Heavy-duty combustion engines

Abstract

The present invention relates to the field of combustion engines. The present invention provides a heavy-duty combustion engine. The heavy-duty combustion engine includes a variable hydraulic valvetrain. The variable hydraulic valvetrain combines a single cam member with a dedicated cam profile, a valve return brake assembly, and a switching solenoid valve to achieve two-stroke compression-release braking with simultaneous opening of both exhaust valves, as well as early exhaust valve opening and closing in normal ignition mode. Specifically, the cam profile of the cam member is configured to comprise four consecutive ramp-up stages, so that the four consecutive ramp-up stages encompass the compression release lift in the CRB1.5 compression-release braking mode, the early exhaust valve opening / closing in the ignition mode, and the exhaust main lift in the normal ignition mode.

Description

Technical Field

[0001] The present invention relates to the field of combustion engines, and in particular to a heavy-duty combustion engine. Background Art

[0002] Heavy-duty 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). The reciprocating piston performs negative work during the compression release process, thereby generating braking torque.

[0003] 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.

[0004] Regarding catalyst preheating measures, engine manufacturers are exploring the possibility of actively preheating the aftertreatment pathway by directly utilizing exhaust gas energy during idle conditions. 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, for single overhead cam (HOC) engines without individual cam phasing, active exhaust pathway warming must be achieved through valve lift switching.

[0005] In fact, the exhaust valve mechanism of current mainstream heavy-duty engines can usually only achieve one valve lift function, specifically by switching between different rocker arms through a variable valve mechanism.

[0006] In order 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 change of valve lift; although such an arrangement can achieve more than two valve lifts, since each valve lift requires independent rocker arm control, it is necessary to set up multiple rocker arms or cams in the heavy-duty engine. However, the combination of multiple rocker arms or cams will occupy the installation space of the heavy-duty engine, resulting in a large size of the equipment for installing the heavy-duty engine, which is not conducive to the installation and use of the heavy-duty engine.

[0007] In view of this, it is indeed necessary to provide an integrated valve mechanism for a heavy-duty engine to solve or alleviate one of the above problems. Summary of the Invention

[0008] An object of the present invention is to provide a heavy-duty combustion engine comprising a variable hydraulic valve mechanism which can achieve continuous changes in valve lift by integrating compression release braking, main lift and early opening / closing of the exhaust valve into a cam profile of a cam member, and by calibrating the rotation trajectory of the cam member and cutting off the hydraulic pressure between the cam member and the exhaust valve plunger.

[0009] To achieve the above-mentioned purpose of the invention, the present invention provides a heavy-duty combustion engine, which includes a variable hydraulic valve mechanism, and the variable hydraulic valve mechanism includes: a piston assembly, which is equipped with a cam component and a piston unit, and the cam component is circumferentially formed with four consecutive ramp-up stages and one ramp-down stage, and the ramp-up stage and the ramp-down stage together cover a crank angle of 550~570 degrees, and the piston unit includes a pump roller abutting against the outer peripheral edge of the cam component; an energy storage assembly; a valve return brake assembly, the valve return brake assemblies are arranged in pairs and connected to the exhaust valve, and the two valve return brake assemblies are connected as a whole through a hydraulic bridge; a switching solenoid valve for controlling the connection between the piston assembly, the energy storage assembly and the valve return brake assembly to achieve two-stroke compression release braking in which the two exhaust valves are opened at the same time, and early opening and closing of the exhaust valve in normal ignition mode.

[0010] As a further improvement of the present invention, the energy storage assembly is connected to the switching solenoid valve through an intermediate pressure chamber or a first channel, the hydraulic bridge is connected to the high-pressure oil chamber or the second channel of the piston unit of the piston assembly, and the high-pressure oil chamber or the second channel is connected to the switching solenoid valve. When the switching solenoid valve connects the high-pressure oil chamber or the second channel and the intermediate pressure chamber or the first channel, the movement of the cam component is transmitted to the energy storage assembly, disconnecting the valve return brake assembly and deactivating the exhaust valve; when the switching solenoid valve disconnects the connection between the high-pressure oil chamber or the second channel and the intermediate pressure chamber or the first channel, the movement of the cam component is transmitted to the valve return brake assembly to generate an exhaust lift.

[0011] As a further improvement of the present invention, each of the valve return brake assemblies includes a brake unit for an exhaust valve and an exhaust valve assembly, wherein the exhaust valve assembly includes a valve body, a valve stem, and an exhaust valve spring sleeved on the outer periphery of the valve stem, the hydraulic bridge is connected to the oil chamber of the valve body, and the exhaust valve spring applies force to the valve stem so that the valve stem tends to compress the oil chamber of the valve body.

