Variable valve drive system, engine assembly, and vehicle

Abstract

The application discloses a variable valve drive system, an engine assembly and a vehicle, and belongs to the technical field of engines.The variable valve drive system, the engine assembly and the vehicle have the advantages that the profile line of the first cam is different from the profile line of the second cam, so that when the first follower is in contact with the first cam, the second follower is separated from the second cam, and when the second follower is in contact with the second cam, the first follower is separated from the first cam, thereby avoiding abnormal sound caused by the back-and-forth switching of the first cam and the second cam.Meanwhile, when the hydraulic drive unit fails or is out of order, the second follower can be in contact with the second cam, so that the engine can work normally, and the reliability of the engine can be improved.

Description

Technical Field

[0001] The present invention relates to the field of engine technology, and in particular to a variable valve drive system, an engine assembly and a vehicle. Background Art

[0002] As the requirements for reducing fuel consumption and emissions of engines become increasingly stringent, the Miller cycle is realized through two different valve lifts, thereby achieving different intake volumes at different speeds, thereby improving engine performance, saving fuel, reducing emissions, improving engine power and reducing the risk of knock in gas engines caused by increased compression ratios.

[0003] However, although the existing variable valve drive system can achieve different valve lifts, it is prone to frequent cam switching, which may cause abnormal noise and even risk damage, affecting the reliability of the engine. Summary of the Invention

[0004] The object of the present invention is to provide a variable valve drive system, an engine assembly and a vehicle, which can avoid abnormal noise caused by frequent cam switching and improve the reliability of the engine.

[0005] To achieve the above objectives, the following technical solutions are provided:

[0006] Variable valve actuation system, including:

[0007] A rocker arm body, wherein a first end of the rocker arm body is provided with a first follower and a second follower, and a second end of the rocker arm body is used to drive the valve to open and close;

[0008] A rocker arm drive mechanism includes a drive shaft, and a first cam and a second cam fixed to the drive shaft, wherein the axes of the first cam and the second cam coincide with the axis of the drive shaft, and the profile of the first cam is different from the profile of the second cam; the profile is a curve representing the corresponding relationship between the cam angle and the valve lift;

[0009] The switching mechanism includes a hydraulic drive unit and an elastic member, wherein the driving end of the hydraulic drive unit is connected to the first follower to drive the first follower to extend along the first direction to a first circulation position through hydraulic pressure, so that the first follower contacts the first cam and the second follower is separated from the second cam, thereby making the lift of the valve a first lift H; the elastic member is configured to ensure that the first follower always has a movement tendency to retract along the first direction to a second circulation position. When the first follower is in the second circulation position, the first follower is separated from the first cam and the second follower is in contact with the second cam, thereby making the lift of the valve a second lift h, and h is not equal to H.

[0010] As a preferred technical solution of the above variable valve drive system, the hydraulic drive unit includes:

[0011] a hydraulic chamber, the hydraulic chamber being disposed in the rocker arm body;

[0012] A piston, wherein the first end of the piston is slidably disposed in the hydraulic cavity along the first direction, and the second end of the piston is located outside the hydraulic cavity and connected to the first follower; one end of the elastic member is connected to the rocker arm body, and the other end is connected to the second end of the piston.

[0013] As a preferred technical solution of the above-mentioned variable valve drive system, the rocker arm body is also provided with a limiting structure, and when the first follower is extended to the first circulation position along the first direction, the limiting structure is used to prevent the first follower from continuing to extend.

[0014] As a preferred technical solution of the above-mentioned variable valve drive system, the rocker arm body is further provided with an elephant foot, and the position of the elephant foot is adjustably arranged on the rocker arm body.

[0015] As a preferred technical solution of the above variable valve drive system, when the first follower is located at the second cycle position, a valve clearance a is provided between the rocker arm body and the valve;

[0016] When the first follower is located at the first cycle position, the rocker arm body is in contact with the valve.

[0017] As a preferred technical solution of the above-mentioned variable valve actuation system, the first follower includes a first roller, which is rotatably disposed on a driving end of the hydraulic drive unit; the second follower includes a second roller, which is rotatably disposed on the rocker arm body; and the radius of the first roller is equal to the radius of the second roller.

[0018] When the first roller is in the first circulation position, the distance between the first roller and the axis of the drive shaft is equal to the distance between the second roller and the axis of the drive shaft; the distance between the first circulation position and the second circulation position is b;

[0019] a≤H-h≤b.

