EP3411568B1

EP3411568B1 - Variable rocker ratio system for a switchable rocker arm

Info

Publication number: EP3411568B1
Application number: EP17702373.6A
Authority: EP
Inventors: Majo Cecur
Original assignee: Eaton Intelligent Power Ltd
Current assignee: Eaton Intelligent Power Ltd
Priority date: 2016-02-01
Filing date: 2017-01-31
Publication date: 2020-10-21
Anticipated expiration: 2037-01-31
Also published as: EP3411568A1; WO2017134062A1

Description

FIELD

The present disclosure relates generally to internal exhaust gas recirculation and switchable rocker arm assemblies.

BACKGROUND

Switching rocker arms allow for control of valve actuation by alternating between two or more states, usually involving multiple arms, such as in inner arm and outer arm. In some circumstances, these arms engage different cam lobes, such as low-lift lobes, high-lift lobes, and no-lift lobes. Switching rocker arms can be implemented as part of systems commonly referred to as variable valve timing (VVT) or variable valve actuation (VVA) to improve fuel economy, reduce emissions and improve driver comfort over a range of speeds. Mechanisms are required for switching rocker arm modes in a manner suited for operation of internal combustion engines. GB 2 526 552 A (EATON SRL) discloses a valve train assembly has a number of main rocker arms each with a main cam follower and at least one auxiliary cam follower. Each auxiliary cam follower is movably arranged on a rocker arm between a first and second positions. A latch is also used for locking the auxiliary cam follower in the first position. An auxiliary camshaft with a selector cam is provided for each latch to control said latch. EP 0 995 885 A2 (EATON CORP) discloses a rocker arm device for optimizing the functioning of internal combustion engines by controlling the opening and the timing of the cylinder valves according to the engine load and its speed.

SUMMARY

A discrete switchable variable valve lift (VVL) system constructed in accordance to one example of the present disclosure includes a first switchable VVL rocker arm assembly, a second switchable VVL rocker arm assembly and an actuation assembly. The first switchable VVL rocker arm assembly selectively opens a first valve and includes a first outer arm and a first inner arm that are pivotally connected at a pivot axle. A first latch pin moves between a latched position where the first inner arm and first outer arm move together and an unlatched position where the first inner arm rotates relative to the first outer arm. The second switchable VVL rocker arm assembly selectively opens a second valve and includes a second outer arm and a second inner arm that are pivotally connected at a pivot axle. A second latch pin moves between a latched position where the second inner arm and second outer arm move together and an unlatched position where the second inner arm rotates relative to the second outer arm. The actuation assembly includes an actuation shaft rotatably driven by a first motor. The actuation shaft has a first lift cam and a second lift cam. The first and second lift cams selectively move the respective first and second latch pins between the latched and unlatched positions.
The actuation assembly is configured to selectively and alternatively provide four distinct operating conditions. In a first operating condition the first and second latch pins are in the unlatched position. In a second operating condition the first latch pin is in a latched position and the second latch pin is in an unlatched position. The first switchable VVL rocker arm assembly switches to internal exhaust gas recirculation (iEGR), reopening the first engine valve. In a third operating condition the first latch is in an unlatched position and the second latch is in a latched position. The second switchable VVL rocker arm assembly switches to iEGR reopening the second engine valve. In a fourth operating condition the first and second latch pins are both in a latched position. The first and second switchable VVL rocker arm assemblies both switching to iEGR reopening the respective first and second engine valves.
According to additional features, the VVL system further includes a sliding variable rocker ratio system (VRRS) contact arm associated with the first switchable VVL rocker arm assembly. The sliding VRRS contact arm moves relative to an iEGR lobe thereby providing a modulated valve lift. The sliding VRRS contact arm is rotatably coupled to a shaft by way of an eccentric pin. The shaft is driven by a second motor. The first motor is an electric step motor.
According to still other features, the VVL system further comprises three additional first switchable VVL rocker arm assemblies that are configured to move in concert between latched and unlatched positions with the first switchable VVL rocker arm assemblies. Three additional first cams are arranged on the actuation shaft. The respective first cams move the first switchable VVL rocker arm assemblies between the latched and unlatched positions. Three additional second switchable VVL rocker arm assemblies are configured to move in concert between latched and unlatched positions with the second switchable VVL rocker arm assemblies. Three additional second cams are arranged on the actuation shaft. The respective second cams move the second switchable VVL rocker arm assemblies between the latched and unlatched positions. In another configuration the actuation assembly includes a Maltese cross mechanism and an engagement disk. The engagement disk has a locating pin that selectively locates into one of a series of slots defined on the Maltese cross mechanism.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 is a perspective view of a discrete switchable VVL system constructed in accordance to one example of the present disclosure;
Figure 2 is an exploded perspective view of a three-roller VVL rocker arm assembly shown with an exemplary cam;
Figure 3 is a partial sectional view of a latch and lift cam associated with first and second VVL rocker arm assemblies and shown with an associated valve lift profile for a first operating condition;
Figure 4 is a partial sectional view of the latch and lift cam associated with first and second VVL rocker arm assemblies and shown with an associated valve lift profile for a second operating condition;
Figure 3 is a partial sectional view of the latch and lift cam associated with first and second VVL rocker arm assemblies and shown with an associated valve lift profile for a third operating condition;
Figure 3 is a partial sectional view of the latch and lift cam associated with first and second VVL rocker arm assemblies and shown with an associated valve lift profile for a fourth operating condition;
Figure 7A is a side view of a variable rocker ratio system (VRRS) including a VRRS rocker arm assembly having a sliding VRRS contact arm that is actuated by an actuation system according to one example of the present disclosure;
Figure 7B is a side view of the sliding VRRS contact arm of FIG. 7A and shown moving from a first position (solid line) to a second position (phantom line) to achieve variable timing with a fixed event length according to one example of the present disclosure;
Figure 8 is a partial sectional side view of the VRRS rocker arm assembly and cam of FIG. 7A;
Figure 9 is a perspective view of a discrete switchable VVL system having VRRS control and constructed in accordance to one example of the present disclosure
Figure 10 is a partial sectional view of the latch and lift cam associated with first and second VVL rocker arm assemblies of the VVL system of Figure 9 and illustrating modulated (variable) timing with fixed event length;
Figure 11 is an actuation assembly constructed in accordance to additional features of the present disclosure.

