Exhaust valve stop to operate split exhaust supercharging system
By independently controlling the activation and deactivation of the scavenging exhaust valve and pressure relief exhaust valve, the problem of insufficient boost pressure of the turbocharger under the peak engine load is solved, the exhaust gas temperature and engine efficiency are improved, and the benefits of split exhaust gas boost are expanded.
Patent Information
- Application Number
- CN202380082156.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Priority Date
- 2022-11-28
- Filing Date
- 2023-11-27
- Publication Date
- 2025-07-08
AI Technical Summary
In traditional shunt exhaust boosting systems, the turbocharger cannot provide all boosting pressure under the peak engine load, and the exhaust gas temperature has an adverse impact on performance.
The exhaust system of multiple cylinders is adopted, including a scavenging exhaust valve and a pressure relief exhaust valve. The activation and deactivation of the valve are independently controlled through the camshaft and oil valve system to achieve the diversion exhaust pressure of the exhaust gas.
It increases the exhaust gas temperature, enhances the engine emission and efficiency, expands the benefits of diversion exhaust pressure, and reduces the problem of low flow efficiency.
Smart Images
Figure CN120283102A_ABST
Abstract
Description
Background Art
[0001] As is well known, a split-flow exhaust boosting system can be used to reduce internal residual pumping and improve the catalyst light-off of a turbocharged spark ignition engine. However, in such a setup, since part of the exhaust gas energy is lost to the turbine, the turbocharger typically cannot provide the full boost pressure at the engine peak load.
[0002] Traditional solutions to this problem include using two external valves. In such a system, a blow-off valve is installed in the line of a blow-off path connected to the turbine inlet. A scavenge valve is installed in the line of a scavenge path connected to the inlet of a catalytic converter downstream of the turbine. These two valves are typically on-off valves. However, this arrangement still places limitations on the exhaust gas temperature, thus having an adverse effect on performance. Summary of the Invention
[0003] The Summary of the Invention is provided to introduce a series of concepts that will be further described in the following Detailed Description. The Summary of the Invention is not intended to identify key or essential features of the claimed subject matter, nor is it intended to be used to help limit the scope of the claimed subject matter.
[0004] In one aspect, embodiments disclosed in this specification relate to an exhaust system including a plurality of cylinders. Each cylinder includes a scavenge exhaust valve and a blowdown exhaust valve. The exhaust system further includes means for enabling and disabling the scavenge exhaust valve and the blowdown exhaust valve. Additionally, the exhaust system includes a scavenge path leading from the scavenge exhaust valve and a blowdown path leading from the blowdown exhaust valve. Furthermore, the exhaust system includes a camshaft that includes a plurality of scavenge cams and a plurality of blowdown cams. During rotation of the camshaft, when the scavenge exhaust valve is enabled, the scavenge cam interacts with the scavenge exhaust valve to open and close the scavenge exhaust valve. Additionally, during rotation of the camshaft, when the blowdown exhaust valve is enabled, at a time different from the opening and closing of the scavenge exhaust valve, the blowdown cam interacts with the blowdown exhaust valve to open and close the blowdown exhaust valve.
[0005] In one aspect, embodiments disclosed in this specification relate to a method that includes providing a plurality of cylinders in an engine, each cylinder including a scavenge exhaust valve and a blowdown exhaust valve. The scavenge exhaust valve and the blowdown exhaust valve are actuated, and a camshaft including a plurality of scavenge cams and a plurality of blowdown cams is rotated. During rotation of the camshaft, the scavenge cams interact with the scavenge exhaust valve to open and close the scavenge exhaust valve. Additionally, during rotation of the camshaft, at a time different from the opening and closing of the scavenge exhaust valve, the blowdown cams interact with the blowdown exhaust valve to open and close the blowdown exhaust valve.
[0006] Other aspects and advantages of the claimed subject matter will become apparent from the following description and the appended claims. BRIEF DESCRIPTION OF THE DRAWINGS
[0007] Specific embodiments of the disclosed technology will now be described in detail with reference to the drawings. For consistency, like elements in the various drawings are denoted by like reference numerals.
