Method for cylinder constant recharging

Abstract

A valve train assembly for actuating an intake valve. A latch assembly is configured to selectively couple a late intake valve roller to a main rocker body. A lost motion assembly is configured to bias the late intake valve roller to a first position wherein the latch assembly is movable between a latched position and an unlatched position. The lost motion assembly is configured to allow the late intake valve roller to move a predetermined maximum distance when the latch assembly is in the unlatched position. When the latch assembly is in the unlatched position and after the late intake valve roller has moved the predetermined maximum distance, a portion of a late intake valve lift profile of a cam applies additional motion to the late intake valve roller such that the late intake valve roller and the main rocker body are coupled together and move as a unitary body.

Description

METHOD FOR CYLINDER CONSTANT RECHARGINGPriority

[0001] This application claims the benefit of priority of provisional U.S. patent application Ser. No. 63 / 511,410, filed June 30, 2024, the contents of which are incorporated herein by reference in their entirety.Field

[0002] The subject application relates, in general, to a rocker arm assembly for use in a combustion engine wherein the rocker arm assembly includes two latch assemblies for activating or deactivating two rollers of the rocker arm assembly. More particularly, this application relates to a rocker arm assembly having a first latch assembly and a second latch assembly, the latch assemblies being configured to selectively couple a first roller and a second roller to a main rocker body.Background

[0003] Cylinder Deactivation (CD A) encompasses engine management control methods defined by shutting off fueling and valve motion to select cylinders of a multicylinder engine. CDA is applied to internal combustion engines to help improve performance. For example, CDA reduces fuel consumption and increases exhaust temperature, also known as aftertreatment thermal management. During CDA, gas is trapped inside an engine cylinder. Over time, the pressure of the gas dissipates because of leakage in the cylinder and therefore the gas temperature drops. Eventually, a negative pressure develops in the cylinder which can lead to unwanted oil leaks into the combustion engine. The presence of oil in the cylinder and the low temperature can be harmful to engine operation in terms of emissions and in extreme cases can lead to formation of crystals from vapors inside the cylinder. The foregoing problems are particularly obvious when intake valves are deactivated before exhaust valves. It is desirable to recharge the gas in the cylinder by means of a small valve opening during CDA.

[0004] The present application provides a system for implementing small valve opening in internal combustion engines having a late intake valve closing (LIVC) system in combination with CDA.Summary of the Invention

[0005] There is provided a valve train assembly for actuating an intake valve. The valve train assembly includes a rocker arm assembly having a main rocker body with a valve end. A first latch assembly is configured to selectively couple a main intake valve roller to the main rocker body, the first latch assembly has a latched position wherein the main intake valve roller is coupled to the main rocker body and an unlatched position wherein the main intake valve roller is uncoupled from the main rocker body. A first lost motion assembly is configured to bias the main intake valve roller to a first position wherein the first latch assembly is movable between the latched position and the unlatched position. A second latch assembly is configured to selectively couple a late intake valve roller to the main rocker body. The second latch assembly has a latched position wherein the late intake valve roller is coupled to the main rocker body and an unlatched position wherein the late intake valve roller is uncoupled from the main rocker body. A second lost motion assembly is configured to bias the late intake valve roller to a first position wherein the second latch assembly is movable between the latched position and the unlatched position. The second lost motion assembly is configured to allow the late intake valve roller to move a predetermined maximum distance relative to the main rocker body when the second latch assembly is in the unlatched position. A first cam is configured to engage the main intake valve roller wherein the first cam has a main intake valve lift profile. A second cam is configured to engage the late intake valve roller wherein, when the first latch assembly and the second latch assembly are in the unlatched position and after the late intake valve roller has moved the predetermined maximum distance, a portion of a late intake valve lift profile of the second cam applies additional motion to the late intake valve roller such that the late intake valve roller and the main rocker body are coupled together and move as a unitary body.

[0006] In the foregoing valve train assembly, a maximum lift of the late intake valve lift profile exceeds a maximum lift of the main intake valve lift profile by a predetermined height.

[0007] In the foregoing valve train assembly, a first lost motion spring of the first lost motion assembly is secured to the main rocker body at one end and to a bracket holding the main intake valve roller at a second end, and a second lost motion spring of the second lost motion assembly is secured to the main rocker body at one end and to a bracket holding the late intake valve roller at a second end.

