The invention relates to an actuation arrangement for a valve train assembly for an internal combustion engine, and more specifically to an actuation arrangement to allow control of dual body rocker arms on a per group basis. Background

Internal combustion engines may comprise switchable engine or valve train components. For example, valve train assemblies may comprise a switchable rocker arm to provide for control of valve actuation (for example exhaust or inlet valve actuation and/or de-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 by a latching system comprising a movable latch pin to provide one mode of operation (e.g. a first valve-lift mode (e.g. normal engine combustion 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 (e.g. valve de-activation mode). Typically, the moveable latch pin is used and actuated and de-actuated to switch between the two modes of operation.

Summary

According to a first aspect of the present invention, there is provided the actuation arrangement of claim 1.

According to a second aspect of the present invention, there is provided the valve train assembly of claim 11. List of Figures

The invention will be described, by way of example only, with reference to the accompanying figures, of which: Figure 1 illustrates schematically a perspective view of a valve train assembly; Figure 2 illustrates schematically a cross sectional view of an actuation arrangement according to a first example; and

Figure 3 illustrates schematically a cross sectional view of an actuation arrangement according to a second example.

Description

Referring to Figure 1, there is illustrated a valve train assembly 100 comprising four pairs 101 to 104 of rocker arms 1, and an actuation arrangement 110 for actuating latching arrangements 9 of each rocker arm 1.

In the example of Figure 1, each respective pair of rocker arms 101 to 104 is for controlling a pair of valves (e.g. exhaust or inlet) (not shown) on a respective cylinder (not shown) of an internal combustion engine (not shown) (e.g. the arrangement relates to a 4-cylinder engine in this example).

Each dual body rocker arm 1 comprises an outer body 3 and an inner body 5 that are pivotably connected together at a pivot axis 7. The latching arrangement 9 of each rocker arm 1 comprises a latch pin (not visible) slidably supported in a bore (not visible) in the outer body 3 and which can be urged between a first configuration in which the latch pin (not visible) latches the outer body 3 and the inner body 5 together and a second configuration in which the outer body 3 and the inner body 5 are unlatched. In this example, the latching arrangement 9 is biased to the unlatched configuration by a return spring 21.

In the first configuration, the outer body 3 and the inner body 5 are latched together and hence can move or pivot about a pivot point (not visible) as a single body so that the that rocker arm 1 provides a first primary function, for example, an engine valve (not shown) that it controls is activated as a result of the rocker arm 1 pivoting as a whole about a pivot point (e.g. about a Hydraulic lash adjuster) and exerting an opening force on the valve (not shown). In the second configuration, the outer body 3 and the inner body 5 are un-latched so that the inner body 5, for example, can pivot freely with respect to the outer body 3 about the pivot axis 7 so that rocker arm 1 provides a second secondary function, for example, the valve it controls is de-activated (e.g. to provide cylinder de-activation) as a result of lost motion absorbed by the inner body 5 pivoting freely with respect to the outer body 3 and hence no opening force being applied to the valve (not shown).

The inner body 5 is provided with an inner body cam follower 17, in this example, a roller follower 17 rotatably mounted (for example with bearings) on an axle 19 for following an auxiliary cam profile (not shown) on a cam shaft (not shown) and the outer body 3 is provided with a pair of cam followers, in this example a pair of slider pads, arranged either side of the roller follower 17 for following a pair of primary cam profiles (not shown) mounted on the cam shaft (not shown). The rocker arm 1 further comprises a return spring arrangement 20 for biasing the inner body 5 to its rest position after it is has pivoted with respect to the outer body 3.

Although a particular example rocker arm 1 is described above, it will be appreciated that each dual body rocker arm 1 may be any switchable rocker arm arranged to provide for control of valve actuation (for example exhaust or inlet valve actuation and/or de-actuation) by alternating between at least two modes of operation (e.g. valve-lift modes). For example, the rocker arm 1 may be any dual body rocker arm 1 having a first body 3 and a second body 5 that may be latched together by a latching arrangement 9 to provide one mode of operation (e.g. a first valve-lift mode (e.g. normal engine combustion mode) and that may be 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. valve de-activation mode).