[0008] Figure 1 An overall exhaust system 102 is schematically illustrated in accordance with one or more embodiments.
[0009] Figure 2 A switchable finger follower system is schematically illustrated in accordance with one or more embodiments.
[0010] Figures 3A to 3D Components of a finger follower 344 for a scavenge exhaust valve and in different drive phases are schematically illustrated in accordance with one or more embodiments.
[0011] Figure 4 The effects of different cam profiles on a scavenge exhaust valve and a blowdown exhaust valve are graphically illustrated in accordance with one or more embodiments.
[0012] Figure 5 A flowchart of a method in accordance with one or more embodiments is provided. DETAILED DESCRIPTION
[0013] In the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the present disclosure. However, it will be apparent to one of ordinary skill in the art that the present disclosure may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.
[0014] Throughout the application, ordinal numbers (e.g., first, second, third, etc.) may be used as adjectives for elements (i.e., any nouns in the application). Unless explicitly stated, e.g., by using terms such as "before", "after", "single", and other such terms, the use of ordinal numbers does not imply or create any particular order of the elements, nor does it limit any element to a single element only. Instead, the use of ordinal numbers is for differentiating between elements. As an example, a first element is different from a second element, and the first element may contain more than one element and may come after (or before) the second element in the ordering of the elements.
[0015] According to one or more embodiments, it is widely contemplated herein to use the exhaust valves present on the engine cylinder head to control the flow of exhaust gases to a split exhaust system. Then, considering the exhaust valve design specifications involved, this allows for an increase in the exhaust gas temperature and an improvement in the flow efficiency in and out of the exhaust ports. As a result, the benefits of split exhaust boosting to engine emissions and efficiency are amplified or multiplied.
[0016] According to one or more embodiments, it is also widely contemplated herein to control the exhaust in a manner that achieves the desired flow direction required for a split exhaust boosting system. To this end, a two-step switchable exhaust valve deactivation device can be used to independently open and close each exhaust valve on the cylinder. Such a deactivation system can be implemented by a cam system that includes cams acting on followers associated with different exhaust valves, and such a deactivation system can be implemented in a manner that supplies oil to the valves in a way that enables independent control of each exhaust valve.
[0017] The present disclosure now turns to working examples of a split exhaust system and associated components according to one or more embodiments, as described and illustrated with reference to Figures 1 to 5 It should be understood and appreciated that these are merely illustrative examples, and within the scope of the embodiments widely contemplated herein, numerous possible implementations can be envisioned.
[0018] Additionally, for ease of reference during the description Figures 1 to 5 the reference numerals may be incremented in multiples of 100 to indicate Figures 1 to 5 similar or like components or elements in
[0019] Figure 1Schematically shown is an overall exhaust system 102 according to one or more embodiments. The engine 104 includes a plurality of cylinders 106; four cylinders are shown in the illustrated example. Each cylinder 106 includes a pair of intake valves 108 and a pair of exhaust valves 110. The intake camshaft 112 includes cams for opening and closing the intake valves 108, and in a manner to be described more fully below, the exhaust camshaft 114 includes cams for opening and closing the exhaust valves 110. The intake camshaft 112 and its cams can be configured in any manner considered suitable or advantageous. By way of an illustrative example, in the case of the exhaust valve configuration discussed in this specification, the intake valve / exhaust valve size ratio can be slightly less than that of a conventional system.
[0020] According to one or more embodiments, one exhaust valve 110 of each cylinder 106 is referred to as a scavenge exhaust valve 110a ( Figure 1 towards the left side of each cylinder as shown), and the other exhaust valve 110 of each cylinder 106 is referred to as a "blowdown exhaust valve" 110b ( Figure 1 towards the right side of each cylinder as shown). At the same time, the exhaust system 102 is a split exhaust system, where the blowdown path leads to the turbine 116 of the turbocharger, and the scavenge path leads directly to the catalytic converter 118 while bypassing the turbine 116. Thus, in the illustrated example, the scavenge path leads from each scavenge exhaust valve 110a via the scavenge manifold 111 and the pipe 113 directly to the pipe 115, which leads to the catalytic converter 118. Additionally, the blowdown path leads from each blowdown exhaust valve 110b via the blowdown manifold 117 and the pipe 119 to the turbine 116. Then, the turbine 116 is connected to the catalytic converter 118 via the pipe 115.
