Heavy-duty engines with cylinders that can switch between single-valve and dual-valve actuation

Abstract

The present invention relates to the field of piston internal combustion engines. A heavy-duty engine with cylinders switchable between single-valve and dual-valve actuation is provided. By providing a cam member with a unique cam profile and combining the cam member with a control assembly, a continuously variable hydraulic valvetrain can be switched between single-valve and dual-valve actuation. Furthermore, by providing a control assembly comprising multiple valve members located in different positions, dual-valve exhaust main lift or cylinder deactivation, as well as single-valve compression release braking and early exhaust valve opening and closing, are further implemented.

Description

Technical Field

[0001] The present invention relates to the field of piston internal combustion engines, in particular to a heavy-duty engine in which cylinders can be switched between single-valve drive and double-valve drive. Background Art

[0002] At present, the exhaust valve mechanism used in most mainstream heavy-duty engines is single overhead cam SOHC (there is only one camshaft above the valve to drive the intake and exhaust valves), and the exhaust valve is driven by a rocker arm.

[0003] Heavy-duty engines (internal combustion engines) may include a compression release function to provide auxiliary braking power for the vehicle. This function opens the exhaust valve before the piston reaches top dead center (TDC), allowing gas to be released at a pressure within the cylinder (e.g., above 30 barA). During this compression release process, the reciprocating piston performs negative work, thereby generating braking torque.

[0004] In recent years, a key area of ​​commercial vehicle engine thermal management that has garnered significant attention is exhaust gas thermal management, specifically the active heating of the NOx reduction catalyst (SCR) during cold start and low-load cycles. Actively reducing raw NOx emissions and actively heating aftertreatment devices are on the roadmaps of many commercial vehicle engine manufacturers, as they prepare for the upcoming Euro 7 (EU7) exhaust emissions regulations.

[0005] As a preheating measure for exhaust catalytic converters, engine manufacturers have explored methods that utilize exhaust gas energy to actively heat the aftertreatment pathway during idle. For example, in dual overhead cam (DOHC) engines, the exhaust cam phasing allows for early opening and closing, directing hotter exhaust gas to the catalyst. Early closing increases the amount of residual combustion gases in the cylinder, thereby helping to raise the average cylinder gas temperature. However, in single overhead cam (HOC) engines without cam phasing, active exhaust pathway heating must be achieved through valve lift switching.

[0006] In view of this, it is indeed necessary to provide an integrated valve mechanism for a heavy-duty engine to solve the above problems. Summary of the Invention

[0007] An object of the present invention is to provide a heavy-duty engine in which cylinders can switch between single-valve actuation and dual-valve actuation. The heavy-duty engine combines a cam member with a control assembly so that a continuously variable hydraulic valve mechanism can switch between single-valve actuation and dual-valve actuation.

[0008] To achieve the above-mentioned purpose of the invention, the present invention provides a heavy-duty engine whose cylinders can switch between single-valve drive and dual-valve drive, which includes a hydraulic circuit and a continuously variable hydraulic valve mechanism. The continuously variable hydraulic valve mechanism is arranged corresponding to each cylinder in the heavy-duty engine and includes: a piston assembly, including a pump unit and a cam member driven and connected to the pump unit; an energy storage assembly; a valve return brake assembly, including a brake unit arranged in pairs, two exhaust units arranged corresponding to the brake units, and a mechanical valve bridge assembly arranged between the brake unit and the exhaust unit; a control assembly, including a first control valve arranged between the energy storage assembly and the piston assembly; a valve return brake ... a second control valve at one end of the component and a third control valve arranged between the hydraulic circuit and the continuously variable hydraulic valve mechanism; the mechanical valve bridge component includes a single-valve piston connected to any one of the brake units and a mechanical valve bridge connected to the other brake unit, and the third control valve can control the second control valve to transmit the movement of the cam component to the single-valve piston, thereby driving only the valve stem of one exhaust unit, so that the corresponding cylinder works in a single-valve drive mode; the third control valve can also control the second control valve to transmit the movement of the cam component to the mechanical valve bridge, thereby driving the valve stems of two exhaust units, so that the corresponding cylinder works in a dual-valve drive mode.

[0009] Optionally, the pump unit includes a pump roller connected to the cam member, a pump piston connected to one end of the pump roller, a pump oil chamber for accommodating the pump piston, and a pump spring sleeved on the outer circumference of the pump piston.