In this example, the actuation arrangement 110 comprises an elongate shaft 112 that is rotatable by an actuator 114, for example an electric motor 114. The actuation arrangement 110 comprises a plurality of components 116, in this example, selector cams 116, one for each rocker arm 1, mounted on the shaft 112 for operating the latching arrangements 9. Each selector cam 116 comprises a lobe profile 117 and a base circle 118.

The actuator 114 is able to move or rotate the shaft 112 between first and second configurations. In the first configuration, the cam lobe profiles 117 of the selector cams 116 push or act on the latching arrangements 9 (as illustrated in Figure 1) causing the latch pins (not visible) to be in the latched position. In the second configuration (not illustrated), the cam lobe profiles 117 of the selector cams 116 do not act on the latching arrangements 9 of the rocker arms 1 allowing the return springs 21 to cause the latch pins 11 to be in the un-latched position.

It may be desirable to provide an actuation arrangement able to allow control some of the rocker arms 1 independently from others of the rocker arms 2, for example to allow control the function provided by some of the rocker arms 1 independently from the control of the function of other of the rocker arms 1.

Figure 2 illustrates schematically a valve train assembly 200 comprising an actuation arrangement 210 according to a first example, that allows such control. Similarly to the above actuation arrangement 110 described with reference to Figure 1, the actuation arrangement 210 of this first example is for actuating a plurality of latching arrangements (not shown in Figure 2) of a respective plurality of dual body rocker arms (not shown in Figure 2) of a valve train assembly 200 of an internal combustion engine (not shown). Each dual body rocker arm (not shown) may be the same or similar to the rocker arm 1 described above. For example, each dual body rocker arm (not shown) may comprise a first body, a second body, and a latching arrangement for latching and unlatching the first body and the second body.

However, in this example, the actuation arrangement 210 comprises a first shaft 250 comprising one or more first selector cams 116a for controlling the latching arrangements (not shown in Figure 2) of a first group of one or more of the dual body rocker arms (not shown in Figure 2), and a second shaft 252 comprising one or more second selector cams 116b for controlling the latching arrangements (not shown in Figure 2) of a second group of one or more of the dual body rocker arms (not shown in Figure 2). The first shaft 250 and the second shaft 252 are controllable to rotate independently of one another, thereby to allow control of the latching arrangements of the dual body rocker arms on a per group basis.

The first shaft 250 and the second shaft 252 are generally elongate. A first portion 250a of the first shaft 250 is received in the second shaft 252. Specifically, the second shaft 252 defines a channel 254 extending therethrough in which the first portion 250a of the first shaft 250 is received. The first portion 250a of the first shaft 250 extends through the entire length of the channel 254. The second shaft 252 is generally tube shaped, and the channel 254 defined buy the second shaft 252 is generally cylindrical. The first portion 250a of the first shaft 250 is also generally cylindrical and is arranged to fit into the channel 254 in the second shaft 253 and to freely rotate therein. The first shaft 250 and the second shaft 252 are substantially co-axial (see common axis A).

A second portion 250b of the first shaft 250 is not received within the second shaft 252 and extends away from channel 254 of the second shaft 252. The second portion 250b of the first shaft 250 has a diameter larger than that of the first portion 250a of the first shaft 250. An outer diameter of the second portion 250b of the first shaft 250 may be the same or similar to an outer diameter of the second shaft 252.

In this example, the second portion 250b of the first shaft 250 comprises the one or more (in this example six) first selector cams 116a for controlling the latching arrangements (not shown in Figure 2) of the first group of one or more (in this example six) respective dual body rocker arms (this example relates to a 6-cylinder engine) (not shown in Figure 2). The second shaft 252 comprises six second selector cams 116b for controlling the latching arrangements of the second group (in this example 6) respective dual body rocker arms (not shown in Figure 2).

