11 pivots on a pivot shaft 12 having a pivot axis X, and transforms the rotary motion of the camshaft 108 into an opening/closing movement of the intake valve 104.

[0041] In more detail, the rocker 11 comprises three arms. A first arm 13 has a first hole 14, for the insertion of the pivot shaft 12 to allow the pivot shaft to rotate around the pivot axis X, and is provided with an area of interaction with the intake valve 104 to allow the control thereof. In particular, the first arm 13 has an initial segment 13 A, which divides into two end segments 13B interacting with respective plates 15 (associated with return springs, not shown in the figures) closing the respective intake ports 105.

[0042] The rocker 11 has a second arm 16 and a third arm 17, both provided with respective holes 18 and 19 for the insertion of the same pivot shaft 12 to allow the pivot shaft to rotate around the pivot axis X. [0043] In particular, the second arm 16 and the third arm 17 are provided, along the axis X, at opposite sides of the first arm 13, so that the first arm is arranged between the second arm and the third arm.

[0044] The second arm 16 and the third arm 17 have respective areas of interaction with respective cams of the camshaft 108. These areas are embodied by a first and a second rotating brush 20 and 21 touching the respective cams, according to known construction methods. The areas of interaction with the camshaft are provided approximately at the opposite side of the pivot axis X relative to the areas of interaction with the intake valves, so that the rocker is a first-class lever.

[0045] As it will be described in greater detail below, from an operative viewpoint, a selecting member 22, controlled in actuation for example based on the rpm, allows to make either the first arm 13 and the second arm 16, or the first arm 13 and the third arm 17, rotate integrally around the pivot axis, so that, based on the combination, the rocker takes two different operative configurations for opening/closing the intake valve, for postponing or advancing the opening/closing thereof.

[0046] In more detail, the first arm 13, the second arm 16 and the third arm 17 respectively define a first, a second and a third portion of a sliding channel 23, 24 and 25 for the selecting member 22. According to the arrangement of the arms, the second and the third channel portion 24 and 25 are provided along the axis X at opposite sides of the first channel portion 23, so that the first channel portion 23 is arranged between the second and the third channel portion.

[0047] The selecting member 22 e adapted to slide in the sliding channel 23-24-25 to take two positions, a position adapted to make the first arm 13 and the second arm 16 rotate integrally around the pivot axis X (as shown in Fig. 6), and a position adapted to make the first arm 13 and the third arm 17 rotate integrally around the pivot axis X (as shown in Fig. 7), so that, based on the position taken by the selecting member in the sliding channel, the rocker takes different operative configurations for opening/closing the intake valve.

[0048] The selecting member 22 comprises two axially adjacent pins sliding in the sliding channel 23-24-25, i.e. an engagement pin 26 and an extension pin 27, having two respective operative ends 26A and 27A always touching each other. [0049] Each pin 26 and 27 is preferably made in a single piece and has round cross section, the cross section of the engagement pin 26 having larger diameter than the cross section of the extension pin 27.

[0050] The engagement pin 26 is adapted to engage two channel portions, in particular it is adapted to engage always the first channel portion 23 and, alternatively, the second channel portion 24 or the third channel portion 25. Conversely, the extension pin 27 is adapted to engage, and to slide in, only the second channel portion 24 (i.e. it does not engage the first and the second channel portion), a part 27B of the extension pin projecting outside the sliding channel 23-24-25.

[0051] A pushing body 28 is provided outside the sliding channel 23-24-25, for pushing the engagement pin 26 by pushing the extension pin 27 (extension pin and engagement pin are axially in contact with each other) at the projecting part 27B.

[0052] In more detail, the pushing body 28 is adapted to push the extension pin 27 for moving it between two positions:

[0053] a first position, wherein the extension pin 27 is spaced from the first arm 13 and the engagement pin 26, touching the extension pin, contemporaneously engages the first channel portion 23 and the second channel portion 24, so that the first arm 13 and the second arm 16 rotate integrally when rotate around the pivot axis X;

[0054] a second position, wherein the extension pin 27 is closer to the first arm 13 with respect to the first position, and the engagement pin 26 is outside the second channel portion 24 and contemporaneously engages the first channel portion 23 and the third channel portion 25, so that the first arm and the second arm rotate integrally when rotate around the pivot axis X.