[0010] Optionally, the peripheral edge of the cam member is formed with a first drive protrusion and a second drive protrusion spaced apart, the first drive protrusion having three consecutive ramp-up steps and one ramp-down step, the three ramp-up steps and the one ramp-down step covering a total crank angle of 470 degrees.

[0011] Optionally, the second driving protrusion is located between 480 and 600 crank angle degrees on the periphery of the cam member for brake gas recirculation.

[0012] Optionally, the energy storage assembly is connected to the first control valve through an intermediate pressure chamber or a first channel; the energy storage assembly includes an accumulator oil chamber, an accumulator piston movably connected in the accumulator oil chamber, and an accumulator spring sleeved on the outer periphery of the accumulator piston, and the accumulator spring acts on the accumulator piston to tend to make the oil in the accumulator oil chamber flow to the intermediate pressure chamber or the first channel.

[0013] Optionally, the first control valve can control the connection or disconnection between the pump oil chamber and the accumulator oil chamber.

[0014] Optionally, the first control valve is a 2 / 2 normally open solenoid valve; the second control valve is a 3 / 2-way mechanical valve; and the third control valve is a pilot 3 / 2-way solenoid valve.

[0015] Optionally, the brake unit includes a piston unit, the single valve piston is capable of interacting with the piston of the piston unit of one brake unit, the piston of the piston unit of another brake unit is connected to the mechanical valve bridge, and the single valve piston is movably connected to the mechanical valve bridge, so that the single valve piston can move relative to the mechanical valve bridge to drive the valve stem of an exhaust unit to move, and the mechanical valve bridge can drive the valve stems of two exhaust units to move at the same time when it moves.

[0016] Alternatively, the second control valve can, by switching the hydraulic connection state, cause: movement of the cam member to cause oil in the pump oil chamber to enter the piston unit of one brake unit, thereby driving the valve stem of one exhaust unit via the single valve piston, while the mechanical valve bridge remains stationary; or movement of the cam member to cause oil in the pump oil chamber to enter the piston unit of the other brake unit, thereby driving the mechanical valve bridge to move, and the mechanical valve bridge to drive the valve stems of both exhaust units. Advantageous effects of the present invention include: the heavy-duty engine of the present invention combines a cam member with a control assembly, enabling a continuously variable hydraulic valvetrain to switch between single-valve and dual-valve actuation.

[0017] In addition, by providing a control assembly including multiple valve components located in different positions, the exhaust main lift or cylinder deactivation of the dual valves, as well as the compression release braking and early opening and closing of the exhaust valve of the single valve are further achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 The diagram is a schematic structural diagram of a continuously variable hydraulic valve mechanism for a heavy-duty engine according to the present invention.

[0019] Figure 2 yes Figure 1 Schematic diagram of the structure of the cam component.

[0020] Figure 3 It is the lift curve under the exhaust main lift state.

[0021] Figure 4 Schematic diagram of the status of the main exhaust lift continuously variable hydraulic valve mechanism and control components in normal ignition mode.

[0022] Figure 5 The control strategy of the exhaust main lift control component and the cylinder pressure curves under normal ignition mode and main lift.

[0023] Figure 6Schematic diagram of the single valve operating state when the compression release brake CRB1.0 or the early exhaust valve is opened / closed.

[0024] Figure 7 This is the control strategy of the control component in the early valve opening and early valve closing modes and the cylinder pressure curve in the corresponding modes.

[0025] Figure 8 Schematic diagram of the operating status of the control device for stopping valve movement.

[0026] Figure 9 This is the control strategy of the control component in the compression-release brake function mode and the cylinder pressure curve in the corresponding mode. DETAILED DESCRIPTION

[0027] The following describes embodiments of the present invention in detail, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and are not to be construed as limiting the present invention.

[0028] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, "plurality" means two or more, unless otherwise specifically defined.

[0029] In the present invention, unless otherwise expressly specified or limited, the terms "mounted," "connected," "connect," "fixed," etc. should be understood broadly. For example, they may refer to fixed connection, detachable connection, or integration; mechanical connection or electrical connection; direct connection or indirect connection through an intermediate medium; internal communication between two components or interaction between two components. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on specific circumstances.