[0021] According to one or more embodiments, mounted on the exhaust camshaft 114 are a plurality of scavenge cams 120 and blowdown cams 122. In a manner to be described more fully below, when the exhaust camshaft 114 rotates, the scavenge cams 120 are configured to drive the opening and closing of the scavenge exhaust valves 110a. During the same rotation of the exhaust camshaft 114, the exhaust cams 122 are configured to drive the opening and closing of the blowdown exhaust valves 110b at a timing that can be different from that of the opening and closing of the scavenge exhaust valves 110a.
[0022] According to one or more embodiments, the oil pipe 124 is fed into the engine 104 in the general direction indicated by 126. Then, the pipe 124 divides into two separate channels (or pipes), namely the first channel 126 and the second channel 128. The first channel 126 is fed into each scavenging exhaust valve 110a and the flow into the first channel 126 is controlled and permitted by the first oil valve 130. The second channel 128 is fed into each pressure relief exhaust valve and the flow into the second channel 128 is controlled and permitted by the second oil valve 132. A suitable control unit 134 may be provided to control and drive the opening and closing of the oil valves 130, 132. Generally speaking, in a manner that will be more fully understood below, the oil pipe 124, the channel 126, the channel 128, the oil valve 130, the oil valve 132 and the control unit 134 may be considered as components of a device for enabling and disabling the scavenging exhaust valve 110a and the pressure relief exhaust valve 110b. Among other things, it should be understood that:
[0023] - The scavenging exhaust valve 110a is enabled in response to the closing of the first oil valve 130 and the reduction of the oil pressure in the first oil channel 126;
[0024] - The scavenging exhaust valve 110a is disabled in response to the opening of the first oil valve 130 and the increase of the oil pressure in the first oil channel 126;
[0025] - The pressure relief exhaust valve 110b is enabled in response to the closing of the second oil valve 132 and the reduction of the oil pressure in the second oil channel 128; and
[0026] - The pressure relief exhaust valve 110b is disabled in response to the opening of the second oil valve 132 and the increase of the oil pressure in the second oil channel 128.
[0027] According to one or more embodiments, in order to drive the oil valves 130, 132, the control unit 134 may suitably adopt any one of a variety of possible forms. For example, the oil valves 130, 132 may be configured as solenoid valves or piezoelectric valves having a known on / off function, and the control unit 134 may be configured to send signals to drive the valves 130, 132. Additionally, although the oil valves 130, 132 are shown and described in this specification for controlling the enabling and disabling of the exhaust valve 110, the exhaust valve 110 may also be enabled / disabled by another similarly acting system (such as an electric, pneumatic or piezoelectric system).
[0028] According to one or more embodiments, when the first oil valve 130 is closed, the oil pressure in the first passage 126 is relatively low and at a first oil pressure level. In response to this lower oil pressure, the components of each scavenge exhaust valve 110a can be driven in a manner to deactivate the valve 110a such that the valve 110a remains closed. Further, when the first oil valve 130 is open, the oil pressure in the first passage 126 is relatively high and at a second oil pressure level greater than the first oil pressure level. In response to this higher oil pressure, the said components of each scavenge exhaust valve 110a can be driven in a manner to activate the valve 110a such that the valve 110a can open and close during normal operation.