[0012] As a further improvement of the present invention, the piston unit of the piston assembly also includes a pump piston connected to one side of the pump roller, a pump oil chamber for accommodating the pump piston, and a pump spring sleeved on the outer periphery of the pump piston, the high-pressure oil chamber or the second channel is connected to the pump oil chamber, and the pump spring presses the pump piston toward the cam member.

[0013] As a further improvement of the present invention, the switch solenoid valve is a 2 / 2 normally open solenoid valve.

[0014] As a further improvement of the present invention, the energy storage assembly includes an accumulator oil chamber, an accumulator piston movably connected to the accumulator oil chamber, and an accumulator spring sleeved on the outer periphery of the accumulator piston, the intermediate pressure chamber or the first channel is connected to the accumulator oil chamber, and the accumulator spring acts on the accumulator piston to tend to cause the oil in the accumulator oil chamber to flow to the intermediate pressure chamber or the first channel.

[0015] As a further improvement of the present invention, the compression stiffness of the exhaust valve spring is greater than the compression stiffness of the accumulator spring, so that when the switching solenoid valve connects the high-pressure oil chamber or the second channel and the intermediate pressure chamber or the first channel, the movement of the cam component is transmitted to the energy storage assembly rather than to the valve return brake assembly.

[0016] As a further improvement of the present invention, the first ramp-up phase of the cam member covers the first compression-release braking event of the heavy-duty engine; the second ramp-up phase of the cam member starts from the end point of the first ramp-up phase, including 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 phase of the cam member is the longest ramp-up phase, covering the main lift opening sequence; the fourth ramp-up phase of the cam member is the second engine compression-release braking event of the heavy-duty engine; the ramp-down phase of the cam member is the return to the base circle of the cam member.

[0017] The beneficial effects of the present invention include: the heavy-duty combustion engine of the present invention includes a variable hydraulic valve mechanism, which realizes two-stroke compression-release braking in which two exhaust valves are opened simultaneously and early opening and closing of the exhaust valve in normal ignition mode by combining a single cam component with a dedicated cam profile, a valve return brake assembly and a switching solenoid valve; specifically, by setting the cam profile of the cam component to consist of 4 consecutive ramp-up stages, the 4 consecutive ramp-up stages cover the compression release lift in the CRB1.5 compression-release brake mode, the early exhaust valve opening / closing in the ignition mode and the exhaust main lift in the normal ignition mode. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is a structural schematic diagram of a variable hydraulic valve mechanism of a heavy-duty combustion engine of the present invention.

[0019] Figure 2 yes Figure 1 A three-dimensional cross-sectional view of the variable hydraulic valve mechanism.

[0020] Figure 3 yes Figure 1 Schematic diagram of the structure of the cam component.

[0021] Figure 4 The working principle of the switch solenoid valve control is to produce exhaust lift.

[0022] Figure 5 The working principle of the on-off solenoid valve control is to deactivate both valve movements.

[0023] Figure 6 for Figure 3 The lift that can be generated by the middle cam member covers the crankshaft angle curve.

[0024] Figure 7 for Figure 3 The lift curve of each stage of the lift part of the cam component.

[0025] Figure 8 The current control curve of the switching solenoid valve during the exhaust lift and the expected in-cylinder pressure curve under normal ignition mode.

[0026] Figure 9 These are the solenoid valve current control curves in the exhaust valve early opening (EEVO) and exhaust valve early closing (EEVC) stages, and the cylinder pressure curve in the exhaust early opening and early closing mode.

[0027] Figure 10 The solenoid valve current control curve of the CRB1.5 compression-release brake function and the cylinder pressure curve of the two-stroke CRB1.5 compression-release brake are shown. DETAILED DESCRIPTION

[0028] 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.

[0029] 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.

[0030] 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.

[0031] 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.

[0032] See also Figure 1 and Figure 2 The heavy-duty engine provided by the present invention includes a variable hydraulic valve mechanism; the variable hydraulic valve mechanism of the present invention includes: a piston assembly 1, an energy storage assembly 2, a valve return brake assembly 3 connected to the exhaust valve, and a switch solenoid valve 4; the switch solenoid valve 4 is used to control the connection between the piston assembly 1, the energy storage assembly 2 and the valve return brake assembly 3; to achieve two-stroke compression release braking with the two exhaust valves opened at the same time, and early opening and closing of the exhaust valve in normal ignition mode.