[0030] In order to make the objectives, technical solutions and advantages of the present invention more clear, the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] The exhaust valvetrains of current mainstream heavy-duty engines typically only provide a single valve lift function. Most heavy-duty engine variable valvetrains switch between different rocker arms. To provide more than two valve lift functions, independent rocker arms are required for switching. The mechanical strength of the switching mechanism plays a decisive role in the valve lift variation. A disadvantage is that the combination of multiple rocker arms or cams takes up valuable engine installation space.

[0032] One challenge with compression release is the cam torque required to open the exhaust valves. Braking force is typically characterized by a peak in cylinder pressure. If both valves are opened at higher cylinder pressures, the torque required to drive the camshaft may be twice as high as if only one valve were open.

[0033] Therefore, if both valves are to be opened simultaneously during compression release, the camshaft material and timing chain must withstand very high torques (e.g. more than 200Nm), or the in-cylinder pressure must be reduced by means of throttling or a turbocharger wastegate.

[0034] If only one exhaust valve needs to be opened, the camshaft torque is reduced, while the cylinder pressure can still be greater than 60 bar A. To switch between single and dual exhaust valves, the single exhaust valve and the movement of the mechanical valve bridge are activated or deactivated hydraulically.

[0035] In fact, researchers discovered that by configuring the cam member's cam profile, compression release braking, exhaust valve main lift, and early opening / closing can be integrated. Furthermore, by calibrating the cam member's rotational trajectory and cutting off the hydraulic pressure between it and the exhaust valve plunger, continuous valve lift variation can be achieved. In other words, the capabilities of the high-speed solenoid valve can be fully utilized to transmit or not transmit the cam trajectory to valve lift.

[0036] In view of this, the present invention provides a heavy-duty engine, which includes a continuously variable hydraulic valve mechanism, and the continuously variable hydraulic valve mechanism is provided corresponding to each cylinder in the heavy-duty engine.

[0037] See also Figure 1 As shown, in this application, the continuously variable hydraulic valve mechanism includes a piston assembly 1, an energy storage assembly 2, a valve return brake assembly 3, and a control assembly 4 for controlling the operation of the piston assembly 1, the energy storage assembly 2, and the valve return brake assembly 3.

[0038] The piston assembly 1 includes a cam member 11 and a pump unit 12 drivingly connected to the cam member 11. Figure 2As shown, the outer peripheral edge of the cam member 11 is formed with a first drive protrusion 111 and a second drive protrusion 112 arranged at intervals. The first drive protrusion 111 has three consecutive ramp-up steps (i.e., the first ramp-up step 1a, the second ramp-up step 1b, the third ramp-up step 1c) and one ramp-down step (1d). The three ramp-up steps and the one ramp-down step (1d) cover a total crank angle CrA of 470 degrees (i.e., equivalent to a cam angle of 0~235°).

[0039] The second driving protrusion 112 is located between the crank angle CrA of 480° and 600° (ie, corresponding to the cam angle of 0° to 60°) on the outer periphery of the cam member 11 for brake gas recirculation BGR and further enhancing the decompression braking power.

[0040] Furthermore, the pump unit 12 includes a pump roller 121 that abuts against the outer peripheral edge of the cam member 11, a pump piston 122 connected to one side of the pump roller 121, a pump oil chamber 123 for accommodating the pump piston 122, and a pump spring 124 sleeved around the outer periphery of the pump piston 122. The pump unit 12 also includes a high-pressure oil chamber or second channel 13 connected to the pump oil chamber 123. The pump spring 124 presses the pump piston 122 toward the cam member 11.

[0041] The accumulator assembly 2 is connected to the control assembly 4 via an intermediate pressure chamber or first passage 21, and is further connected to the piston assembly 1 and the valve return brake assembly 3 through the control assembly 4. The accumulator assembly 2 includes an accumulator oil chamber 22, an accumulator piston 23 movably connected to the accumulator oil chamber 22, and an accumulator spring 24 sleeved around the accumulator piston 23. The intermediate pressure chamber or first passage 21 is connected to the accumulator oil chamber 22, and the accumulator spring 24 acts on the accumulator piston 23, tending to cause the oil in the accumulator oil chamber 22 to flow into the intermediate pressure chamber or first passage 21.