[0029] Similarly, according to one or more embodiments, when the second oil valve 132 is closed, the oil pressure in the second passage 126 is relatively low and at a first oil pressure level. In response to this lower oil pressure, the components of each blow-off exhaust valve 110b can be driven in a manner to deactivate the valve 110a such that the valve 110b remains closed. Further, when the second oil valve 132 is open, the oil pressure in the second passage 128 is relatively high and at a second oil pressure level greater than the first oil pressure level. In response to this higher oil pressure, the said components of each blow-off exhaust valve 110b can be driven in a manner to activate the valve 110b such that the valve 110b can open and close during normal operation.
[0030] Generally speaking, according to one or more embodiments, the oil pressure at the scavenge exhaust valve 110a and the blow-off exhaust valve 110b can be directly related to the manner of deactivating these valves. However, according to this working example, the range can be from about 2 bar of the above-mentioned lower oil pressure to about 4 bar of the above-mentioned higher oil pressure.
[0031] In addition, according to one or more embodiments, the oil valve control unit 134 can be configured to control the oil valves 130 and 132 relative to each other in a manner to achieve a predetermined pattern or protocol for the scavenge exhaust valve 110a and the blow-off exhaust valve 110b to open and close relative to each other. In other words, the oil valve control unit 134 can be used to control the oil valves 130 and 132 to achieve different protocols for activating and deactivating the scavenge exhaust valve 110a and the blow-off exhaust valve 110b in any manner considered appropriate or advantageous.
[0032] Figure 2 Schematically shown is a switchable finger follower system according to one or more embodiments, which can be used with Figure 1 the system 102 shown therein. It can continue to be referred to jointly with Figure 1 and Figure 2 .
[0033] According to one or more embodiments, Figure 2The camshaft 114 on which the scavenging cam 120 and the pressure relief cam 122 are mounted is shown. When viewed along the axial direction with respect to the shaft 114, the scavenging cam 120 includes a first "closing" lobe 138, an "opening" lobe 136, and a second "closing" lobe 138. Similarly, when viewed along the axial direction with respect to the shaft 114, the scavenging cam includes a first "closing" lobe 142, an "opening" lobe 140, and a "closing" lobe 142. Generally, the opening lobes 136, 140 of the cam can be understood to include cam profiles that engage with a movable member (e.g., one or more portions of the switchable finger follower 144, 152 described in this specification) during rotation of the shaft 114 to cause the movable member to move periodically. On the other hand, the closing lobes 138, 142 of the cam can be understood not to include cam profiles that can achieve the movement of the aforementioned movable member.
[0034] According to one or more embodiments, although two closing lobes 138 are shown for the scavenging cam 120 and two closing lobes 142 are shown for the pressure relief cam 122, it should be understood that this configuration is presented only by way of example and non-limiting example. As an alternative, only one closing lobe 138 for the scavenging cam 120 and one closing lobe 142 for the pressure relief cam 122 may be included. In yet another alternative embodiment, two opening lobes 136 axially arranged on both sides of a single closing lobe 138 may be included for the scavenging cam 120, and two opening lobes 140 axially arranged on both sides of a single closing lobe 142 may be included for the pressure relief cam 122.
[0035] According to one or more embodiments, it is also shown in Figure 2 the components of the scavenging exhaust valve 110a and the pressure relief exhaust valve 110b on one of the cylinders 106. The scavenging exhaust valve 110a may include a switchable finger follower 144 mounted for pivotal movement about a pivot 146. The first end of the finger follower 144 may engage a valve stem 148 on which a spring is mounted. The oil supply 150 may lead from a first oil passage 126 to a chamber or container integrated with the finger follower 144.
[0036] According to one or more embodiments, the pressure relief exhaust valve 110b may be configured similarly. Thus, the pressure relief exhaust valve 110b may include a switchable finger follower 152 mounted for pivotal movement about a pivot 154. The first end of the finger follower 152 may engage a valve stem 156 on which a spring is mounted. The oil supply 158 may lead from a second oil passage 128 to a chamber or container integrated with the finger follower 152.