[0033] The piston assembly 1 includes a cam member 11 and a piston unit 12 drivingly connected to the cam member 11. Figure 3 As shown, the cam component 11 is formed with four consecutive ramp-up stages (the first ramp-up stage 1a, the second ramp-up stage 1b, the third ramp-up stage 1c, and the fourth ramp-up stage 1d) and one ramp-down stage (1e) in the circumferential direction; the rising stage and the falling stage together cover a crank angle (CrA) of 550 to 570 degrees (i.e., a cam angle of 275 to 285 degrees).

[0034] Furthermore, the piston 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 piston assembly 1 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.

[0035] The accumulator assembly 2 is connected to the on-off solenoid valve 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 via the on-off solenoid valve 4. The accumulator assembly 2 includes an accumulator oil chamber 22, an accumulator piston 23 movably connected within 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.

[0036] The valve return brake assemblies 3 are arranged in pairs and connected to the exhaust valves. The two valve return brake assemblies 3 are connected as a whole through a hydraulic bridge 5 and connected to the high-pressure oil chamber or the second channel 13 of the piston assembly 1 through the hydraulic bridge 5. Furthermore, each valve return brake assembly 3 includes a brake unit 31 for the exhaust valve and an exhaust valve assembly 32, wherein the exhaust valve assembly 32 includes a valve body 321, a valve stem 322, and an exhaust valve spring 323 sleeved on the outer circumference of the valve stem 322. The hydraulic bridge 5 is connected to the oil chamber of the valve body 321. The exhaust valve spring 323 applies force to the valve stem 322 ( Figure 1 In the middle, the valve stem 322 is pressed upward, so that the valve stem 322 tends to compress the oil chamber of the valve body 321. Here, only the exhaust valve spring 323 is shown schematically. Figure 1 In the embodiment, the upper end of the exhaust valve spring 323 can act on the lower surface of the flange on the valve stem 322, and the lower end of the exhaust valve spring 323 can be supported by the housing (for example, the cylinder head or a support portion thereon).

[0037] The compression stiffness of the exhaust valve spring 323 can be greater than the compression stiffness of the accumulator spring 24, so that when the switching solenoid valve 4 connects the high-pressure oil chamber or the second channel 13 and the intermediate pressure chamber or the first channel 21, the movement of the cam member 11 is transmitted to the accumulator assembly 2 rather than to the valve return brake assembly 3, that is, the oil in the piston unit 12 enters the accumulator oil chamber 22 to compress the accumulator spring 24, rather than entering the valve body 321 to compress the exhaust valve spring 323.

[0038] Furthermore, the piston assembly 1, the energy storage assembly 2, and the valve return brake assembly 3 connected to the exhaust valve are connected to the switch solenoid valve 4. Specifically, when the switch solenoid valve 4 is energized, the switch solenoid valve 4 disconnects the connection between the high-pressure oil chamber or the second channel 13 and the intermediate pressure chamber or the first channel 21, and the movement of the cam member 11 is transmitted to the valve return brake assembly 3 (at Figure 4 , the valve stem 322 moves downward) to generate exhaust lift ( Figure 4 ); When the switch solenoid valve 4 is de-energized, the switch solenoid valve 4 connects the high-pressure oil chamber or the second channel 13 and the intermediate pressure chamber or the first channel 21, and the movement of the cam member 11 is transmitted to the energy storage assembly 2 to disconnect the valve return brake assembly 3 (that is, the oil in the intermediate pressure chamber or the first channel 21 does not enter the valve body 321), deactivating the exhaust valve ( Figure 5 ).

[0039] See Figure 3 Combined with Figure 6 、 Figure 7 As shown, in a four-stroke internal combustion engine, four consecutive ramp-up stages (the first ramp-up stage 1a, the second ramp-up stage 1b, the third ramp-up stage 1c, the fourth ramp-up stage 1d) and one ramp-down stage (1e) are formed on the outer peripheral edge of the cam component 11; together covering a crank angle of 550 to 570 degrees.

[0040] The first ramp-up phase 1a of the cam member 11 covers the first compression release braking event of the heavy-duty engine; it starts 50-60 CrA degrees before TDC ignition (0 CrA) and ends at a high point 3-5 CrA after TDC ignition.

[0041] Cam member 11's second ramp-up phase 1b begins at the end of first ramp-up phase 1a, 3 to 5 CrA after TDC (ATDC), and continues until 70 CrA ATDC, and then reaches 90 CrA ATDC. Second ramp-up phase 1b involves early exhaust valve opening in the ignition mode to release exhaust energy to the aftertreatment path earlier than in the normal main lift mode.