[0020] As a preferred technical solution of the above-mentioned variable valve actuation system, the first follower includes a first roller, which is rotatably disposed on a driving end of the hydraulic drive unit; the second follower includes a second roller, which is rotatably disposed on the rocker arm body; and the radius of the first roller is equal to the radius of the second roller.

[0021] When the first roller is in the first circulation position, the distance between the first roller and the axis of the drive shaft is smaller than the distance between the second roller and the axis of the drive shaft; the distance between the first circulation position and the second circulation position is b;

[0022] The first roller further has a third position. When the first roller is in the third position, the distance between the first roller and the axis of the drive shaft is equal to the distance between the second roller and the axis of the drive shaft. The distance between the third position and the second circulation position is c.

[0023] ﹣(b-c)≤H-h≤c.

[0024] As a preferred technical solution of the above-mentioned variable valve actuation system, the first follower includes a first roller, which is rotatably disposed on a driving end of the hydraulic drive unit; the second follower includes a second roller, which is rotatably disposed on the rocker arm body; and a radius r1 of the first roller is greater than a radius r2 of the second roller.

[0025] When the first roller is in the first circulation position, the distance between the first roller and the axis of the drive shaft is smaller than the distance between the second roller and the axis of the drive shaft; the distance between the first circulation position and the second circulation position is b;

[0026] ﹣(r1-r2)≤H-h≤b-(r1-r2).

[0027] In order to achieve the above-mentioned purpose, an engine assembly is also provided, comprising an engine body and a variable valve drive system as described above, wherein the engine body comprises a valve that can be opened and closed, and the second end of the rocker arm body is used to drive the valve to open and close.

[0028] In order to achieve the above objectives, a vehicle is also provided, comprising the engine assembly as described above.

[0029] Compared with the prior art, the present invention has the following beneficial effects:

[0030] The variable valve actuation system, engine assembly, and vehicle of the present invention employ different profiles for the first and second cams, ensuring that when the first follower contacts the first cam, the second follower separates from the second cam, and vice versa, preventing the first follower from switching back and forth between the first and second cams and generating unusual noise. Furthermore, if the hydraulic drive unit malfunctions or fails, the second follower can contact the second cam, ensuring normal engine operation and improving engine reliability. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 Schematic diagram of the structure of a variable valve drive system in an embodiment of the present invention;

[0032] Figure 2 Schematic diagram of the structure of the rocker arm body and the switching mechanism in an embodiment of the present invention;

[0033] Figure 3 This is a structural diagram of the rocker arm drive mechanism in an embodiment of the present invention;

[0034] Figure 4 1 is a valve lift curve diagram for the large Miller cycle and the small Miller cycle in an embodiment of the present invention.

[0035] Reference numerals:

[0036] 1. Rocker arm body; 11. Limiting groove; 13. Elephant foot; 131. Locking nut;

[0037] 211, first roller; 212, first mounting seat; 2121, limit block;

[0038] 221, second roller; 222, second mounting seat;

[0039] 31. Drive shaft; 32. First cam; 33. Second cam;

[0040] 41. Piston; 42. Elastic member. DETAILED DESCRIPTION

[0041] To make the objectives, technical solutions, and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings herein can be arranged and designed in various different configurations.

[0042] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without creative effort shall fall within the scope of protection of the present invention.

[0043] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, it does not need to be further defined or explained in subsequent drawings.

[0044] In the description of the present invention, it should be noted that the terms "upper", "lower", "left", "right", "vertical", "horizontal", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, or are the orientation or position relationship in which the product of the invention is usually placed when in use. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first", "second", "third", etc. are only used to distinguish the description and cannot be understood as indicating or implying relative importance. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0045] In the description of the present invention, it should be noted that, unless otherwise specified or limited, the terms "disposed" and "connected" should be understood in a broad sense. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections. Those skilled in the art will understand the specific meanings of the above terms in the present invention based on the specific circumstances.

[0046] In the present invention, unless otherwise expressly specified or limited, a first feature being "above" or "below" a second feature may include the first and second features being in direct contact, or may include the first and second features being in contact not directly but through another feature between them. Furthermore, a first feature being "above," "above," and "above" a second feature may include the first feature being directly above or obliquely above the second feature, or may simply mean that the first feature is higher in level than the second feature. A first feature being "below," "below," and "below" a second feature may include the first feature being directly below or obliquely below the second feature, or may simply mean that the first feature is lower in level than the second feature.