[0008] In the foregoing valve train assembly, when the first latch assembly and the second latch assembly are unlatched, a lift of the second cam compresses the second lostmotion spring.

[0009] In the foregoing valve train assembly, during a cylinder deactivation mode the first latch assembly and the second latch assembly are in the unlatched positions.

[0010] In the foregoing valve train assembly, when the first latch assembly is in the latched position, the main intake valve roller and the main rocker body pivot as a unitary body.

[0011] In the foregoing valve train assembly, when the second latch assembly is in the latched position, the late intake valve roller and the main rocker body pivot as a unitary body.

[0012] In the foregoing valve train assembly, during a late intake valve closing mode, the first latch assembly and the second latch assembly are in the latched positions.

[0013] In the foregoing valve train assembly, when both the first latch assembly and the second latch assembly are in the latched position, a displacement applied to the valve end of the main rocker body is a greater of the main intake valve lift profile and the late intake valve lift profile.

[0014] There is further provided, a valve train assembly for actuating an intake valve. The valve train assembly includes a rocker arm assembly having a main rocker body. A latch assembly is configured to selectively couple a late intake valve roller to the main rocker body. The latch assembly has a latched position wherein the late intake valve roller is coupled to the main rocker body and an unlatched position wherein the late intake valve roller is uncoupled from the main rocker body. A lost motion assembly is configured to bias the late intake valve roller to a first position wherein the latch assembly is movable between the latched position and the unlatched position. The lost motion assembly is configured to allow the late intake valve roller to move a predetermined maximum distance when the latch assembly is in the unlatched position. A cam is configured to engage the late intake valve roller. When the latch assembly is in the unlatched position and after the late intake valve roller has moved the predetermined maximum distance, a portion of a late intake valve lift profile of the cam applies additional motion to the late intake valve roller such that the late intake valve roller and the main rocker body are coupled together and move as a unitary body.

[0015] In the foregoing valve train assembly, the rocker arm assembly further includes a second latch assembly configured to selectively couple a main intake valve roller to the main rocker body. The second latch assembly has a latched position wherein the main intake valve roller is coupled to the main rocker body and an unlatched position whereinthe main intake valve roller is uncoupled from the main rocker body. A second lost motion assembly is configured to bias the main intake valve roller to a first position wherein the second latch assembly is movable between the latched position and the unlatched position. A second cam is configured to engage the main intake valve roller wherein the second cam has a main intake valve lift profile.Brief Description of the Drawings

[0016] FIG. 1 A is a side perspective view of a rocker arm assembly for an engine;

[0017] FIG. IB is a section view of a latch pin assembly of the rocker arm assembly of FIG. 1A;

[0018] FIG. 2 illustrates lift profiles for a main intake valve lift and a LIVC lift of a valve train assembly including the rocker arm assembly of FIG. 1 A;

[0019] FIG. 3 illustrates lift profiles for a main intake valve lift and a modified LIVC lift of the valve train assembly of FIG. 1 A, according to one embodiment of the present invention;

[0020] FIG. 4 illustrates lift profiles of the main intake valve lift and the modified LIVC lift, wherein the main intake valve lift is active and the modified LIVC lift is in lost motion;

[0021] FIG. 5 illustrates lift profiles of the main intake valve lift and the modified LIVC lift, wherein both the main intake valve lift and the modified LIVC lift are active;

[0022] FIG. 6 illustrates lift profiles of the main intake valve lift and the modified LIVC lift, wherein both the main intake valve lift and the modified LIVC lift are in lost motion; and

[0023] FIG. 7 illustrates lift profiles of the main intake valve lift and the modified LIVC lift, wherein the main intake valve lift is in lost motion and the modified LIVC lift is active.Detailed Description

[0024] The following presents a description of the disclosure; however, aspects may be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Furthermore, the following examples may be provided alone or in combination with one or any combination of the examples discussed herein. Directional references such as “left” and “right” are for ease of reference to the figures.