[0042] The valve return brake assembly 3 includes brake units 31, 31' arranged in pairs, exhaust units 32, 32' arranged corresponding to the brake units 31, 31', and a mechanical valve bridge assembly 33 arranged between the brake units 31, 31' and the exhaust units 32, 32'. The exhaust units 32, 32' include exhaust valves and valve stems 321, 321' and exhaust valve springs 322, 322' sleeved on the outer circumference of the valve stems; the exhaust valve springs 322, 322' apply force to the valve stems 321, 321' ( Figure 1 In the middle, the valve stem 321, 321' is pressed upward, so that the valve stem 321, 321' tends to move upward. Here, the exhaust valve spring 322, 322' is only shown schematically. Figure 1In the embodiment, the upper ends of the exhaust valve springs 322 and 322' can act on the lower surfaces of the flanges on the valve stems 321 and 321', and the lower ends of the exhaust valve springs 322 and 322' can be supported by the housing (e.g., the cylinder head or a support portion thereon). Furthermore, the mechanical valve bridge assembly 33 includes a single valve piston 331 connected to one brake unit 31 and a mechanical valve bridge 332 connected to the other brake unit 31.

[0043] The control assembly 4 is a valve assembly used to control the drive and conduction of the piston assembly 1, the energy storage assembly 2, and the valve return brake assembly 3. In the present application, the control assembly 4 includes a first control valve 41 disposed between the energy storage assembly 2 and the piston assembly 1. The first control valve 41 can control the connection or disconnection between the pump oil chamber 123 and the accumulator oil chamber 22. The control assembly 4 also includes a second control valve 42 disposed at one end of the valve return brake assembly 3. Furthermore, the two brake units 31 and 31' are connected to the second control valve 42 via two first hydraulic passages 421 and are switched by the second control valve 42. That is, at the same time, only one of the brake units 31 and 31' can be driven hydraulically.

[0044] The control assembly 4 further includes a third control valve 43 disposed between the hydraulic circuit 5 of the heavy-duty engine and the continuously variable hydraulic valve mechanism; the third control valve 43 is then used to control switching between single-valve actuation and dual-valve actuation of the cylinder.

[0045] It should be noted that in the present application, the hydraulic circuit 5 is connected to the third control valve 43 via a second hydraulic passage 50. The hydraulic circuit 5 includes an oil pump unit 51, a first oil passage 52 for connecting the heavy-duty engine oil pan 6 and the third control valve 43, and a second oil passage 53 for connecting the heavy-duty engine oil pan 6 and the oil pump unit 51. In the present application, the third control valve 43 is a pilot 3 / 2-way solenoid valve, and the third control valve 43 is disposed outside the cylinder head of the cylinder to control the second control valve 42 of each cylinder. Preferably, the first control valve is a 2 / 2 normally open solenoid valve, and the second control valve is a 3 / 2-way mechanical valve.

[0046] The second control valve 42 may be arranged on the exhaust valve of each engine cylinder head, and only one third control valve 43 may be provided. One third control valve 43 may be connected to the second control valve 42 of each engine cylinder head via an oil circuit.

[0047] To facilitate a better understanding of the continuously variable hydraulic valve mechanism for a heavy-duty engine of the present invention, the following description will describe in detail the motion states of various components in the continuously variable hydraulic valve mechanism for a heavy-duty engine during operation.

[0048] See Figure 2 Combined with Figure 3As shown, in a four-stroke internal combustion engine, the first ramp-up step 1a of the first drive protrusion 111 of the cam member 11 covers the first compression release brake of the engine, which starts at 50~60 CrA degrees (crank angle) before TDC ignition and ends at a high point of 3~5 CrA after 0TDC ignition.

[0049] The second ramp-up step 1b of the first drive lobe 111 of the cam member 11 begins at the end of the first ramp-up step 1a, i.e., 3 to 5 CrA after TDC ignition, and continues to 70 CrA after ATDC, and then reaches 90 CrA after ATDC. The second ramp-up step 1b includes early exhaust valve opening in the ignition mode, thereby releasing exhaust gas energy to the post-processing path earlier than in the normal main lift mode.

[0050] The third ramp-up step 1c of the first drive protrusion 111 of the cam member 11 is the longest ramp-up stage, covering the main lift opening sequence. It gradually accelerates from 90 CrA ATDC to 230-235 CrA ATDC.