[0037] According to one or more embodiments, any of a variety of possible implementations may be employed for finger followers 144 and 152. For example, the appropriate mechanism for a switchable finger follower may be understood from, e.g., the article by Zurface, A., Brownell, S., Genise, D., Tow, P., et al. (“Design and Development of a Switching Roller Finger Follower for Discrete Variable Valve Lift in Gasoline Engine Applications,” SAE Int. J. Fuels Lubr. 5(3):2012, doi:10.4271 / 2012-01-1639).
[0038] Figures 3A to 3D Components of a finger follower 344 for a scavenging exhaust valve and in different driving stages according to one or more embodiments are schematically shown. It should be understood that Figures 3A to 3D the example shown is for illustrative purposes only and depicts possible driving modes at a very general level. Thus, Figures 3A to 3D the finger follower 344 and its associated principles shown in Figure 1 and Figure 2 can be used in conjunction with the arrangements shown in
[0039] Figure 3A A finger follower 344 in a first configuration according to one or more embodiments is shown. Generally, the finger follower 344 may include an auxiliary movable portion 356 that may be independently driven or moved relative to the body 358 of the finger follower 344. To enable independent driving or movement, the finger follower 344 may also include a slidable latch or pin 360 that is moved by an oil supply 350 and its associated oil pressure. As such, the oil supply 350 may be in communication with a first oil passage, such as that shown at 126 in Figure 1 . Thus, when the oil pressure in the oil supply 350 is relatively low, the latch or pin 360 may be in an initial “latched,” “extended,” or “locked” position as shown to hold the auxiliary movable portion 356 in place so that it does not move independently relative to the body 358 of the finger follower 344. For example, the latch or pin 360 may be received in a compatible slot or receptacle 362 in the auxiliary movable portion 356.
[0040] According to one or more embodiments, a scavenging cam 320 is also schematically shown in Figure 3A that may be associated with reference to Figure 1 and Figure 2The scavenging cam 120 described and shown is similarly configured. Thus, the opening lobe 336 and the closing lobe 338 are also shown in Figure 3A . Here, the leading end of the opening lobe 336 is shown in the "9 o'clock" position, at which time it has not engaged any part of the finger follower 344.
[0041] Figure 3B The finger follower 344 in a second configuration according to one or more embodiments is shown. Here, the leading end of the opening lobe 336 is shown in the "12 o'clock" position, where the opening lobe 336 engages the surface of the finger follower 344 (e.g., on the second movable part 356 itself), causing the entire finger follower 344 to pivot about the pivot 346 and move the valve stem 348. Then, the continued rotation of the cam 320 causes the valve stem 348 to reciprocate and thus effectively actuates the valve (e.g., Figure 1 the scavenging exhaust valve 110a shown) by opening and closing the valve.
[0042] Figure 3C The finger follower 344 in a third configuration according to one or more embodiments is shown. Thus, when the oil pressure in the oiler 350 is relatively high, the latch or pin 360 can eventually be in the "retracted", "unlatched", or "unlocked" position to allow the auxiliary movable part 356 to move independently relative to the rest of the finger follower 144. Here, the leading end of the opening lobe 336 is again shown in the "9 o'clock" position, at which time it has not engaged any part of the finger follower 344.
[0043] Figure 3D The finger follower 344 in a fourth configuration according to one or more embodiments is shown. Here, the leading end of the opening lobe 336 is shown in the "12 o'clock" position, where the opening lobe 336 engages the surface on the auxiliary movable part 356. As a result, the auxiliary movable part 356 moves to neutralize the physical effect of the opening lobe 336. Since there is no cam profile associated with the closing lobe 338 of the cam, the cam 320 does not contact any other part of the finger follower 344 (e.g., the body 358). Thus, the finger follower 344 does not actually displace about the pivot 346, and thus keeps the valve stem 348 stationary and effectively deactivates the associated valve (e.g., Figure 1 the scavenging exhaust valve 110a shown).
[0044] According to one or more embodiments, although the auxiliary movable part 356 is shown very schematically as being displaced in a sliding manner relative to the body 358, it should be understood that other types of independent displacement of the auxiliary movable part 356 are also possible. For example, the auxiliary movable part 356 can be pivotally mounted on the body 358 and can pivot in response to the engagement of the opening lobe 336 of the cam while the body 358 remains stationary.