[0025] Referring to FIG. 1 A, a rocker arm assembly 10 and cams 22, 32 of a valvetrain assembly 1 are shown. The rocker arm assembly 10 includes a main rocker body 11. The main rocker body 11 includes a rocker shaft bore 12, a valve end 13 and a cam end 14. The rocker shaft bore 12 is dimensioned and configured to receive a rocker shaft (not shown) for allowing the main rocker body 11 to pivot thereon. The valve end 13 is configured to engage a valve stem or valve bridge (not shown). The cam end 14 of the main rocker body 11 is configured to selectively engage the first and second cams 22, 32 of the valve train assembly 1 based on a condition of their respective lost motion assemblies 20, 30.

[0026] The first lost motion assembly 20 and the second lost motion assembly 30 are provided for biasing their respective rollers 21, 31 to a first position. The first lost motion assembly 20 includes a first lost motion spring 16 and a first bracket 18. One end of the first lost motion spring 16 is secured to the main rocker body 11 at a first mount 16a and an opposite end of the first lost motion spring 16 is secured to the first bracket 18. The main intake valve roller 21 is rotatably attached to the first bracket 18. The first lost motion spring 16 is configured to bias the first bracket 18 and the corresponding main intake valve roller 21 to the first position wherein a first latch assembly 40 is able to move between a latched position and an unlatched position, as described in detail below.

[0027] The second lost motion assembly 30 includes a second lost motion spring 17 and a second bracket 19. One end of the second lost motion spring 17 is secured to the main rocker body 11 at a second mount 17a and an opposite end of the second lost motion spring 17 is secured to the second bracket 19. The late intake valve roller 31 is rotatably attached to the second bracket 19. The second lost motion spring 17 is configured to bias the second bracket 19 and the corresponding late intake valve roller 31 to the first position wherein a second latch assembly 50 is able to move between a latched position and an unlatched position, as described in detail below. The second lost motion assembly 30 has a maximum lost motion stroke LMMAX that the second bracket (and the late intake valve roller 31 attached thereto) can move relative to the main rocker body 11 when the second latch assembly 50 is in the unlatched position, as described in detail below.

[0028] The rocker arm assembly 10 is configured to actuate an intake valve (not shown). The main intake valve roller 21 is dimensioned and positioned to engage the first cam 22, while the late intake valve roller 31 is dimensioned and positioned to engage the second cam 32. The first and second cams 22, 32 may be, for example, a rotatable body provided with at least one protrusion. The cam profiles are configured to convert rotational movement of the first and second cams 22, 32 to rotational movement of the main rockerbody 11 and lateral movement of valves (not shown). The cam profiles include apexes 22a, 32a that when viewed with the first and second cams 22, 32 as a profile, have a height 22b, 32b defined as a distance from a base circle of the first and second cams 22, 32 to the apex 22a, 32a.

[0029] The rotation of the first and second cams 22, 32 is synchronized with the motion of a corresponding piston (not shown), in particular, with the piston moving between a top dead center position and a bottom dead center position in a piston chamber (not shown). The first cam 22 has a main intake valve lift profile, and the second cam 32 has a LIVC lift profile. The foregoing profiles are discussed in detail further below.

[0030] The first latch assembly 40 for the main intake valve roller 21 may be used for selectively coupling and decoupling the main intake valve roller 21 and the main rocker body 11 to and from each other. Referring to FIG. 1 A, the first latch assembly 40 is shown and described below. The description for the first latch assembly 40 applies equally to the second latch assembly 50 and is not repeated here below for brevity.

[0031] The first latch assembly 40 includes a latch pin 40a, an actuation piston 40b, a latch piston 40c, a spring 40d, and first and second caps 40e, 40f. The latch pin 40a is dimensioned and positioned to be partially received in the main rocker body 11. The actuation piston 40b is positioned between the first cap 40e and the latch pin 40a, and the latch piston 40c is positioned adjacent an opposite end of the latch pin 40a. The spring 40d is compressed between the latch piston 40c and the second cap 40f to bias the latch piston 40c, the latch pin 40a, and the actuation piston 40b toward the first cap 40e.

