Technical Field

The present invention relates to actuation, and more specifically actuation of components of switchable valve train devices of an internal combustion engine.

Background

Internal combustion engines may comprise switchable engine or valve train devices. For example, valve train assemblies may comprise a switchable rocker arm (also referred to as a switchable finger follower) to provide for control of valve actuation by alternating between at least two or more modes of operation (e.g. valve-lift modes). Such rocker arms typically involve multiple bodies, such as an inner arm and an outer arm. These bodies are latched together to provide one mode of operation (e.g. a first valve-lift mode) and are unlatched, and hence can pivot with respect to each other, to provide a second mode of operation (e.g. a second valve-lift mode). Typically, a moveable latch pin is used and actuated and de-actuated to switch between the two modes of operation.

WO 2013/156610 Al [EATON SRL] discloses such a switchable rocker arm with a moveable latch pin. The default position of the latch pin is unlatched, and it is retained in this position using biasing means. When required, the latch pin is actuated to the latched position using an external actuation mechanism based on a leaf spring. When actuation is required, the leaf spring is controlled to rotate a certain amount so as to engage with a roller of the latch pin, and hence push the latch pin into the latched position. In this way, the mode of operation that the switchable rocker arm provided for is controlled, for example, to provide for internal Exhaust Gas Recirculation.

Implementation of actuation of switchable rocker arms can be difficult due to the tight packaging constraints associated with internal combustion engines. Summary

According to a first aspect of the present invention, there is provided an actuation apparatus for actuating a component of a switchable valve train device of an internal combustion engine, the actuation apparatus comprising: a support body for mounting on a cylinder head cover of the internal combustion engine; an actuation lever mounted to the support body for pivotal movement of the actuation lever between a first position for actuation of the component of the switchable valve train device and a second position for allowing de-actuation of the component of the switchable valve train device; and a biasing means arranged to urge the actuation lever from the second position towards the first position; wherein the apparatus is arranged such that, in use, the biasing means becomes biased when an actuation source causes the actuation lever to be in the second position; and when the actuation source attempts to actuate the component when the component of the switchable valve train device is non-actuatable, the biasing means causes the actuation lever to pivot from the second position to the first position, thereby to actuate the component of the switchable valve train device, when the component becomes actuatable again.

The actuation apparatus may be arranged such that, in use, when the actuation attempts to actuate the component and the component of the switchable valve train device is actuatable, the biasing means causes the actuation lever to pivot from the second position to the first position, thereby to actuate the component of the switchable valve train device, substantially immediately.

The actuation lever may be pivotally mounted to the support body at or towards a central portion of the actuation lever, and the biasing means may contact the actuation lever at a first end portion of the actuation lever, thereby to urge pivotal movement of the actuation lever towards the first position. The biasing means may contact the support body and may be arranged to urge the first end portion of the actuation lever away from the support body, thereby to urge pivotal movement of the actuation lever towards the first position.

A second end portion of the actuation lever, on an opposite side of the central portion to the first end portion of the actuation lever, may be arranged to contacting the component of the switchable valve train device.

The actuation apparatus may comprise the cylinder head cover of the internal combustion engine, and the support body may be mounted on the cylinder head cover.

The support body may comprise a main body for mounting the cylinder head cover of the internal combustion engine, and one or more support wings extending from the main body and to which the actuation lever is pivotally mounted.

The actuation apparatus may comprise: a shaft rotatable by the actuation source; and a lobed cam mounted on the shaft; and the apparatus may be arranged such that, in use, the biasing means becomes biased when the actuation source rotates the shaft so that a lobed profile of the lobed cam contacts the actuation lever thereby to cause the actuation lever to pivot from the first position so as to be in the second position.

The apparatus may be arranged such that, in use, the actuation source attempts to actuate the component when the actuation source rotates the shaft so that a base circle of the lobed cam contacts or is orientated towards the actuation lever.

The shaft may be supported by a support portion of the cylinder head cover of the internal combustion engine.

According to a second aspect of the present invention, there is provided a valve train assembly comprising the actuation apparatus according to the first aspect; and the switchable valve train device. The switchable valve train device may be a switchable rocker arm comprising a first body and a second body, and the component of the switchable rocker arm may be a latching arrangement comprising a moveable latch pin for latching the first body and the second body together.

The valve train assembly may be arranged such that, in use, when the actuation lever is moved from the second position to the first position, the actuation lever actuates the latching arrangement of the rocker arm so as to move the latch pin from an unlatched position in which the first body and the second body are unlatched so that the first body and the second body are moveable relative to one another so that the switchable rocker arm is configured for a second mode of operation, to a latched position in which the first body and the second body are latched together so that the switchable rocker arm is configured for a first mode of operation.