Each of the dual body rocker arms (not shown) are for controlling a valve (not shown) of an internal combustion engine (not shown). In this example, the first group comprises three pairs of rocker arms (not shown), each respective pair for controlling a pair of valves (e.g. exhaust or inlet) (not shown) on a respective cylinder (not shown) of a first group of three cylinders of an internal combustion engine. Similarly, the second group comprises three pairs of rocker arms each respective pair for controlling a pair of valves (e.g. exhaust or inlet) (not shown) on a respective cylinder (not shown) of a second group of three cylinders of an internal combustion engine, (e.g. the arrangement relates to a 6-cylinder engine in this example). It will be appreciated that although in this example there are six cylinders, this need not necessarily be the case and in other examples, the first group may comprises one or more pairs of dual body rocker arms each for controlling valves of a first group of one or more cylinders of the internal combustion engine, and the second group may comprise one or more pairs of dual body rocker arms each for controlling valves of a second group of one or more cylinders of the internal combustion engine. The actuation arrangement 210 comprises a first actuation source 260 connected to the first shaft 250 and arranged to rotate the first shaft 250, and a second actuation source 262 connected to the second shaft 252 and arranged to rotate the second shaft 252. The first actuation 260 source is mechanically connected to the first portion 250a of the first shaft. The first 260 and second 262 actuation source are located on a side of the second shaft 252 opposite to the second portion 250b of the first shaft 250. The first portion 250a of the first shaft 250 extends out beyond the second shaft 252 for connection to the first actuation source 260.

In this example, the first actuation source 260 comprises a first two-step or ON/OFF actuator (not shown), and the second actuation source 262 comprises a second two- step or ON/OFF actuator (not shown). The actuators may be or comprise for example electromagnetic or hydraulic actuators. The first actuation source 260 and the second actuation source 262 may form an integral unit. In use, when it desired that a function provided by the first group of rocker arms is to be changed, but that a function provided by the second group of rocker arms is not to be changed, the first actuation source 260 may be controlled (for example by an engine management system (not shown)) to rotate the first shaft 250 so as to change the orientation of the first selector cams 116a with respect to each of the latching arrangements (not shown) of the first group of rocker arms (not shown), thereby causing the latching arrangements to move from one to the other of the latched configuration and the unlatched configuration, thereby to change the function (e.g. for example a valve lift mode) of the first group of rocker arms (not shown).

Similarly, when it desired that a function provided by the second group of rocker arms is to be changed, but that a function provided by the first group of rocker arms is not to be changed, the second actuation source 262 may be controlled (for example by an engine management system (not shown)) to rotate the second shaft 252 so as to change the orientation of the second selector cams 116b with respect to each of the latching arrangements of the second group of rocker arms, thereby causing the latching arrangements to move from one to the other of the latched configuration and the unlatched configuration, thereby to change the function (e.g. for example a valve lift mode) of the second group of rocker arms (not shown).

When it desired that a function provided by the first and second group of rocker arms is to be changed, the first 260 and second 262 actuation source may be both controlled (for example by an engine management system (not shown)) to rotate the first shaft 250 and the second shaft 252, respectively, so as to change the orientation of the first 116a and second 166b selector cams with respect to each of the latching arrangements of the first and second group of rocker arms, thereby causing the latching arrangements to move from one to the other of the latched configuration and the unlatched configuration, thereby to change the function (e.g. for example a valve lift mode) of the first and second group of rocker arms (not shown).

The actuation arrangement 210 therefore enables the use of a simple actuator, incorporating two basic ON/OFF actuators 260, 262 integrated into a single block, delivering a multiple step actuation control while solving the problem of the integration in the engine. As compared to the example of Figure 1, the actuation shaft 250, 252 and actuation source in this example are split to achieve multi-step type actuation control using two simple ON/OFF actuators 260, 262. This may provide a simpler and more efficient solution, for example as compared to using a single shaft with differently shaped lobes and using a complex electric actuator (for example a multi-step actuator or stepper motor).