[0032] When the first latch assembly 40 is in the latched position, the latch pin 40a is partially disposed in both the main rocker body 11 and the first bracket 18 such that the main intake valve roller 21 and the main rocker body 11 are coupled to each other. In this latched condition, the first bracket 18, the main intake valve roller 21 and the main rocker body 11 pivot as a unitary body. Further, in this latched position, the lift profile of the first cam 22 is applied to the main intake valve roller 21 such that the first bracket 18, the main intake valve roller 21 and the main rocker body 11 pivot together about the main rocker shaft (not shown).

[0033] To unlatch the first latch assembly 40, pressurized fluid is supplied to a space between the first cap 40e and the actuation piston 40b to force the actuation piston 40b to move toward the second cap 40f. As the actuation piston 40b moves, the latch pin 40a and the latch piston 40c are forced toward the second cap 40f thereby compressing the spring 40d. Once the latch pin 40a is completely within the first bracket 18, the first bracket18, the main intake valve roller 21 and the main rocker body 11 are decoupled such that the motion of the main intake valve roller 21 causes the first lost motion spring 16 to be compressed. As such, the motion of the first cam 22 is not applied to the main rocker body 11. This is referred to as “lost motion.”

[0034] The second latch assembly 50 for the late intake valve roller 31 may be used for selectively coupling and decoupling the second bracket 19, the late intake valve roller 31 and the main rocker body 11 to and from each other. The second latch assembly 50 includes the same components described in detail above for the first latch assembly 40 which operate in the same manner as described above for the first latch assembly 40 except applied to the late intake valve roller 31.

[0035] When the second latch assembly 50 is in the latched position, the second bracket 19, the late intake valve roller 31 and the main rocker body 11 are coupled to each other so that they pivot as a unitary body when the cam 32 moves the late intake valve roller 31. In this latched position, the lift profile of the second cam 32 is applied to the late intake valve roller 31 such that the second bracket 19, the late intake valve roller 31 and the main rocker body 11 pivot together about the main rocker shaft.

[0036] When the second latch assembly 50 is unlatched, the second bracket 19, the late intake valve roller 31 and the main rocker body 11 are decoupled such that the motion of the late intake valve roller 31 causes the second lost motion spring 17 to be compressed. As such, the motion of the second cam 32 is not applied to the main rocker body 11. This is referred to as “lost motion.”

[0037] When the first and second latch assemblies 40, 50 are both latched, the main intake valve roller 21 and the late intake valve roller 31 are both coupled with the main rocker body 11 and pivot as a unitary body. The displacement applied to the valve (not shown) at the valve end 13 will be the greater of a lift of the first cam 22 and the second cam 32 at any cam angle.

[0038] FIGS. 2-7 provide graphical illustrations for comparing the relative heights of the lift profiles. In the embodiments illustrated, the ratio of the cam lift profiles to the actually lift experienced at the valve end 13 of the main rocker body 11 is 1 : 1. It is contemplated that in actual application, the ratio may not be 1: 1. As illustrated in FIG. 2, conventionally, a maximum lift 2L of the late intake valve roller 31 is equal to a maximum lift 2M of the main intake valve roller 21.

[0039] The present application provides a modified lift profile 3b on the second cam 32 to allow for a constant recharge valve lift when the rocker arm assembly 10 is inCDA mode. Referring to FIG. 3, the modified lift profile 3b of the second cam 32 has a portion 3 c that exceeds the maximum lost motion stroke LMMAX of the second lost motion assembly 30. In other words, when the second latch assembly 50 is unlatched, the lift of the second cam 32 with the modified lift profile 3b causes the second bracket 19 (and the late intake valve roller 31 attached thereto) to compress the second lost motion spring 17. The second bracket 19 is designed so that the maximum distance it can move relative to the main rocker body 11 is the maximum lost motion stroke LMMAX. Once the second bracket 19 has moved the distance of the maximum lost motion stroke LMMAX, the second bracket 19 engages the main rocker body 11, i.e., it is recoupled to the main rocker body 11, such that any additional lift provided by the second cam 32 is applied to the main rocker body 11, the late intake valve roller 31 and the second bracket 19 as a unitary body. The maximum lost motion stroke LMMAX is selected to be greater than a maximum height of the main intake lift profile 2a.