The second mode of operation may be cylinder deactivation.

The latching arrangement may comprise a biasing element arranged to urge the latch pin from the latched position to the unlatched position.

Further features and advantages of the invention will become apparent from the following description of examples of the invention which is made with reference to the accompanying drawings.

Brief Description of the Drawings

Figure 1 illustrates schematically a valve train assembly according to an example.

Detailed Description

Referring to Figure 1, a valve train assembly 1 of an internal combustion engine (not shown) comprises an actuation apparatus 200. The actuation apparatus 200 is arranged to actuate a component 4 of a switchable valve train device 2 of the valve train assembly 1. In this example, the switchable valve train device 2 is a switchable rocker arm 2, and the component 4 of the switchable rocker arm 2 is a moveable latching arrangement 4 of the rocker arm 2.

It should be noted that in Figure 1, for economy of representation, the actuation apparatus 200 is shown in perspective view, whereas the rocker arm 2 is shown in cross section. It will be readily appreciated however that in practice, for example as described herein, the rocker arm 2 and the actuation apparatus 200 may be suitably aligned with one another, for example such that the longitudinal axes of the axle 215 and/or the shaft 210 of the actuation apparatus 200 (described in more detail below) are perpendicular to the plane through which the cross section of the rocker arm 2 is taken in the schematic illustration of Figure 1.

The switchable rocker arm 2 is arranged to control opening and closing of a valve (not shown), for example an exhaust valve (not shown), of a cylinder (not shown) of an overall internal combustion engine (not shown). The latching arrangement 4 comprises a moveable latch pin 80 for latching an inner body (not shown) and an outer body 10 of the rocker arm 2 together.

Switchable rocker arms having moveable latch pins are known per se, see e.g. WO 2013/156610 Al [EATON SRL] In this example, the inner body (not shown) and the outer body 10 may be latched together by the moveable latch pin 80 to provide a first mode of operation (e.g. a first valve-lift mode, e.g. a single lift mode where the valve (not shown) is opened for example once per engine cycle, for example to provide for a‘normal’ engine operation mode) and unlatched, and hence can pivot with respect to each other, to provide a second mode of operation (e.g. a second valve-lift mode, e.g. a deactivation mode where the valve (not shown) is not opened during the engine cycle, for example to provide for cylinder deactivation (CD A). Specifically, in this example, the outer body 10 and the inner body (not shown) are pivotably connected together at a pivot axis (not shown). A first end (not shown) of the outer body 10 contacts a valve stem (not shown) of the valve (not shown) and a second end lOa of the outer body 10 contacts a hydraulic lash adjuster (HLA) (not shown). The outer body 10 is arranged to move or pivot about the HLA (not shown).

The rocker arm 2 further comprises at the second end of the outer body 10 the latching arrangement 4 comprising the latch pin 80. The latch pin 80 is slidably received in a bore 51 of the outer body 10 of the rocker arm 2. The latch pin defines a contact surface 53 for engaging with a corresponding surface (not shown) of the inner body (not shown) for latching the inner body (not shown) and the outer body 10 together.

The inner body (not shown) may be provided with an inner body cam follower (not shown), for example, a roller follower (not shown) for following a lift cam (not shown). The outer body 10 may be provided with a pair of roller followers (not shown), for example slider pads (not shown) arranged either side of the roller follower of the inner body (not shown), for contacting a portion of the camshaft (not shown) on which the lift cam (not shown) is mounted.

The latch pin 80 is moveable between a first position in which the outer body 10 and the inner body (not shown) are un-latched and hence can pivot with respect to each other about the pivot axis 12 and a latched position in which the outer body 10 and the inner body (not shown) are latched together and hence can move or pivot about the HLA (not shown) as a single body. For example, when the inner body and the outer body 10 are unlatched and a lobe of a lift cam (not shown) engages the inner body roller follower (not shown), the inner body (not shown) may pivot relative to the outer body against the return spring arrangement (not shown) 10 so as to absorb as“lost motion” the lobe of the lift cam (not shown) and hence no valve event may occur, whereas when the inner body (not shown) and the outer body 10 are latched together the lobe of the lift cam (not shown) engaging the roller follower of the inner body (not shown) may cause the inner body and outer body 10 to pivot about the HLA (not shown) as a single body, which may in turn may cause a valve event to occur. The rocker arm 2 may further comprise a return spring arrangement (not shown) for returning the inner body (not shown) to its rest position after it is has pivoted with respect to the outer body 10.