[0047] The following describes embodiments of the present invention in detail. Examples of the embodiments 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 only to explain the present invention and are not to be construed as limiting the present invention.

[0048] like Figure 1-4As shown, the embodiment provides a variable valve drive system, which comprises a rocker arm body 1, a rocker arm drive mechanism and a switching mechanism, the first end of the rocker arm body 1 is provided with a first follower and a second follower at the same time, and the second end of the rocker arm body 1 is used to drive the valve to open and close; the rocker arm drive mechanism comprises a drive shaft 31, and a first cam 32 and a second cam 33 which are both fixed on the drive shaft 31, the axis of the first cam 32 and the axis of the second cam 33 are both coincided with the axis of the drive shaft 31, and the profile of the first cam 32 is different from the profile of the second cam 33; the profile is a curve representing the corresponding relationship between the cam angle and the valve lift; the switching mechanism comprises a hydraulic drive unit and an elastic piece 42, the driving end of the hydraulic drive unit is connected with the first follower, so as to drive the first follower to extend to a first cycle position in a first direction by hydraulic pressure, so that the first follower is in contact with the first cam 32, and the second follower is separated from the second cam 33, thereby making the lift of the valve be a first lift H; the elastic piece 42 is configured to make the first follower always have a movement tendency to retract to a second cycle position in the first direction, when the first follower is in the second cycle position, the first follower is separated from the first cam 32, and the second follower is in contact with the second cam 33, thereby making the lift of the valve be a second lift h, h is not equal to H.

[0049] The variable valve drive system of the embodiment, by setting the profile of the first cam 32 to be different from the profile of the second cam 33, so that when the first follower is in contact with the first cam 32, the second follower is separated from the second cam 33, and when the second follower is in contact with the second cam 33, the first follower is separated from the first cam 32, avoiding abnormal sound caused by the first cam 32 and the second cam 33 switching back and forth. At the same time, when the hydraulic drive unit fails or fails, the second follower can be in contact with the second cam 33, ensuring that the engine can work normally, thereby improving the reliability of the engine.

[0050] Exemplarily, the elastic piece 42 is a spring sheet, of course, the elastic piece 42 can also adopt other spring structures, which are not limited herein.

[0051] Optionally, the hydraulic drive unit comprises a hydraulic cavity and a piston 41, the hydraulic cavity is arranged in the rocker arm body 1; the first end of the piston 41 is slidably arranged in the hydraulic cavity in the first direction, the second end of the piston 41 is located outside the hydraulic cavity and connected with the second follower; one end of the elastic piece 42 is connected with the rocker arm body 1, and the other end is connected with the second end of the piston 41. In this way, it is not necessary to set an additional cylinder body, and the problem of leakage of the hydraulic drive unit can be avoided, the reliability of the hydraulic drive unit is improved, and the structure of the variable valve drive system is simplified.

[0052] Optionally, the rocker arm body 1 is further provided with a limiting structure. When the first follower extends to the first cycle position along the first direction, the limiting structure is used to prevent the first follower from continuing to extend, thereby improving the stability of the contact between the first follower and the first cam 32.

[0053] Optionally, a limit block 2121 is provided at the driving end of the hydraulic drive unit, and the limit structure includes a limit groove 11 provided on the rocker arm body 1. When the first follower extends to the first circulation position along the first direction, the limit block 2121 abuts against the limit groove 11 along the first direction. The structure is simple and easy to implement.

[0054] Optionally, the rocker arm body 1 is further provided with an elephant foot 13, and the position of the elephant foot 13 is adjustable on the rocker arm body 1. It should be noted that by adjusting the position of the elephant foot 13, the purpose of adjusting the valve clearance can be achieved.

[0055] When the hydraulic drive unit is not in operation, the first follower can retract to the second cycle position under the elastic force of the elastic member 42, so that the first follower is separated from the first cam 32, and the second follower is in contact with the second cam 33. At this time, the variable valve drive system forms a mechanical structure. In order to ensure the reliability of the engine, a valve clearance can be set between the elephant foot 13 and the valve.