[0040] Referring to FIG. 4, an illustration is provided for the main intake lift profile 2a and the modified lift profile 3b during normal operation when the first latch assembly 40 is latched and the second latch assembly 50 is unlatched. When the first latch assembly 40 is latched and the second latch assembly 50 is unlatched, the main intake lift profile 2a is applied to the main intake valve roller 21. Although the second latch assembly 50 is unlatched, a portion 3c of the modified lift profile 3b is applied to the late intake valve roller 31. The portion 3c of the modified lift profile 3b that is applied to the late intake valve roller 31 is the portion that exceeds the maximum lost motion stroke LMMAX.

[0041] In particular, as the first and second cams 22, 32 rotate, the main rocker body 11 rotates according to the main intake lift profile 2a of the first cam 22. As the second cam 32 approaches the portion 3c of the modified lift profile 3b that is in excess of the maximum lost motion stroke LMMAX, the portion 3c causes the second lost motion spring 17 to be compressed such that no motion is transferred to the main rocker body 11. As illustrated in FIG. 4, an entire of the portion 3c is less than the main intake lift profile 2a and occurs during the main intake lift profile 2a so that no motion from the portion 3c is applied to the main rocker body 11.

[0042] Referring to FIG. 5, when both the first latch assembly 40 and the second latch assembly 50 are latched, both the main intake lift profile 2a and the modified lift profile 3b are applied to the main rocker body 11. This mode of operation is referred to as modified late intake valve closing (LIVC) because the closing of the intake valve is delayed according to the modified lift profile 3b. This is because the modified lift profile 3b matchesor exceeds the main intake lift profile 2a at all instances.

[0043] The behavior of the system in a standard mode (FIG. 4) and an LIVC mode (FIG. 5) resembles a “normal” LIVC system with the exception that the shape of the LIVC lift is slightly different. As illustrated in FIG. 5, the first latch assembly 40 and the second latch assembly 50 are both latched during the LIVC mode.

[0044] FIG. 6 illustrates the main intake lift profile 2a and the modified lift profile 3b in the cylinder deactivation (CDA) mode. In the CDA mode, the first and second latch assemblies 40, 50 are both unlatched. In this condition, the main intake valve roller 21 and the late intake valve roller 31 are uncoupled from the main rocker body 11. As the first and second cams 22, 32 rotate, the portion of the modified lift profile 3b of the second cam 32 that exceeds the maximum lost motion stroke LMMAX (as discussed above) now causes the main rocker body 11 to follow a recharge lift 6 (the recharge lift 6 is identical to the portion 3c discussed in detail above). In other words, the maximum lost motion stroke LMMAX of the second lost motion assembly 30 is exceeded when the second cam 32 reaches the portion 3c of its profile that exceeds the maximum lost motion stroke LMMAX. Once this is exceeded, the recharge lift 6 will be applied to the main rocker body 11 thereby causing the valve (not shown) to open. This small lift, i.e., the recharge lift 6, results in a constant recharge function wherein the valve (not shown) associated with the rocker arm assembly 10 is periodically opened during the CDA mode.

[0045] FIG. 7 illustrates an alternative LIVC mode wherein the first latch assembly 40 is unlatched and the second latch assembly 50 is latched such that the main intake lift profile 2a inactive and the modified lift profile 3b is active . In other words, the late intake valve roller 31 is coupled to the main rocker body 11 while the main intake valve roller 21 is uncoupled such that the motion experienced by the main rocker body 11 is the modified lift profile 3b. This alternative LIVC mode is similar to the LIVC mode discussed with reference to FIG. 5, but requires that only the second latch assembly 50 be in the latched position.

[0046] The rocker assembly according to the present disclosure thereby opens the intake valve momentarily during the CDA mode to allow air to enter the piston chamber.

[0047] While various features are presented above, it should be understood that the features may be used singly or in any combination thereof. Further, it should be understood that variations and modifications may occur to those skilled in the art to which the claimed examples pertain. While the illustrations provide exemplary embodiments, they are not necessarily drawn to scale and can include additional or alternative elements in suitableoperation.