[0045] According to one or more embodiments, it should be understood that although it has been described relative to Figures 3A to 3D the finger follower 344 for the scavenging exhaust valve, similar features and functions can be similarly applied to the finger follower of the pressure relief exhaust valve and are applied in cases such as the arrangements shown in Figure 1 and Figure 2 In addition, although the switchable finger follower has been discussed above, it should be understood that a wide variety of alternatives can be envisioned that will function similarly and provide similar effects. For example, arrangements such as a switchable pivot element system, a sliding cam system, or an electrohydraulic valve train system can be used without departing from the scope disclosed in this specification.
[0046] Figure 4 The effects of different cam profiles on the scavenging exhaust valve and the pressure relief exhaust valve according to one or more embodiments are graphically illustrated by way of exemplary and non-limiting working examples. Thus, Figure 4 the figures in
[0047] plot the valve lift against the crank timing. Figure 1 and Figure 2 According to one or more embodiments and with reference to the examples shown in Figure 4 the valve lift can correspond to the displacement of the valve stems 148, 156, and the crank timing can correspond to the rotational displacement of the camshaft 114 relative to TDC (top dead center). As shown, the vertical data lines in
[0048] Figure 5 A flowchart of a method according to one or more embodiments is provided. Specifically, Figure 5 a method of operating an exhaust system is described. Figure 5 One or more of the blocks in Figures 1 to 4 can be performed using one or more components as described in Figure 5 . Although the individual blocks in Figure 5 are presented and described in sequence, those skilled in the art will understand that some or all of these blocks can be performed in a different order, can be combined or omitted, and some or all of these blocks can be performed in parallel. In addition, these blocks can be performed actively or passively.
[0049] First, according to one or more embodiments, a plurality of cylinders are provided in an engine, each cylinder including a scavenge exhaust valve and a blow-off exhaust valve (step 570). This can correspond to Figure 1 the engine 104, the cylinder 106, and the scavenge exhaust valve 110a and the blow-off exhaust valve 110b shown in Figure 1 . The scavenge exhaust valve and the blow-off exhaust valve can be enabled (step 572). This can correspond to supplying oil to the scavenge exhaust valve 110a and the blow-off exhaust valve 110b via oil passages 126 and 128, respectively, as described and shown herein. The camshaft including a plurality of scavenge cams and a plurality of blow-off cams can be rotated (step 574). This can correspond to the rotation of the camshaft 114 and the scavenge cam 120 and the blow-off cam 122, as described and shown with reference to Figure 1 and Figure 2 .
[0050] According to one or more embodiments, during the rotation of the camshaft, the scavenge cam can interact with the scavenge exhaust valve to open and close the scavenge exhaust valve (step 576). Additionally, during the rotation of the camshaft, at a time different from the opening and closing of the scavenge exhaust valve, the blow-off cam can interact with the blow-off exhaust valve to open and close the blow-off exhaust valve (step 578). This can correspond to the opening and closing of the scavenge exhaust valve and the blow-off exhaust valves 110a, 110b via the scavenge cam 120 and the blow-off cam 122, as described and shown with reference to Figure 1 and Figure 2 . This can also be understood by way of an exemplary and non-limiting example with reference to the figures described and shown with respect to Figure 4 .
[0051] Rather than using two external valves (i.e., an exhaust valve and a scavenge valve) to control the path of the exhaust gas flow, the embodiments disclosed in this specification use the exhaust valves originally on the engine to control the exhaust gas flow for split-flow exhaust boosting. In addition, these exhaust valves are by Figure 4Process control is thus enabled, such that they can achieve the flow directions required for a split-flow exhaust turbocharging system. The exhaust valves, which were originally on the engine cylinder head, are used to control the flow of exhaust gases to the split-flow exhaust system. This not only increases the exhaust gas temperature limit resulting from the exhaust valve design specifications, but also reduces the flow inefficiencies in and out of the exhaust ports, in order to extend the benefits of split-flow exhaust turbocharging to engine emissions and efficiency.