[0056] When the hydraulic drive unit is activated, causing the first follower to contact the first cam 32 and the second follower to separate from the second cam 33, the variable valve drive system forms a hydraulic structure, which can automatically achieve overload protection without setting the valve clearance, thereby reducing the impact and noise problems caused by the existence of the valve clearance.

[0057] Specifically, one end of the elephant foot 13 is threadedly connected to the rocker arm body 1, and a locking nut 131 is provided on one end of the elephant foot 13. After loosening the locking nut 131, the position of the elephant foot 13 can be adjusted by rotating the elephant foot 13; tightening the locking nut 131 can lock the elephant foot 13 to the rocker arm body 1.

[0058] In this embodiment, when the first follower is located at the second cycle position, a valve clearance a is provided between the rocker arm body 1 and the valve; when the first follower is located at the first cycle position, the rocker arm body 1 is in contact with the valve.

[0059] It should be noted that when the hydraulic drive unit is activated and generates hydraulic pressure to drive the first follower to extend along the first direction to the first circulation position, due to the limiting effect of the limiting structure, the first follower will no longer continue to extend. At this time, under the reaction of the hydraulic pressure, the second end of the rocker arm body 1 will approach the valve so that the elephant foot 13 contacts the valve, thereby eliminating the valve clearance a.

[0060] In this embodiment, the first follower includes a first roller 211, which is rotatably provided at the driving end of the hydraulic drive unit. The second follower includes a second roller 221, which is rotatably provided at the rocker arm body 1. The radius of the first roller 211 is equal to the radius of the second roller 221. Furthermore, through the profile design of the first cam 32 and the profile design of the second cam 33, when the first follower contacts the first cam 32, the second follower is separated from the second cam 33, and when the second follower contacts the second cam 33, the first follower is separated from the first cam 32, which has the effect of reducing costs and facilitating design.

[0061] Furthermore, when the first roller 211 is in the first circulation position, the distance between the first roller 211 and the axis of the drive shaft 31 is equal to the distance between the second roller 221 and the axis of the drive shaft 31. In other words, the axis of the first roller 211 coincides with the axis of the second roller 221. At this point, the distance between the first circulation position and the second circulation position is b; thus, a ≤ H - h ≤ b.

[0062] In this embodiment, when the second roller 221 contacts the second cam 33 and the first follower is separated from the first cam 32, a small Miller cycle is achieved; the valve lift during the small Miller cycle is the second lift h. When the first follower contacts the first cam 32 and the second follower is separated from the second cam 33, a large Miller cycle is achieved; the valve lift during the large Miller cycle is the first lift H.

[0063] Because there is valve clearance a in the small Miller cycle, there is no valve clearance in the large Miller cycle. Figure 4 As shown, the black part is the valve lift curve in the large Miller cycle, and the red part is the actual valve lift curve after subtracting the valve clearance a in the small Miller cycle, that is, at any crankshaft angle, H-h≥a.

[0064] At any crankshaft angle, by limiting H-h≥a, it is possible to avoid switching noise caused by the second cam 33 contacting the second roller 221 during the large Miller cycle.

[0065] By limiting H-h≤b at any crankshaft angle, it is possible to avoid switching noise caused by the first cam 32 contacting the first roller 211 during the small miller cycle.

[0066] For example, if a=0.3 mm and b=4.5 mm, then 0.3 mm ≤ H - h ≤ 4.5 mm. This arrangement allows for a balance between the volume of the hydraulic chamber and the strength of the rocker arm body 1.

[0067] It should be noted that by limiting a≤H-h≤b, it is equivalent to limiting the profile of the first cam 32 and the profile of the second cam 33. The relationship between the profile of the first cam 32 and the valve lift during the large Miller cycle and the derivation method are existing technologies, and the relationship between the profile of the second cam 33 and the valve lift during the small Miller cycle and the derivation method are existing technologies, which will not be repeated here.

[0068] In summary, through the above-mentioned profile design of the first cam 32 and the profile design of the second cam 33, the valve clearance is retained during the small Miller cycle, and there is no valve clearance during the large Miller cycle; at the same time, during the large Miller cycle, only the first cam 32 is in contact with the first roller 211, and the second cam 33 is separated from the second roller 221; and during the small Miller cycle, only the second cam 33 is in contact with the second roller 221, and the first cam 32 is separated from the first roller 211, thereby avoiding switching noise.