DETAILED DESCRIPTION

The present disclosure provides a discrete switchable variable valve lift (VVL) system that allows additional opening of exhaust valves during an intake stroke. In one configuration the exhaust valves can be opened immediately after the main exhaust lift. In another configuration the exhaust valves can additionally or alternatively be opened later in the intake stroke. In another example, the present disclosure additionally provides a variable rocker ratio system (VRRS) that can modulate the timing of the internal exhaust gas recirculation (iEGR) in addition to the discrete switchable VVL system. A mechanism provides for four discrete actuation positions. In one example a Maltese cross configuration is used.
With initial reference to FIG. 1, a discrete switchable VVL system constructed in accordance to one example of the present disclosure is shown and generally identified at reference 10. The discrete switchable VVL system 10 comprises eight three-roller VVL rocker arm assemblies generally identified at reference 20 and individually identified at reference 20a - 20h. The discrete switchable VVL system 10 further includes an actuation assembly 22 having an actuation shaft 24 that rotatably actuates by way of a first motor 30. The first motor 30 can be an electric step motor. The actuation shaft 24 includes four first lift cams collectively identified at 32 and four second lift cams collectively identified at reference 34. The first lift cams 32 are individually identified at reference 32a - 32d. The second lift cams 34 are individually identified at reference 34a - 34d.
The three-roller VVL rocker arm assemblies 20 open and close exhaust valves, collectively identified at reference 40 and individually identified at reference 40a - 40h. Hydraulic lash adjusters (HLA's) collectively identified at reference 44 and individually identified at reference 44a - 44h control lash of a corresponding VVL rocker arm assembly 20a - 20h.
Turning now to FIG. 2, the three-roller VVL rocker arm assembly 20a will be described. It will be appreciated that the other rocker arm assemblies 20b-20h can be constructed similarly. It will further be appreciated that other switchable rocker arm assemblies may be substituted in the discrete switchable VVL system 10 while reaching similar results. The VVL rocker arm assembly 20a includes an outer arm 52 and an inner arm 54 that are pivotally connected at a pivot axle 56. A roller axle 60 extends transversely through the outer arm 52 and supports a pair of outer rollers 66. The inner arm 54 comprises an inner bushing 70 that supports an inner roller 72. The roller axle 60 extends through the inner bushing 70.
The VVL rocker arm assembly 20a includes a latch pin 80 that moves between a latched position and an unlatched position. When the latch pin 80 is in the unlatched position, the inner arm 54 is free to pivot (downward as viewed in FIG. 2) with respect to the outer arm 52 about the pivot axle 56. A biasing member 58 biases the inner arm 54 relative to the outer arm 52 back to the position shown in FIG. 2. When the latch pin 80 is in the latched position, the latch pin 80 engages the inner arm 54 and prevents the inner arm 54 from pivoting with respect to the outer arm 52 such that the inner and outer arms 54 and 52 rotate together about the pivot axle 56 as a single body.
For exemplary purposes, a cam 100 is shown in FIG. 2 for cooperation with the VVL rocker arm assembly 20a. The cam 100 includes an inner cam 102 and a pair of outer cams 104. The inner cam 102 is configured to engage the inner roller 32 while the outer cams 104 are configured to engage the outer rollers 26.
Turning now to FIGS. 3-6, various lift profiles that can be achieved with the discrete switchable VVL system 10 will be described. For clarity, a latch 80e has been identified that is associated with the VVL rocker arm assembly 20e. In this regard operation of the rocker arm pairs 20a and 20e will be described below with the appreciation that the other rocker arm pairs 20b and 20f; 20c and 20g; and 20d and 20h operate similarly. The first motor 30 is configured for electromechanical actuation for rotating the shaft 24 in four distinct positions (corresponding to FIGS. 3-6).
FIG. 3 shows only standard exhaust and intake operating modes with a hot engine and either very low (below 10-15%) or high (above 80-85%) engine load. The exhaust profile is identified at reference 120. The intake profile is identified at reference 122. FIG. 4 shows a standard exhaust profile 130 that is switched to internal exhaust gas recirculation (iEGR), identified at 132 immediately after an exhaust lift. As shown, after completion of standard lift just before closing, the exhaust valve 40e reopens allowing hot exhaust gasses (just expelled) to get back into the cylinder. FIG. 4 is for cold start and cold engine and low load.