The latching arrangement 4 comprises a biasing element 11 that biases the latch pin 80 to the unlatched position. Therefore, in a default state, the latch pin is urged by the biasing element 11 to its default, unlatched, position. The biasing element 11 contacts at a first end the outer body 10 of the rocker arm 2 and contacts at a second end a lip 55 of a contact portion 57 through which the latch pin 80 is received and to which the latch pin 80 is connected.

It will be appreciated that in some examples, the rocker arm 2 may be any rocker arm comprising a plurality of bodies that move relative to one another, and which are latched together to provide one mode of operation (valve-lift mode) and are unlatched, and hence can move with respect to each other, to provide a second mode of operation (valve-lift mode). For example, rocker arm 2 may configured for internal Exhaust Gas Recirculation (iEGR), Cylinder Deactivation (CD A), Early Exhaust Valve Opening (EE VO), or the like applications.

The actuation apparatus 200 is for actuating the latching arrangement 4 of the switchable rocker arm 2. For example, actuation of the latching arrangement 4 may be controlled when it is desired to change the mode of operation of the rocker arm 2, for example as described above.

The actuation apparatus 200 comprises a support body 213, an actuation lever 212 mounted to the support body 213 for pivotal movement relative to the support body 213, and a biasing means 214 (also referred to herein as a compliance spring 214). The actuation apparatus 200 also comprises an actuation source (not shown), for example an electrical motor or hydraulic motor or other suitable means, a shaft 210 that is rotatable by the actuation source (not shown), and a lobed cam 211 mounted on the shaft 210.

The actuation lever 212 is mounted to the support body 213 for pivotal movement relative to the support body 213 between a first position (not shown) for actuation of the latching arrangement 4 and a second position (as illustrated in Figure 1) for allowing de- actuation of the latching arrangement 4. The biasing means 214 is arranged to urge or preload the actuation lever 213 from the second position towards the first position.

In overview, and as described in more detail below, the apparatus 200 is arranged such that, in use, the biasing means 214 becomes biased when an actuation source causes the actuation lever 212 to be pivot to the second position; and when the actuation source attempts to actuate the latching arrangement 4 when the latching arrangement 4 is non-actuatable, the biasing means 214 causes the actuation lever 212 to pivot from the second position to the first position, thereby to actuate the latching arrangement 4, when the component 4 becomes actuatable again.

The actuation lever is 212 is pivotally mounted to the support body 213 at or towards a central portion 2l2c of the actuation lever 212. The support body 213 is mounted on (and therefore supported by) a cylinder head cover 217 of the internal combustion engine (not shown). Specifically, the support portion 213 comprises a main body 213a mounted on the cylinder head cover 217 of the internal combustion engine (not shown). The support portion 213 comprises two support wings 219 (only one is visible in Figure 1) extending from the main body 213a and located either side of the actuation lever 212. The actuation lever 212 is pivotally mounted to the support portion 213 via an axle 215 supported by the support wings The biasing means 214 is a coil spring 214 that is supported by a protrusion 220 of the main body 213a. A first end of the biasing means 214 contacts the support body 213, and a second end of the biasing means contacts the actuation lever 212 at a first end portion 212a of the actuation lever 212. The biasing means 214 therefore biases the first end portion 212a of the actuation lever 212 away from the support body 213, thereby urging rotation of the actuation lever 212 towards the first position. A second end portion 212b of the actuation lever 212, located on an opposite side of the central portion 212c to the first end portion 212a of the actuation lever 212, is arranged for contacting the latching arrangement 4 of the rocker arm 2.

The lobed cam 211 mounted on the shaft 210 is aligned with the actuation lever 212 and is arranged for contacting the first end portion 212a of the actuation lever 212. The lobed cam 211 comprises a base circle portion 222 and a lobed profile 224. The shaft is supported by a support portion (not shown) of the cylinder head cover 217 of the internal combustion engine (not shown).

The biasing means 214 becomes biased (i.e. compressed, energised) when the actuation source (not shown) causes the actuation lever 212 to be in the second position. Specifically, when the actuation source (not shown) rotates the shaft 210 such that the lobed profile 224 of the lobed cam 211 contacts or pushes the first end portion 212a of the actuation lever 212, the actuation lever 212 is caused to pivot from the first position so as to be in the second position, which biases the biasing means 214. The latch pin 80 of the latching arrangement 4 may then move under the force of the biasing element 11 of the latching arrangement 4 so that the latch pin 80 is in the unlatched (de-actuated) position.

The actuation source (not shown) may be controlled by a control unit (not shown). The actuation source may be controlled to cause the actuation lever 212 to pivot from the first position so as to be in the second position, for example when the engine control unit (not shown) decides that the latching arrangement 4 is to be de-actuated, for example so that the rocker arm 2 provides for the second mode of operation (e.g. for cylinder deactivation).