[0052] In view of the foregoing, it should be understood that, according to one or more embodiments, an advantage is obtained by effectively increasing the exhaust gas temperature limit, as compared to the previously mentioned conventional arrangements. In particular, this is achieved by the exhaust valve design specifications and by significantly increasing the flow efficiency through the use of the exhaust ports on the engine. This enhances the general benefits associated with split-flow exhaust turbocharging related to engine emissions and efficiency.
[0053] Although only a few exemplary embodiments have been described in detail above, those skilled in the art will readily appreciate that many modifications may be made to the exemplary embodiments without materially departing from the invention. Accordingly, all such modifications are intended to be included within the scope of the present disclosure as defined by the appended claims. In the claims, a functional limitation (means-plus-function clause) is intended to cover the structures described in the present disclosure as performing the recited function, which covers not only structural equivalents but also equivalent structures. Thus, although a nail and a screw may not be structural equivalents because a nail uses a cylindrical surface to fasten wooden parts together while a screw uses a helical surface, in the context of fastening wooden parts, a nail and a screw may be equivalent structures.
Claims
1. An exhaust system (102), the exhaust system (102) comprising: a plurality of cylinders (106); each cylinder (106) includes a scavenging exhaust valve (110a) and a pressure relief exhaust valve (110b); means for enabling and disabling the scavenging exhaust valve (110a) and the pressure relief exhaust valve (110b); a scavenging path leading from the scavenging exhaust valve (110a); a pressure relief path leading from the pressure relief exhaust valve (110b); and camshafts (112, 114), the camshafts (112, 114) including a plurality of scavenging cams (120) and a plurality of pressure relief cams (122); wherein, during rotation of the camshafts (112, 114): the scavenging cams (120) interact with the scavenging exhaust valve (110a) to open and close the scavenging exhaust valve (110a) when the scavenging exhaust valve (110a) is enabled; and when the pressure relief exhaust valve (110b) is enabled, at a time different from the opening and closing of the scavenging exhaust valve (110a), the pressure relief cams (122) interact with the pressure relief exhaust valve (110b) to open and close the pressure relief exhaust valve (110b).
2. The exhaust system (102) according to claim 1, further comprising: a turbine (116); wherein, the pressure relief path leads from the pressure relief exhaust valve (110b) to the turbine (116).
3. The exhaust system (102) according to claim 2, wherein, The scavenging path bypasses the turbine (116).
4. The exhaust system (102) according to claim 3, further comprising: a catalytic converter (118); wherein, the scavenging path leads from the scavenging exhaust valve (110a) to the catalytic converter (118).
5. The exhaust system (102) according to any one of claims 1 to 4, wherein, The means includes: a first oil passage (126) supplying oil to the scavenging exhaust valve (110a); and a second oil passage (128) supplying oil to the pressure relief exhaust valve (110b).
6. The exhaust system (102) according to claim 5, wherein, The means further includes: an oil pipe (124); a first oil valve (130) allowing the flow of oil from the oil pipe (124) to the first oil passage (126); and a second oil valve (132) allowing the flow of oil from the oil pipe (124) to the second oil passage (128).
7. The exhaust system (102) according to claim 6, wherein: the means further includes a control unit (134); and the control unit (134) controls the opening and closing of each of the first oil valve (130) and the second oil valve (132).
8. The exhaust system (102) according to claim 7, wherein: the scavenging exhaust valve (110a) is enabled in response to the closing of the first oil valve (130) and a decrease in the oil pressure in the first oil passage (126); and the pressure relief exhaust valve (110b) is enabled in response to the closing of the second oil valve (132) and a decrease in the oil pressure in the second oil passage (128).
9. The exhaust system (102) according to claim 8, wherein: the scavenging exhaust valve (110a) is deactivated in response to the opening of the first oil valve (130) and the increase in oil pressure in the first oil passage (126); and the pressure relief exhaust valve (110b) is deactivated in response to the opening of the second oil valve (132) and the increase in oil pressure in the second oil passage (128).