[0055] The first channel portion 23 and the third channel portion 25 have round cross sections that are essentially complementary to the cross section of the engagement pin 26.

[0056] The second channel portion 24 has two parts, whose cross section have different diameter, a first part 24 A of larger diameter, having diameter equal to that of the first channel portion 23, and a second part 24B of smaller diameter, substantially complementary to the cross section of the extension pin 27. [0057] Therefore, the second channel portion 24 has a change in cross section defining an end of stroke abutment 24C for the end 26 A of the engagement pin 26.

[0058] In the third channel portion 25 a pushing device 29 is provided for pushing the end 26B (opposite to the end 26A) of the engagement pin 26 towards the second channel portion 24 when the engagement pin engages the third channel portion 25. In this example, the pushing device 29 comprises an elastic element 29A (with which a glass-shaped element 29B is associated, where the engagement pin abuts, provided at the operative end thereof), adapted to be compressed by the engagement pin when the engagement pin moves from the first channel portion 23 toward the third channel portion 25.

[0059] The pushing body 28 is, for example, a rod that can slide parallel to the pivot axis X, for instance inside a suitable guide 30, for example fixed relative to the head or the base of the engine.

[0060] The system 10 further comprises an actuator 31 for moving the pushing body 28. The actuator, for example a solenoid electro-mechanical actuator, has an actuating head 31 A movable parallel to the extension axis of the pushing body 28 (or, in further embodiments, coaxially with the extension axis).

[0061] A first end 28A of the pushing body 28 touches the end 27B of the extension pin 27 opposite to the end 27A of contact with the engagement pin 26. A second end 28B of the pushing body, opposite to the first end 28A, touches the actuating head 31A.

[0062] Adequately, the system comprises a hindering device 32 preventing the second arm 16 and the third arm 17 from moving away from the respective cams of the drive shaft, i.e. preventing from rotating around the axis X. The hindering device 32 is for example a yielding device adapted to keep the arms 16 and 17 touching the respective cams; in this embodiment, the hindering device is a torsion spring 32 fastened to the second and the third arms 16 and 17 and abutting against the first arm 13. Therefore, the second and the third arm 16 and 17, with the respective first and second rotating brushes 20 and 21, touch respective cams. Both the cams have a common arc of rotation of constant radius, i.e. they do not contribute to the movement of the second and the third arm of the rocker. During the arc of rotation, thanks to the torsion spring 32, the second and the third arm are synchronized, i.e. they have the same angular position relative to the axis X, whilst they have different angular position when they slide on the cams.

[0063] The operation of the system is as follows.

[0064] The selecting member formed by the pins 26-27 is in the first operative position described above, i.e. With the engagement pin inserted in the first channel portion 23 and in the second channel portion 24, and the extension pin 27 partially outside the second channel portion 27, so that the second arm and the first arm are integral in rotation, forming a first operative configuration of the rocker (Fig. 6). This first operative configuration of the rocker occurs at low rpm, when the second arm 16 touches a cam allowing to advance the opening of the intake valve, thus optimizing the performance of the engine.

[0065] When the rpm increases, a control is sent to the actuator 31, which moves so as to push, with the head 31 A, the pushing body 28 toward the second arm 16. The pushing body pushes the extension pin 27, which forces the engagement pin to exit the second channel portion 24 and to enter the third channel portion 25, against the action of the pushing device 29, so that the selecting member achieves the second operative position, and the first arm 13 is integral in rotation with the third arm 17, forming a second operative configuration of the rocker (Fig. 7). In this configuration, the third arm 17 touches a cam delaying the opening of the intake valve, thus improving the performance of the engine.

[0066] By decreasing the rpm again, the actuator 31 controls the head 31 A to move backward, so that the force of the pushing device 29 brings the gear train formed by engagement pin- extension pin - pushing body toward the actuator, i.e. in the first operative position described above (in fact, the engagement pin 26 exits the third channel portion 25 and enters the second channel portion 24, so that the second arm and the first arm are integral in rotation).

[0067] It is understood that what is illustrated purely represents possible non-limiting embodiments of the invention, which may vary in forms and arrangements without departing from the scope of the concept on which the invention is based. Any reference numerals in the appended claims are provided for the sole purpose of facilitating the reading thereof in the light of the description above and the accompanying drawings and do not in any way limit the scope of protection.