Claims

ClaimsWhat we claim is:

1. A valve train assembly for actuating an intake valve, the valve train assembly comprising: a rocker arm assembly comprising: a main rocker body having a valve end, a first latch assembly configured to selectively couple a main intake valve roller to the main rocker body, the first latch assembly having a latched position wherein the main intake valve roller is coupled to the main rocker body and an unlatched position wherein the main intake valve roller is uncoupled from the main rocker body, a first lost motion assembly configured to bias the main intake valve roller to a first position wherein the first latch assembly is movable between the latched position and the unlatched position, , a second latch assembly configured to selectively couple a late intake valve roller to the main rocker body, the second latch assembly having a latched position wherein the late intake valve roller is coupled to the main rocker body and an unlatched position wherein the late intake valve roller is uncoupled from the main rocker body, and a second lost motion assembly configured to bias the late intake valve roller to a first position wherein the second latch assembly is movable between the latched position and the unlatched position, the second lost motion assembly configured to allow the late intake valve roller to move a predetermined maximum distance relative to the main rocker body when the second latch assembly is in the unlatched position, a first cam configured to engage the main intake valve roller wherein the first cam has a main intake valve lift profile; and a second cam configured to engage the late intake valve roller wherein, when the first latch assembly and the second latch assembly are in the unlatched position and after the late intake valve roller has moved the predetermined maximum distance, a portion of a late intake valve lift profile of the second cam applies additional motion tothe late intake valve roller such that the late intake valve roller and the main rocker body are coupled together and move as a unitary body.

2. The valve train assembly of claim 1 , wherein a maximum lift of the late intake valve lift profile exceeds a maximum lift of the main intake valve lift profile by a predetermined height.

3. The valve train assembly of claim 1, wherein a first lost motion spring of the first lost motion assembly is secured to the main rocker body at one end and to a bracket holding the main intake valve roller at a second end, and a second lost motion spring of the second lost motion assembly is secured to the main rocker body at one end and to a bracket holding the late intake valve roller at a second end.

4. The valve train assembly of claim 3, wherein when the first latch assembly and the second latch assembly are unlatched, a lift of the second cam compresses the second lost motion spring.

5. The valve train assembly of claim 1, wherein during a cylinder deactivation mode the first latch assembly and the second latch assembly are in the unlatched positions.

6. The valve train assembly of claim 1, wherein when the first latch assembly is in the latched position the main intake valve roller and the main rocker body pivot as a unitary body.

7. The valve train assembly of claim 1 , wherein when the second latch assembly is in the latched position the late intake valve roller and the main rocker body pivot as a unitary body.

8. The valve train assembly of claim 1, wherein during a late intake valve closing mode, the first latch assembly and the second latch assembly are in the latched positions.

9. The valve train assembly of claim 1, wherein when both the first latch assembly and the second latch assembly are in the latched position, a displacement applied to the valve end of the main rocker body is a greater of the main intake valve lift profile and the late intake valve lift profile.

10. A valve train assembly for actuating an intake valve, the valve train assembly comprising: a rocker arm assembly comprising: a main rocker body, a latch assembly configured to selectively couple a late intake valve roller to the main rocker body, the latch assembly having a latched position wherein the late intake valve roller is coupled to the main rocker body and an unlatched position wherein the late intake valve roller is uncoupled from the main rocker body, and a lost motion assembly configured to bias the late intake valve roller to a first position wherein the latch assembly is movable between the latched position and the unlatched position, the lost motion assembly configured to allow the late intake valve roller to move a predetermined maximum distance when the latch assembly is in the unlatched position, and a cam configured to engage the late intake valve roller, wherein, when the latch assembly is in the unlatched position and after the late intake valve roller has moved the predetermined maximum distance, a portion of a late intake valve lift profile of the cam applies additional motion to the late intake valve roller such that the late intake valve roller and the main rocker body are coupled together and move as a unitary body.

11. The valve train assembly according to claim 10, the rocker arm assembly further comprising: a second latch assembly configured to selectively couple a main intake valve roller to the main rocker body, the second latch assembly having a latched positionwherein the main intake valve roller is coupled to the main rocker body and an unlatched position wherein the main intake valve roller is uncoupled from the main rocker body, a second lost motion assembly configured to bias the main intake valve roller to a first position wherein the second latch assembly is movable between the latched position and the unlatched position; and a second cam configured to engage the main intake valve roller wherein the second cam has a main intake valve lift profile.

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