[0069] Specifically, the first follower includes a first mounting seat 212, which is fixedly connected to the second end of the piston 41. The first roller 211 is rotatably connected to the first mounting seat 212. Furthermore, the second follower includes a second mounting seat 222, which is fixedly mounted on the rocker arm body 1. The second roller 221 is rotatably connected to the second mounting seat 222. Furthermore, a stopper 2121 is fixedly mounted on the first mounting seat 212 to prevent interference with the piston 41 and the first roller 211.

[0070] In other embodiments, the first follower includes a first roller, which is rotatably provided at the driving end of the hydraulic drive unit, and the second follower includes a second roller, which is rotatably provided at the rocker arm body, and the radius of the first roller is equal to the radius of the second roller; when the first roller is in the first circulation position, the distance between the first roller and the axis of the drive shaft is smaller than the distance between the second roller and the axis of the drive shaft; the distance between the first circulation position and the second circulation position is b; the first roller also has a third position, and when the first roller is in the third position, the first roller The spacing between the first cam and the first roller is equal to the spacing between the second roller and the axis of the drive shaft; the spacing between the third position and the second cycle position is c; -(b-c)≤H-h≤c, thereby also achieving the retention of valve clearance during the small Miller cycle and no valve clearance during the large Miller cycle; at the same time, achieving that during the large Miller cycle, only the first cam is in contact with the first roller, and the second cam is separated from the second roller; and during the small Miller cycle, only the second cam is in contact with the second roller, and the first cam is separated from the first roller, thereby avoiding switching noise.

[0071] For example, when b = 5mm, since the radius of the first roller is equal to that of the second roller, c = 4.5mm. When the first roller is in the first cycle position, the large Miller cycle is operating, and the axes of the large and small Miller rollers do not coincide. That is, the first roller is closer to the axis of the drive shaft than the second roller. In this case, the valve lash of the small Miller cycle is increased by 5mm - 4.5mm = 0.5mm during the large Miller cycle. To avoid interference caused by contact between the second cam and the second roller during the large Miller cycle, the valve lift during the small Miller cycle can be within 0.5mm greater than the valve lift during the large Miller cycle, i.e., h - H ≤ 0.5mm. Furthermore, when the first roller is in the second cycle position, the small Miller cycle is operating. The distance between the axes of the first and second rollers along the first direction, converted to the valve side, is H - h ≤ 4.5mm. Therefore, -0.5mm ≤ H - h ≤ 4.5mm.

[0072] In other embodiments, the first follower includes a first roller, which is rotatably provided at the driving end of the hydraulic drive unit; the second follower includes a second roller, which is rotatably provided at the rocker arm body; the radius r1 of the first roller is greater than the radius r2 of the second roller; when the first roller is located at the first cycle position, the distance between the first roller and the axis of the drive shaft is smaller than the distance between the second roller and the axis of the drive shaft; the distance between the first cycle position and the second cycle position is b; -(r1-r2)≤H-h≤b-(r1-r2), thereby also achieving the retention of valve clearance during the small Miller cycle and the absence of valve clearance during the large Miller cycle; at the same time, achieving the large Miller cycle, only the first cam contacts the first roller, and the second cam is separated from the second roller; and during the small Miller cycle, only the second cam contacts the second roller, and the first cam is separated from the first roller, thereby avoiding switching noise.

[0073] This embodiment also provides an engine assembly, including an engine body and a variable valve drive system as described above, wherein the engine body includes a valve that can be opened and closed, and the second end of the rocker arm body is used to drive the valve to open and close.

[0074] This embodiment also provides a vehicle including the above-mentioned engine assembly.

[0075] Note that the above are only preferred embodiments of the present invention and the technical principles employed. Those skilled in the art will understand that the present invention is not limited to the specific embodiments described herein, and that various obvious changes, readjustments, and substitutions can be made by those skilled in the art without departing from the scope of protection of the present invention. Therefore, although the present invention has been described in detail through the above embodiments, the present invention is not limited to the above embodiments and may include many other equivalent embodiments without departing from the concept of the present invention. The scope of the present invention is determined by the scope of the appended claims.