[0051] The ramp-down step 1d of the first driving protrusion 111 of the cam member 11 is the base circle of the return cam member 11. It starts from the ramp end of the third ramp-up step 1c and ends between 410 and 415 CrA ATDC.

[0052] The fourth ramp-up step of cam member 11 is step 1e of second drive projection 112, which provides brake exhaust gas recirculation (BGR). It begins at 480 CrA ATDC and ends at 600 CrA ATDC. The lift height of the BGR portion should be less than 2 mm to prevent cavitation in the oil flow as cam member 11 returns to base circle during the ramp-down process.

[0053] See also Figure 4 The figure shows the valve bridge operation of the continuously variable hydraulic valve train of the present invention for exhaust main lift in normal ignition mode. In this case, the first control valve 41 is energized, while the third control valve 43 is deenergized. The rising phase of the ramp on the cam member 11 is transmitted to the mechanical valve bridge 332, pushing the two exhaust units 32 and 32' downward, opening the cylinder exhaust passage. The brake unit 31 and the single-valve piston 331 remain stationary in their reference positions. Specifically, the third control valve 43 controls the second control valve 42, transmitting the movement of the cam member 11 to the mechanical valve bridge 332, thereby actuating the valve stems of the two exhaust units, thereby operating the corresponding cylinders in dual-valve actuation mode.

[0054] For further information, see Figure 5 Combined with Figure 2 、 Figure 4As shown, the first control valve 41 is energized briefly after the cam member 11 rotates to the second ramp-up step 1b of the first drive protrusion 111 and before the exhaust main lift, for example, between 45 and 60 CrA ATDC, resulting in a valve lift of approximately 90 to 100 CrA ATDC. The first control valve 41 is de-energized between 300 and 330 CrA ATDC, and the exhaust unit 32 pushes the oil in the valve return brake units 31 and 31' back into the energy storage assembly 2, thereby returning the valve stem to the valve body. The de-energization time can be calibrated so that the exhaust unit 32 closes after 360 CrA ATDC of gas exchange (for example, around 405 CrA ATDC).

[0055] See also Figure 6 The figure shows the single-valve motion during the compression-release braking or early exhaust opening / closing phase. At this point, the first control valve 41 and the third control valve 43 are energized. Therefore, the ramp-up phase on the cam member 11 is transmitted to the single-valve piston 331, which pushes downward only on the exhaust unit 32, opening the cylinder exhaust passage. During this process, the brake unit 31' and the mechanical valve bridge 332 remain stationary in their base positions. In other words, the third control valve 43 controls the second control valve 42, transmitting the motion of the cam member 11 to the single-valve piston 331, thereby actuating the valve stem of only one exhaust unit, thus operating the corresponding cylinder in single-valve actuation mode.

[0056] The brake unit may include a piston unit, and the single valve piston 331 can interact with the piston of the piston unit of one brake unit 31, and the piston of the piston unit of the other brake unit 31' is connected to the mechanical valve bridge 332. The single valve piston 331 is movably connected to the mechanical valve bridge 332, so that the single valve piston 331 can move relative to the mechanical valve bridge 332 (for example, Figure 6 The mechanical valve bridge 332 moves downward in the middle of the exhaust valve to drive the valve stem of one exhaust unit, thereby operating the corresponding cylinder in the single-valve actuation mode. The mechanical valve bridge 332 can simultaneously drive the valve stems of two exhaust units, thereby operating the corresponding cylinders in the dual-valve actuation mode.

[0057] The second control valve 42 can switch the fluid connection state to:

[0058] For example, see Figure 6 The movement of the cam member 11 causes the oil in the pump oil chamber 123 to enter the piston unit of a brake unit 31, thereby driving the valve stem of an exhaust unit to move via the single valve piston 331, and the mechanical valve bridge 332 does not move, so that the corresponding cylinder works in the single valve drive mode; or, for example, see Figure 4The movement of the cam member 11 causes the oil in the pump oil chamber 123 to enter the piston unit of the other brake unit 31', thereby driving the mechanical valve bridge 332 to move, and the mechanical valve bridge 332 drives the valve stems of the two exhaust units to move, so that the corresponding cylinders work in the dual-valve drive mode.