FIG. 5 illustrates a standard exhaust profile 140 that is switched to iEGR identified at 142 later (as compared to FIG.4), in the intake stroke. The additional opening of the exhaust valve 40e later in the intake stroke mainly targets NOx reduction. FIG. 5 is low to medium engine speed and load. FIG. 6 illustrates a standard exhaust profile 150 and two distinct switchable iEGR profiles 152, 154 immediately after exhaust lift and/or later in the intake stroke. Both iEGR lift profiles 152, 154 provide additional openings of exhaust valves immediately after the main lift and one later in intake stroke (can be switched on or off). In summary, the discrete switchable VVL system 10 provides four levels of iEGR. None (FIG. 3); a first iEGR 132 (FIG. 4); a second iEGR 142 (FIG. 5); and dual iEGR 152, 154 (FIG. 6).
FIGS. 7A, 7B and 8 illustrate a VRRS rocker arm assembly 210 according to another example of the present disclosure. As will be described herein, the VRRS rocker arm assembly 210 can be used in place of corresponding VVL rocker arm assemblies 20a - 20d to provide a system capable of standard lift, single step iEGR and modulated VRRS timing iEGR. The VRRS rocker arm assembly 210 generally includes a VRRS a switchable VRRS (first arm) 212, a main exhaust lift rocker arm body (second arm) 214, a sliding VRRS contact arm 216 and a latch pin 218. The sliding VRRS contact arm 216 generally includes a pair of sliding VRRS's 220 configured to contact a corresponding pair of iEGR cam lobes 226 of cam 230. A roller 234 rotatably mounted to the main exhaust lift rocker arm body 214 rotatably engages a main exhaust cam lobe 236 of the cam 230.
The latch pin 218 moves between a latched position and an unlatched position. When the latch pin 218 is in the unlatched position, the main exhaust lift rocker arm body 214 is free to pivot relative to the VRRS switchable VRRS 212 about a pivot axis 238. A biasing member 240 biases the main exhaust lift rocker arm body 214 relative to the VRRS switchable VRRS 212 back to the position shown in FIG. 7A. When the latch pin 218 is in the latched position, the latch pin 218 engages the VRRS switchable VRRS 212 and prevents the main exhaust lift rocker arm body 214 from pivoting with respect to the VRRS switchable VRRS 212 such that the main exhaust lift rocker arm body 214 and the VRSS switchable VRRS 212 rotate together about the pivot axis 238 as a single body. An HLA 244 engages the main exhaust lift rocker arm body 214 to minimize lash.
The VRRS rocker arm assembly 210 is part of a VRRS rocker arm system 242 that includes an actuation assembly 248 having a shaft 250 rotatably driven by second motor 260. The second motor 260 can be an electric motor. The shaft 250 connects to the sliding VRRS contact arm 216. The sliding VRRS contact arm 216 is rotatably coupled to a shaft 250 having an eccentric pin 252. While one VRRS rocker arm assembly 210 is shown in FIG. 7A, it will be appreciated that the shaft 250 will have additional eccentric pins configured to engage and move additional VRSS contact arms of corresponding VRSS rocker arm assemblies 210a-210d. For clarity, the shaft 250 and motor 260 have been removed in FIG. 10.
The shaft 250 is caused to rotate by the electric motor 260. Because the pin 252 is eccentric relative to the axis of rotation of the shaft 250, the sliding VRRS contact arm 216 is caused to move generally left and right as viewed in FIG. 7A to achieve early or late opening of the valve (represented by a first position in solid line and a second position in phantom line). In this regard, as the VRRS's 220 can locate at different locations, the pair of iEGR cam lobes 226 engage the VRRS's 220 at different times allowing for variable timing. The VRRS function is only on the sliding VRRS contact arm 216. As a result, cam phasing is attained only on the switchable internal iEGR portion of the VRRS rocker arm assembly 210.
FIG. 9 illustrates a discrete switchable VVL system having VRRS control and constructed in accordance to one example of the present disclosure is shown and generally identified at reference 310. The discrete switchable VVL system having VRRS control 310 is similar to the discrete switchable VVL system 10 described above except that that rocker arm assemblies 20a-20d are replaced with VRSS rocker arm assemblies 210a-210d controlled by the VRSS rocker arm system 242. As shown in FIG. 10, the discrete switchable VVL system 310 allows additional opening of the exhaust valves immediately after the main exhaust lift (identified at iEGR profile 320) and/or modulated timing lift later in the intake stroke. The modulated iEGR profile is identified collectively at reference 330 and individually at 330a, 330b and 330c. It will be appreciated that additional profiles can be attained by moving the sliding VRRS contact arm 216 with the actuation assembly 248.
FIG. 11 illustrates an actuation assembly 350 constructed in accordance to additional features of the present disclosure. The actuation assembly 350 includes a Maltese cross mechanism 352 and an engagement disk 354 that is driven through a drive shaft 358 by an electric motor 360. The Maltese cross mechanism 352 rotates an actuation shaft 370 having a plurality of cams 372. The engagement disk 354 includes a locating pin 380 that selectively locates in slots 382 to rotate the actuation shaft 370 to desired positions. The actuation assembly 350 can be used for discrete positioning, multi-position actuation (such as the four way positioning described above); and multistep actuation of the VRRS rocker arm system 242.