[0042] The third ramp-up phase 1c of the cam member 11 is the longest ramp-up phase and covers the main lift opening sequence. It starts from 90 CrA ATDC and gradually accelerates to 230 CrA ATDC, followed by a plateau until 315 CrA ATDC.

[0043] The fourth ramp-up phase 1d of the cam member 11 is the second engine compression release braking event for the heavy-duty engine; it starts from 315 CrA ATDC to 355 CrA ATDC and then reaches 365 CrA ATDC.

[0044] The ramp-down phase 1e is the base circle of the return cam member 11; it starts at 365 CrA ATDC and ends between 500 and 510 CrA ATDC.

[0045] Furthermore, when the switch solenoid valve 4 controls the operation of the variable hydraulic valve mechanism, the control strategies of the switch solenoid valve 4 used for compression release braking (CRB1.5), early exhaust valve opening / closing (EEVO / EEVC) and normal ignition exhaust main lift, and the number of times the switch solenoid valve 4 is energized are different; specifically, in the cases of early exhaust valve opening / closing (EEVO / EEVC) and normal ignition exhaust main lift, the switch solenoid valve 4 is energized and de-energized once in every four strokes; and in the case of compression release braking CRB1.5, the switch solenoid valve 4 is energized and de-energized twice in every 720° crankshaft.

[0046] See Figure 8 As shown, for the exhaust main lift, the on-off solenoid valve 4 is briefly energized after the second ramp-up phase 1b and before the exhaust main lift, for example, between 45 and 60 CrA ATDC. This results in a lift of approximately 90 to 100 CrA ATDC. The on-off solenoid valve 4 is deenergized between 270 and 30 CrA ATDC, causing the exhaust valve to push the oil in the valve return brake assembly 3 back into the accumulator assembly 2, thereby returning the exhaust valve to its seat. Simultaneously, the closing time can be calibrated so that the exhaust valve closes after TDC (for example, around 405 CrA ATDC).

[0047] See Figure 9 As shown in the figure, in the early opening (EEVO) and early closing (EEVC) functions, solenoid valve 4 is energized approximately 60 degrees crank angle earlier than in normal exhaust lift mode. Compared to the closing time in normal exhaust lift mode, solenoid valve 4 closes approximately 30 degrees crank angle earlier, resulting in an EEVC that advances exhaust valve closing by 10 to 30 degrees. EEVO and EEVC together increase exhaust temperature and residual gas in the cylinders of heavy-duty engines.

[0048] See Figure 10As shown in the figure, in a two-stroke compression-release braking function with two compression-release events, two exhaust opening moments occur during compression-release braking: First, switching solenoid valve 4 is energized starting at 90 CrA BTDC, generating the first valve lift at approximately 45 CrA BTDC. The actual valve opening event depends on the dynamic mechanical balance between in-cylinder pressure, exhaust manifold pressure, spring force, and inertia. Switching solenoid valve 4 is then de-energized at approximately 90 CrA ATDC, causing the exhaust valve to return to its base position and close at approximately 140 CrA ATDC. The second energization of the switching solenoid valve 4 starting from 290 CrA ATDC produces the second valve lift between 315 and 325 CrA ATDC; similarly, the actual valve opening event depends on the dynamic mechanical balance between the in-cylinder pressure, exhaust manifold pressure, spring force and the inertia of the moving mass. Then, the switching solenoid valve 4 is de-energized at 365 CrA ATDC, and the exhaust valve moves back to the reference position and closes at 380-390 CrA ATDC.

[0049] In summary, the variable hydraulic valve mechanism of the present invention combines a single cam member 11 with a dedicated cam profile, a valve return brake assembly 3, and a switching solenoid valve 4 to achieve two-stroke compression release braking with both exhaust valves open simultaneously, as well as early exhaust valve opening and closing in normal ignition mode. Specifically, by configuring the cam profile of the cam member 11 to consist of four consecutive ramp-up stages, these four consecutive ramp-up stages cover the compression release lift in the CRB1.5 compression release braking mode, early exhaust valve opening / closing in ignition mode, and the exhaust main lift in normal ignition mode. Furthermore, the variable hydraulic valve mechanism can also achieve dynamic cylinder deactivation (i.e., selective cylinder deactivation). Furthermore, by configuring the switching solenoid valve 4 as a 2 / 2-way high-speed solenoid valve, it switches the valve lift mode in accordance with the motion trajectory of the cam member 11, ensuring that both exhaust valves operate simultaneously during all valve lifts, including compression release braking.