When the actuation source (not shown) does not cause the actuation lever 212 to be in the second position (i.e. when actuation of the latching arrangement 4 is desired), the biasing means 214 can cause the actuation lever 212 to pivot from the second position to the first position, thereby to actuate the latching arrangement 4. Specifically, when the shaft 211 is rotated by the actuation source (not shown) such that a base circle 222 of the lobed cam 211 contacts or is orientated towards the actuation lever 212, the actuation lever 212 may (e.g. has the space to) pivot to the first position under the force of the biasing means 214. The biasing means 214 is stronger than the biasing element 11 of the latching arrangement 4 of the rocker arm 2, and hence the biasing means 214 can pivot the actuation lever 212 from the second position to the first portion against the force of the biasing element 11. The actuation source may be controlled to not cause the actuation lever 212 be in the second position (i.e. controlled to attempt to actuate the latching arrangement 4), for example when the engine control unit (not shown) decides that the latching arrangement 4 is to be actuated, for example so that the rocker arm 2 provides for the first mode of operation.

In cases where the latching arrangement 4 is actuatable (i.e. when the latch pin 80 is free to move), when the base circle 222 of the lobed cam 211 contacts or is orientated towards the actuation lever 212, the biasing means 214 expands so as to cause the actuation lever 212 to pivot from the second position to the first position (against the biasing element 11), thereby to actuate the latching arrangement 4. More specifically, when the actuation lever 212 is moved (by the biasing means 214) from the second position to the first position, the actuation lever 212 actuates the latching arrangement 4 of the rocker arm 2 so as to move the latch pin 80 from an unlatched position (in which the inner body and the outer body 10 are unlatched so that the inner body and the outer body 10 are moveable relative to one another so that the switchable rocker arm 2 is configured for the second mode of operation e.g. cylinder deactivation), to a latched position (in which the inner body and the outer body 10 are latched together so that the switchable rocker arm 2 is configured for the first mode of operation e.g. normal engine operation).

In these cases where the latching arrangement 4 is actuatable, the pivoting of the actuation lever 212 under the force of the biasing means 214 from the second position to the first portion may occur substantially immediately, i.e. as soon as the base circle 222 of the lobed cam 211 contacts or is orientated towards the actuation lever 212.

However, in some cases, the latching arrangement may not be actuatable (i.e. non- actuatable), e.g. the latch pin 80 may not be free to move, e.g. may be blocked. For example, the actuation of the latch pin 80 may not be possible immediately due to an engine condition. For example, a lift profile (not shown) of a lift cam (not shown) may be engaged with the roller follower (not shown) of the inner body (not shown) of the rocker arm 2. In this case, the inner body (not shown) will be rotated with respect to the outer body 10, hence blocking the path of the latch pin 80 from moving from the unlatched position to the latched position. In this case, when the base circle 222 of the lobed cam 211 contacts or is orientated towards the actuation lever 212, the biasing means 214 is not able to expand and instead remains compressed as the actuation lever 212 remains in the second position. As soon as (i.e. the instant that) the latching arrangement 4 becomes actuatable again, i.e. as soon as latch pin 80 becomes free to move again (i.e. becomes unblocked, e.g. as soon as the roller follower (not shown) of the inner body (not shown) is engaged with a base circle (not shown) of the lift cam (not shown) and hence the inner body (not shown) is no longer blocking the path of the latch pin 80), the energy stored in the biasing of the biasing means 214 will cause the actuation lever to move from the second position to the first position, thereby actuating the latching arrangement 4. In other words, when the actuation source (not shown) attempts to actuate the latching arrangement 4 (e.g. when the actuation source rotates the shaft 210 so that the base circle 222 of the lobed cam 211 contacts or is orientated towards the actuation lever 212), and the latching arrangement is non-actuatable (e.g. the latch pin 80 is prevented from moving to the unlatched position to the latched position) the biasing means 214 causes the actuation lever 212 to pivot from the second position to the first position, thereby to actuate the latching arrangement 4, when (e.g. as soon as) the component becomes actuatable again.

As a result, the latch pin 80 is moved from the unlatched position to the latched position, hence latching the inner body (not shown) and the outer body 10 together, hence switching the rocker arm 2 from the second mode of operation (e.g. cylinder deactivation) to the first mode of operation (e.g. normal operation) as described above.