[0059] For further information, see Figure 7 Combined with Figure 2 、 Figure 5 As shown in the figure, in the early opening (EEVO) and early closing (EEVC) functions, the first control valve 41 opens approximately 60 crank angle degrees earlier than in normal exhaust lift mode. Compared to the closing time in normal exhaust lift mode, the first control valve 41 closes approximately 30 crank angle degrees earlier, causing the exhaust unit 32 to close 10 to 30 degrees earlier (EEVC). EEVO and EEVC work together to increase exhaust temperature and residual gas in the engine cylinder.

[0060] See also Figure 8 Figure 2 shows the exhaust valve deactivation state in cylinder deactivation mode. At this point, the first control valve 41 and the third control valve 43 are both de-energized. Therefore, the movement of the cam member 11 is transmitted only to the energy storage assembly 2 and not to the brake unit 31 or 31'. In this state, the brake units 31, 31', the single-valve piston 331, and the mechanical valve bridge 332 remain in their reference positions and do not move.

[0061] Please also refer to Figure 9 Combined with Figure 8 、 Figure 2 As shown, during compression release, first control valve 41 is energized with a solenoid current starting at 460-470 CrA ATDC to produce a brake gas recirculation (BGR) valve lift of 480 CrA ATDC. The actual valve opening moment depends on the dynamic mechanical balance between in-cylinder pressure, exhaust manifold pressure, spring force, and the inertia of the moving mass.

[0062] Following the ramp-down phase during the BGR phase, the single-valve piston 331 returns to the base circle position of the cam member 11 at 600 CrA. Then, at 90 CrA BTDC during the next four-stroke engine cycle, the first ramp-up step 1a of the first drive lobe 111 of the cam member 11, which has been released from compression, begins, pushing the single-valve piston 331 open despite extremely high in-cylinder pressure (e.g., >60 barA). The valve remains open until the ramp-up phase of the third ramp-up step 1c of the first drive lobe 111 completes, at which point it begins to retract along the ramp-down step 1d.

[0063] Then the first control valve 41 current is cut off at 310~315 CrA ATDC, earlier than the exhaust main lift (Figure 5) or closed in advance ( Figure 7 ), the exhaust valve moves back to the reference position and closes at 390 ~ 400 CrA ATDC. Compared with the exhaust main lift or early closing, it is necessary to close the current earlier to prevent oil cavitation when the valve returns to the valve seat.

[0064] In summary, the continuously variable hydraulic valve mechanism for a heavy-duty engine of the present invention is achieved by providing a cam component 11 having a unique cam profile; and combining the cam component 11 with a control component 4, so that the continuously variable hydraulic valve mechanism can switch between single-valve and dual-valve drive; at the same time, by providing a control component 4 including multiple valve components located in different positions, the exhaust main lift or cylinder deactivation of the dual valve, as well as the compression release braking and early opening and closing of the exhaust valve of the single valve are further achieved.