[0050] 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 combustion engine, characterized in that A variable hydraulic valve train is provided, comprising: A piston assembly (1) is provided with a cam member (11) and a piston unit (12), wherein the cam member (11) is formed with four continuous ramp-up stages and one ramp-down stage in the circumferential direction, wherein the ramp-up stage and the ramp-down stage together cover a crank angle of 550 to 570 degrees, and the piston unit (12) includes a pump roller (121) abutting against the outer peripheral edge of the cam member (11); Energy storage component (2); Valve return brake assemblies (3), the valve return brake assemblies being arranged in pairs and connected to the exhaust valve, the two valve return brake assemblies (3) being connected as a whole via a hydraulic bridge (5); A switch solenoid valve (4) is used to control the connection between the piston assembly (1), the energy storage assembly (2) and the valve return brake assembly (3) to achieve two-stroke compression release braking with two exhaust valves opened simultaneously, and early opening and closing of the exhaust valve in a normal ignition mode. The energy storage assembly (2) is connected to the switch solenoid valve (4) via an intermediate pressure chamber or a first channel (21), the hydraulic bridge (5) is connected to the high-pressure oil chamber or the second channel (13) of the piston unit (12) of the piston assembly (1), and the high-pressure oil chamber or the second channel (13) is connected to the switch solenoid valve (4). When the switching solenoid valve (4) connects the high-pressure oil chamber or the second channel (13) and the intermediate pressure chamber or the first channel (21), the movement of the cam member (11) is transmitted to the energy storage assembly (2), the valve return brake assembly (3) is disconnected, and the exhaust valve is deactivated; when the switching solenoid valve (4) disconnects the connection between the high-pressure oil chamber or the second channel (13) and the intermediate pressure chamber or the first channel (21), the movement of the cam member (11) is transmitted to the valve return brake assembly (3) to generate an exhaust lift. The first ramp-up phase (1a) of the cam member (11) covers a first compression-release braking event of the heavy-duty engine; The second ramp-up phase (1b) of the cam member (11) starts from the end of the first ramp-up phase (1a) and includes opening the exhaust valve early in the ignition mode to release exhaust gas energy to the aftertreatment path earlier than in the normal main lift mode; The third ramp-up phase (1c) of the cam member (11) is the longest ramp-up phase, covering the main lift opening sequence; The fourth ramp-up phase (1d) of the cam member (11) is a second engine compression release braking event of the heavy-duty engine; The ramp-down phase of the cam member (11) is a return to the base circle of the cam member (11).

2. The heavy-duty combustion engine according to claim 1, characterized in that Each of the valve return brake assemblies (3) comprises a brake unit (31) for an exhaust valve and an exhaust valve assembly (32), wherein the exhaust valve assembly (32) comprises a valve body (321), a valve stem (322), and an exhaust valve spring (323) sleeved on the periphery of the valve stem (322); the hydraulic bridge (5) is connected to the oil chamber of the valve body (321); the exhaust valve spring (323) applies force to the valve stem (322), causing the valve stem (322) to tend to compress the oil chamber of the valve body (321).

3. The heavy-duty combustion engine according to claim 1, characterized in that The piston unit (12) of the piston assembly (1) further includes 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 on the outer periphery of the pump piston (122), the high-pressure oil chamber or the second channel (13) being connected to the pump oil chamber (123), and the pump spring (124) pressing the pump piston (122) toward the cam member (11).

4. The heavy-duty combustion engine according to claim 1, characterized in that The switch solenoid valve (4) is a 2 / 2 normally open solenoid valve.

5. The heavy-duty combustion engine according to claim 2, characterized in that The energy storage 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 on the outer periphery of the accumulator piston (23); the intermediate pressure chamber or the first channel (21) is connected to the accumulator oil chamber (22); the accumulator spring (24) acts on the accumulator piston (23) to tend to make the oil in the accumulator oil chamber (22) flow to the intermediate pressure chamber or the first channel (21).

6. The heavy-duty combustion engine according to claim 5, characterized in that The compression stiffness of the exhaust valve spring (323) is greater than the compression stiffness of the accumulator spring (24), so that when the switch solenoid valve (4) connects the high-pressure oil chamber or the second channel (13) and the intermediate pressure chamber or the first channel (21), the movement of the cam member (11) is transmitted to the energy storage assembly (2) rather than to the valve return brake assembly (3).

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