Claims

A discrete switchable variable valve lift, VVL, system (10) comprising:
a first switchable VVL rocker arm assembly (20a) that selectively opens a first valve (40a), the first switchable VVL rocker arm assembly (20a) comprising:
a first outer arm (52) and a first inner arm (54) that are pivotally connected at a pivot axle (56), a first latch pin (80a) that moves between a latched position where the first inner arm (54) and first outer arm (52) move together and an unlatched position where the first inner arm (54) rotates relative to the first outer arm (52);

a second switchable VVL rocker arm assembly (20e) that selectively opens a second valve (40e), the second switchable VVL rocker arm assembly (20e) comprising:
a second outer arm (52) and a second inner arm (54) that are pivotally connected at a pivot axle (56), a second latch pin (80e) that moves between a latched position where the second inner arm (54) and second outer arm (52) move together and an unlatched position where the second inner arm (54) rotates relative to the second outer arm (52); and

an actuation assembly (22) having an actuation shaft (24) rotatably driven by a first motor (30), the actuation shaft (24) having a first lift cam (32) and a second lift cam (34), the first and second cams (32, 34) selectively moving the respective first and second latch pins (80a, 80e) between the latched and unlatched positions wherein the actuation assembly (22) is configured to selectively and alternatively provide four distinct operating conditions including:
a first operating condition wherein the first and second latch pins (80a, 80e) are in the unlatched position;