[0065] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A heavy-duty engine in which cylinders can switch between single-valve actuation and dual-valve actuation, characterized in that: The invention comprises a hydraulic circuit (5) and a continuously variable hydraulic valve mechanism, wherein the continuously variable hydraulic valve mechanism is provided corresponding to each cylinder in the heavy-duty engine and comprises: A piston assembly (1) comprising a pump unit (12) and a cam member (11) drivingly connected to the pump unit; Energy storage component (2); A valve return brake assembly (3) comprising brake units arranged in pairs, two exhaust units (32, 32') arranged corresponding to the brake units, and a mechanical valve bridge assembly (33) arranged between the brake units and the exhaust units; A control assembly (4) comprising a first control valve (41) disposed between the energy storage assembly (2) and the piston assembly (1); a second control valve (42) disposed at one end of the valve return brake assembly (3); and a third control valve (43) disposed between the hydraulic circuit (5) and the continuously variable hydraulic valve mechanism; The mechanical valve bridge assembly (33) includes a single valve piston (331) connected to any one of the brake units and a mechanical valve bridge (332) connected to the other brake unit. The third control valve (43) is capable of controlling the second control valve (42) so that the movement of the cam member (11) is transmitted to the single valve piston (331), thereby driving only the valve stem of one exhaust unit, thereby causing the corresponding cylinder to operate in a single-valve drive mode. The third control valve (43) is also capable of controlling the second control valve (42) so that the movement of the cam member (11) is transmitted to the mechanical valve bridge (332), thereby driving the valve stems of two exhaust units, thereby causing the corresponding cylinder to operate in a dual-valve drive mode. The second control valve (42) is arranged on the exhaust valve of each engine cylinder head, and only one third control valve (43) is provided. The third control valve (43) is provided outside the cylinder head of the cylinder. One third control valve (43) and the second control valve (42) of each engine cylinder head are connected through an oil circuit to control the second control valve (42) of each cylinder. The outer peripheral edge of the cam member (11) is formed with a first drive protrusion and a second drive protrusion arranged at intervals, the first drive protrusion has three consecutive ramp-up steps and one ramp-down step, the three ramp-up steps and the one ramp-down step covering a crank angle of 470 degrees in total, the first ramp-up step (1a) of the first drive protrusion (111) covers the first compression release brake of the engine, the second ramp-up step (1b) of the first drive protrusion (111) starts from the end point of the first ramp-up step (1a), the second ramp-up step (1b) includes opening the exhaust valve in advance in the ignition mode so as to release the exhaust gas energy to the post-processing path earlier than in the normal main lift mode, the third ramp-up step (1c) of the first drive protrusion (111) is the longest ramp-up stage, covering the main lift opening sequence, the ramp-down step (1d) of the first drive protrusion (111) is a base circle returning to the cam member (11), The second driving protrusion is located between 480 and 600 crank angle degrees on the periphery of the cam member for brake gas recirculation, and the lift height of the brake gas recirculation portion is less than 2 mm so that the oil flow does not generate cavitation when the cam member (11) moves back to the base circle position during the ramp descent process.

2. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 1, characterized in that: The pump unit (12) comprises a pump roller (121) abuttingly connected to the cam member (11), a pump piston (122) connected to one end of the pump roller, a pump oil chamber (123) for accommodating the pump piston, and a pump spring (124) sleeved on the outer circumference of the pump piston.

3. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 2, characterized in that: The energy storage assembly (2) is connected to the first control valve (41) via an intermediate pressure chamber or a first channel (21); the energy storage assembly (2) comprises an accumulator oil chamber (22), an accumulator piston (23) movably connected in the accumulator oil chamber (22), and an accumulator spring (24) sleeved on the outer periphery of the accumulator piston (23); the accumulator spring (24) acts on the accumulator piston (23) to tend to make the oil in the accumulator oil chamber (22) flow toward the intermediate pressure chamber or the first channel (21).

4. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 3, characterized in that: The first control valve (41) is capable of controlling the connection or disconnection between the pump oil chamber (123) and the accumulator oil chamber (22). The first control valve (41) is energized after the cam member (11) rotates to the second ramp-up step (1b) and before the exhaust main lift, so that the valve lift is generated between 90 and 100 CrA ATDC. The first control valve (41) is de-energized between 300 and 330 CrA ATDC, and the exhaust unit pushes the oil in the valve return brake unit (31, 31') back to the accumulator assembly (2).

5. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 1, characterized in that: The first control valve is a 2 / 2 normally open solenoid valve; the second control valve is a 3 / 2-way mechanical valve; and the third control valve is a pilot 3 / 2-way solenoid valve.

6. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 2, characterized in that: The brake unit includes a piston unit, the single valve piston (331) can interact with the piston of the piston unit of one brake unit (31), the piston of the piston unit of the other brake unit (31') is connected to the mechanical valve bridge (332), the single valve piston (331) is movably connected to the mechanical valve bridge (332), so that the single valve piston (331) can move relative to the mechanical valve bridge (332) to drive the valve stem of one exhaust unit to move, and the mechanical valve bridge (332) can simultaneously drive the valve stems of two exhaust units to move when moving.

7. The heavy-duty engine with cylinders switchable between single-valve actuation and dual-valve actuation according to claim 6, characterized in that: The second control valve can switch the fluid connection state to enable: The movement of the cam member (11) causes the oil in the pump oil chamber (123) to enter the piston unit of the one brake unit, thereby driving the valve stem of the one exhaust unit to move via the single valve piston (331), and the mechanical valve bridge (332) does not move; or The movement of the cam member (11) causes the oil in the pump oil chamber (123) to enter the piston unit of the other brake unit, thereby driving the mechanical valve bridge (332) to move, and the mechanical valve bridge (332) drives the valve stems of the two exhaust units to move.

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