Referring now to Figure 3, there is shown a valve train assembly 300 comprising an actuation arrangement 310 according to a second example. The second example is similar to the first example described with reference to Figure 2. Features which are the same or similar to as in the first example will not be described in detail again. Like features are given like reference signs.

As with the first example described with reference to Figure 2, in this second example with reference to Figure 3, the actuation arrangement 310 comprises a first shaft 250 comprising six first selector cams 116a for controlling the latching arrangements of a first group of six (e.g. three pairs of) dual body rocker arms (not shown); and a second shaft 252 comprising six second selector cams 116b for controlling the latching arrangements of a second group of six (e.g. three pairs of) dual body rocker arms; where at least a portion of the first shaft 250 is received in the second shaft 252 and the first shaft 250 and the second shaft 350 are controllable to rotate independently of one another, by a first 360 and second 362 actuation source respectively, thereby to allow control of the latching arrangements of the dual body rocker arms (not shown) on a per group basis.

However, in this second example, the first actuation source 360 is or comprises a first torque motor 360 and the second actuation source 362 is or comprises a second torque motor 362. The first 360 and second 362 torque motors may each be a two-step motor. The first 360 and second 362 torque motors are coaxial (se e.g. axis A in Figure 3)

The first torque motor 360 is connected to the first shaft 250 and is arranged to rotate the first shaft 250, and the second torque motor 362 is connected to the second shaft 252 and is arranged to rotate the second shaft 252. Specifically, the first torque motor 360 comprises a first rotor 360a and a first stator 360b. The second torque motor 362 comprises a second rotor 362a and a second stator 362b. The first 360b and second 362b stators comprise bobbin packs. The bobbin packs may be as known per se in electric motors. The first rotor 360a of the first torque motor 260 is connected to the first shaft 250, and the second rotor 362a of the second torque motor 362 is connected to the second shaft 252. The first torque motor 350 is coaxial with the second torque motor 352.

A portion 250c of the first shaft 250 extends through the second torque motor 362, thereby to be connected to the first torque motor 360. Specifically, the second rotor 362a and the second stator 362b of the second torque motor 362 define a substantially cylindrical cavity 362c that is coaxial with the second shaft 252. The portion 250c of the first shaft 250 extends out beyond the channel 254 of the second shaft 252, and through the cylindrical cavity 362c, for connection with the first rotor 360a of the first torque motor 360. In this example, the first rotor 360a of the first torque motor 360 is on a side of the first torque motor 360 facing away from the second shaft 252, and the second rotor 362a of the second torque motor 362 is on a side of the second torque motor 362 facing towards the second shaft 252.

The first torque motor 360 and the second torque motor 362 are packaged or housed in a single body 370. This may be a space efficient arrangement, and allow for more convenient installation of the actuator 370 onto the engine (not shown).

Similarly to as described above for the first example, in this second example, the first torque motor 360 and the second torque motor 362 may be controlled independently (for example by an engine management system (not shown)) similarly to as described above, to allow independent control of the rotation of the first shaft 250 and the second shaft 252, and hence for independent control the latching arrangements of a first and second group of rocker arms controlling valves of a respective first and second group of cylinders (not shown). Each rocker arm 1 in any of the above examples may provide for any switchable valve operating mode, for example an exhaust deactivation mode, variable valve timing mode, exhaust gas recirculation mode, compression brake mode etc. All of the above examples are to be understood as illustrative examples of the invention 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 Rocker arm

3 outer body

5 inner body

7 pivot axis

9 latching arrangement

17 roller follower

19 axis

20 return spring arrangement

21 return spring

100, 200, 300 valve train assembly

101, 102, 103, 104 pairs of rocker arms

110, 210, 310 actuation arrangement

112 shaft

114 actuator

116 selector cam

116a first selector cam

116b second selector cam

117 lobed profile

118 base circle first shaft

a first portion

b second portionc third portion

second shaft channel

, 360 first actuation source, 362 second actuation sourcea, 362b rotor

b, 362b stator

c cavity

housing