a second operating condition wherein the first latch pin (80a) is in a latched position and the second latch pin (80e) is in an unlatched position, the first switchable VVL rocker arm assembly (20a) switching to internal exhaust gas recirculation (iEGR), reopening the first engine valve (40a);

a third operating condition wherein the first latch (80a) is in an unlatched position and the second latch (80e) is in a latched position, the second switchable VVL rocker arm assembly (20e) switching to iEGR reopening the second engine valve (40e); and

a fourth operating condition wherein the first and second latch pins (80a, 80e) are in the latched position, the first and second switchable VVL rocker arm assemblies (20a, 20e) both switching to iEGR reopening the respective first and second engine valves (40a, 40e).
The VVL system (10) of claim 1 wherein the first switchable VVL rocker arm assembly (20a) opens iEGR at a first time and the second switchable VVL rocker arm assembly (20e) opens iEGR at a second time, the second time occurring subsequent to the first time.
The VVL system (10) of claim 2, further comprising:
a sliding variable rocker ratio system, VRRS, contact arm (216) associated with the first switchable VVL rocker arm assembly (20a) and that moves relative to an iEGR cam lobe (226) thereby providing a modulated valve lift.
The VVL system (10) of claim 3 wherein the sliding VRRS contact arm (216) is rotatably coupled to a shaft (250) by way of an eccentric pin (252), the shaft (250) driven by a second motor (260).
The VVL system (10) of claim 1 wherein the first motor (30) is an electric step motor.
The VVL system (10) of claim 1, further comprising three additional first switchable VVL rocker arm assemblies (20b, 20c, 20d) that are configured to move in concert between latched and unlatched positions with the first switchable VVL rocker arm assemblies (20a).
The VVL system (10) of claim 6, further comprising three additional first cams (32b, 32c, 32d) arranged on the actuation shaft (24), the respective first cams (32b, 32c, 32d) moving the first switchable VVL rocker arm assemblies (20b, 20c, 20d) between the latched and unlatched positions.
The VVL system (10) of claim 7, further comprising three additional second switchable VVL rocker arm assemblies (20f, 20g, 20h) that are configured to move in concert between latched and unlatched positions with the second switchable VVL rocker arm assemblies (20e).
The VVL system (10) of claim 8, further comprising three additional second cams (34b, 34c, 34d) arranged on the actuation shaft (24), the respective second cams (34b, 34c, 34d) moving the second switchable VVL rocker arm assemblies (20f, 20g, 20h) between the latched and unlatched positions.
The VVL system (10) of claim 1 wherein the actuation assembly includes a Maltese cross mechanism (352) and an engagement disk (354), wherein the engagement disk (354) has a locating pin (380) that selectively locates into one of a series of slots (382) defined on the Maltese cross mechanism (352).
The VVL system (10) of claim 1 further comprising:
a sliding variable rocker ratio system, VRRS, contact arm (216) associated with the first switchable VVL rocker arm assembly (20a) and that moves relative to an iEGR cam lobe (226) thereby providing a variable timing valve lift.
The VVL system (10) of claim 11 wherein the sliding VRRS contact arm (216) is rotatably coupled to a shaft (250) by way of an eccentric pin (252), the shaft (250) driven by a second motor (260).
The VVL system (10) of claim 12 wherein the first switchable VVL rocker arm assembly (20a) opens iEGR at a first time and the second switchable VVL rocker arm (20e) assembly opens iEGR at a second time, the second time occurring subsequent to the first time.
The VVL system (10) of claim 13, further comprising three additional first switchable VVL rocker arm assemblies (20b, 20c, 20d) that are configured to move in concert between latched and unlatched positions with the first switchable VVL rocker arm assemblies (20a); and further comprising three additional first cams (32b, 32c, 32d) arranged on the actuation shaft (24), the respective first cams (32b, 32c, 32d) moving the first switchable VVL rocker arm assemblies (20b, 20c, 20d) between the latched and unlatched positions; and further comprising three additional sliding VRRS contact arms (216) associated with the respective first switchable VVL rocker arm assemblies (20b, 20c, 20d) and that move relative to an iEGR cam lobe (226) thereby providing a variable timing valve lift.
The VVL system (10) of claim 11 wherein the first motor (30) is an electric step motor.