10. The exhaust system (102) according to claim 7, wherein: the scavenging exhaust valve (110a) is deactivated in response to the opening of the first oil valve (130) and the increase in oil pressure in the first oil passage (126); and the pressure relief exhaust valve (110b) is deactivated in response to the opening of the second oil valve (132) and the increase in oil pressure in the second oil passage (128).
11. The exhaust system (102) according to any one of claims 1 to 10, wherein: the scavenging cams (120) each include an opening lobe (136, 140, 336) and one or more closing lobes (138, 142, 338); and the scavenging exhaust valves (110a) each include a movable member (144, 152, 344); wherein the opening lobe (136, 140, 336) includes a cam profile that engages with the movable member (144, 152, 344) to periodically move the movable member (144, 152, 344) and open and close the scavenging exhaust valve (110a); and wherein the one or more closing lobes (138, 142, 338) do not include a cam profile configured to effect movement of the movable member (144, 152, 344).
12. The exhaust system (102) according to claim 11, wherein, The movable member (144, 152, 344) includes a switchable finger follower.
13. The exhaust system (102) according to any one of claims 1 to 12, wherein: the pressure relief cams (122) each include an opening lobe (136, 140, 336) and one or more closing lobes (138, 142, 338); and the pressure relief exhaust valves (110b) each include a movable member (144, 152, 344); wherein the opening lobe (136, 140, 336) includes a cam profile that engages with the movable member (144, 152, 344) of the pressure relief exhaust valve (110b) to periodically move the movable member (144, 152, 344) of the exhaust valve (110b) and open and close the pressure relief exhaust valve (110b); and wherein the one or more closing lobes (138, 142, 338) do not include a cam profile configured to effect movement of the movable member (144, 152, 344) of the pressure relief exhaust valve (110b).
14. The exhaust system (102) according to claim 13, wherein, The movable member (144, 152, 344) of the pressure relief exhaust valve (110b) includes a switchable finger follower.
15. A method, comprising: A plurality of cylinders (106) are provided in an engine (104), and each cylinder (106) includes a scavenging exhaust valve (110a) and a pressure relief exhaust valve (110b); The scavenging exhaust valve (110a) and the pressure relief exhaust valve (110b) are enabled; and The camshafts (112, 114) are rotated, and the camshafts (112, 114) include a plurality of scavenging cams (120) and a plurality of pressure relief cams (122); Wherein, during the rotation of the camshafts (112, 114): The scavenging cams (120) interact with the scavenging exhaust valve (110a) to open and close the scavenging exhaust valve (110a); and At a time different from the opening and closing of the scavenging exhaust valve (110a), the pressure relief cams (122) interact with the pressure relief exhaust valve (110b) to open and close the pressure relief exhaust valve (110b).
16. The method according to claim 15, wherein, Enabling the scavenging exhaust valve (110a) and the pressure relief exhaust valve (110b) includes supplying oil to the scavenging exhaust valve (110a) and the pressure relief exhaust valve (110b).
17. The method according to claim 15 or 16, wherein, The scavenging exhaust valve (110a) and the pressure relief exhaust valve (110b) are enabled independently of each other.
18. The method according to any one of claims 15 to 17, wherein: The scavenging exhaust valve (110a) is enabled by supplying oil to the scavenging exhaust valve (110a) at a first oil pressure level; and The scavenging exhaust valve (110a) is disabled by supplying oil to the scavenging exhaust valve (110a) at a second oil pressure level greater than the first oil pressure level.
19. The method according to any one of claims 15 to 18, wherein: The pressure relief exhaust valve (110b) is enabled by supplying oil to the pressure relief exhaust valve (110b) at a first oil pressure level; And The pressure relief exhaust valve (110b) is disabled by supplying oil to the pressure relief exhaust valve (110b) at a second oil pressure level greater than the first oil pressure level.