As a result, regardless of the blocked or unblocked state of the latch pin 80 (i.e. regardless of whether the latching arrangement 4 is actuatable or non-actuatable), the latching arrangement 4 may be actuated as soon as it is physically possible to do so, i.e. as soon as the rocker arm 2 is not in a state which blocks actuation. This may be referred to as a compliance function of the actuation apparatus. This reduces the need to control the timing of the actuation to be synchronised with the engine cycle, and hence may provide for simpler and more efficient control.

At a later stage, the actuation source (not shown) may once again rotate the shaft 210 so that the lobe profile 224 of the lobed cam 211 contacts the first end 212a of the actuation lever 212 (e.g. when de-actuation of the latching arrangement is again required) which causes the actuation lever 212 to rotate, against the biasing means 214, from the first position to the second position. As a result, the second end 212b of the actuation lever no longer exerts a substantial force to the latch pin 80. As a result, the latch pin 80 may move from the latched position to the unlatched position under the force of the biasing element 11 , hence the latch pin 80 no longer latches the inner body (not shown) and the outer body 10 together, and hence the rocker arm 2 is switched from the first mode of operation (e.g. normal operation) to the second mode of operation (e.g. cylinder deactivation).

As mentioned above, the actuation apparatus 200 is installed on an internal combustion engine cylinder head cover 217. That is, the support body 213 and/or the shaft 210 may be supported by (installed on, mounted on) the cylinder head cover 217 or a portion thereof.

According to the above example therefore, the actuation lever 212 is urged or preloaded by the biasing means (compliance spring) 214 mounted on the support 213 so as to assure that the latching arrangement 4 of the rocker arm 2 is in the latched position when the actuation lever 212 contacts with a base circle 222 of the cam 211, and movement of the latching arrangement 4 to the unlatched position is allowed for when the lobed profile 224 of the cam 211 pushes the actuation lever 212. Hence simple, efficient and flexible control of a switchable rocker arm (for example control of switching between normal operation mode and cylinder deactivation mode) may be provided for, without the need for synchronisation of the control with the engine condition.

Having the actuation lever 212 and/or the biasing means 214 mounted on the support body 213 may allow for simple installation onto the cylinder head cover, which may allow for more efficient assembly. In the example illustrated in Figure 1 , the valve train assembly 1 comprises one rocker arm 2 having a latching arrangement 4. In other examples (not illustrated) there may be a plurality of rocker arms 2 each having a respective latching arrangement 4. It will be appreciated that in these examples the actuation apparatus 200 may comprise a plurality of support bodies 213, actuation levers 212, biasing means 214, and cams 211, each associated with a respective one of the plurality of latching arrangements 4. In some examples, each of the plurality of cams 211 may be mounted on a common shaft 210 rotatable by the actuation source (as described above), and hence allow for actuation of the respective latching arrangements 4 in common. Each of the plurality of support bodies 213 (each with their associated actuation lever 212 and compliance spring 214) may be mounted on a common support (not shown) for mounting to the cylinder head cover. This may allow for simple installation onto the cylinder head cover, which may allow for more efficient assembly

Having the shaft 210 and/or the support body 213 mounted on the cylinder head cover 217 may allow for improved packaging of the switchable rocker arm functionality in the internal combustion engine. For example, having the shaft 210 mounted on the cylinder head cover 217 may reduce packaging constraint issues for example as compared to having the shaft 210 installed into the cylinder head itself and/or for example as compared to having the lobed cams 211 directly contacting latching arrangements of the rocker arms 2. This may also reduce the need to adapt the cylinder head itself to accommodate the shaft 210 and hence may allow for simpler manufacturing of the cylinder head. Having a compliance functionality provided by the biasing means 214 mounted to the support body 213 mounted to the cylinder head cover 217 may also provide for improved packaging for example as compared to providing the compliance functionality in the actuation arrangements 4 of the rocker arms 2 themselves. For example, not having to provide compliance functionality in the rocker arms 2 themselves allows for the packaging footprint of the rocker arms to be reduced.

All of the above examples are to be understood as illustrative examples only. It is to be understood that any feature described in relation to any one example may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the examples, or any combination of any other of the examples. Furthermore, equivalents and modifications not described above may also be employed without departing from the scope of the invention, which is defined in the accompanying claims.

Reference Signs List

1 valve train assembly

2 rocker arm

4 latching arrangement

10 outer body

lOa second end

11 biasing element

55 lip

57 contact portion

80 latch pin

200 actuation apparatus

210 shaft

211 cam

212 actuation lever

2l2a first end portion

2l2b second end portion

2l2c central portion

213 support body

2l3a main body

214 biasing means (compliance spring)

215 axle

217 cylinder head cover

219 support wing

220 protrusion

222 base circle

224 lobed profile