Claims

1. Variable valve actuation system, characterized in that: include: A rocker arm body (1), wherein a first end of the rocker arm body (1) is provided with a first follower and a second follower, and a second end of the rocker arm body (1) is used for driving the valve to open and close; A rocker arm drive mechanism comprises a drive shaft (31), and a first cam (32) and a second cam (33) both fixed on the drive shaft (31), wherein the axis of the first cam (32) and the axis of the second cam (33) both coincide with the axis of the drive shaft (31), and the profile of the first cam (32) and the profile of the second cam (33) are different; the profile is a curve representing the corresponding relationship between the cam angle and the valve lift; A switching mechanism comprises a hydraulic drive unit and an elastic member (42), wherein a driving end of the hydraulic drive unit is connected to the first follower to drive the first follower to extend in a first direction to a first circulation position by hydraulic pressure, so that the first follower contacts the first cam (32) and the second follower is separated from the second cam (33), thereby making the lift of the valve a first lift H; The elastic member (42) is configured to make the first follower always have a movement tendency to retract along the first direction to a second cycle position. When the first follower is in the second cycle position, the first follower is separated from the first cam (32), and the second follower is in contact with the second cam (33), thereby making the lift of the valve a second lift h, which is not equal to H. When the first follower is located at the second cycle position, a valve clearance a is provided between the rocker arm body (1) and the valve; When the first follower is located at the first cycle position, the rocker arm body (1) is in contact with the valve; The first driven member includes a first roller (211), the first roller (211) being rotatably disposed on a driving end of the hydraulic drive unit; the second driven member includes a second roller (221), the second roller (221) being rotatably disposed on the rocker arm body (1); the radius of the first roller (211) is equal to the radius of the second roller (221); When the first roller (211) is located at the first circulation position, the distance between the first roller (211) and the axis of the drive shaft (31) is equal to the distance between the second roller (221) and the axis of the drive shaft (31); the distance between the first circulation position and the second circulation position is b; a≤H-h≤b; Alternatively, the first follower comprises a first roller (211), the first roller (211) being rotatably disposed on a driving end of the hydraulic drive unit, and the second follower comprises a second roller (221), the second roller (221) being rotatably disposed on the rocker arm body (1), and the radius of the first roller (211) is equal to the radius of the second roller (221); When the first roller (211) is located at the first circulation position, the distance between the first roller (211) and the axis of the drive shaft (31) is smaller than the distance between the second roller (221) and the axis of the drive shaft (31); the distance between the first circulation position and the second circulation position is b; The first roller (211) further has a third position. When the first roller (211) is located at the third position, the distance between the first roller (211) and the axis of the drive shaft (31) is equal to the distance between the second roller (221) and the axis of the drive shaft (31). The distance between the third position and the second circulation position is c. ﹣(b-c)≤H-h≤c; Alternatively, the first driven member includes a first roller (211), the first roller (211) being rotatably disposed on a driving end of the hydraulic drive unit, the second driven member includes a second roller (221), the second roller (221) being rotatably disposed on the rocker arm body (1), and a radius r1 of the first roller (211) being greater than a radius r2 of the second roller (221); When the first roller (211) is located at the first circulation position, the distance between the first roller (211) and the axis of the drive shaft (31) is smaller than the distance between the second roller (221) and the axis of the drive shaft (31); the distance between the first circulation position and the second circulation position is b; ﹣(r1-r2)≤H-h≤b-(r1-r2).

2. The variable valve actuation system according to claim 1, characterized in that: The hydraulic drive unit comprises: A hydraulic chamber, the hydraulic chamber being arranged in the rocker arm body (1); A piston (41), wherein a first end of the piston (41) is slidably disposed in the hydraulic cavity along the first direction, and a second end of the piston (41) is located outside the hydraulic cavity and connected to the first follower; one end of the elastic member (42) is connected to the rocker arm body (1), and the other end is connected to the second end of the piston (41).

3. The variable valve actuation system according to claim 1, characterized in that: The rocker arm body (1) is further provided with a limiting structure, and when the first follower extends along the first direction to the first circulation position, the limiting structure is used to prevent the first follower from continuing to extend.

4. The variable valve actuation system according to claim 1, characterized in that: The rocker arm body (1) is further provided with an elephant foot (13), and the position of the elephant foot (13) is adjustable on the rocker arm body (1).

5. Engine assembly, characterized in that, The invention comprises an engine body and a variable valve drive system as claimed in any one of claims 1 to 4, wherein the engine body comprises a valve capable of opening and closing, and the second end of the rocker arm body (1) is used to drive the valve to open and close.

6. A vehicle, characterized in that Comprising the engine assembly as claimed in claim 5.

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