Valve drive mechanism

Abstract

The present application relates to a valve drive mechanism, which can realize flexible control of engine valve opening timing and opening lift, accurately realize consistency of valve opening design curve and actual curve, and is not affected by engine thermal state. The valve drive mechanism system has large rigidity, short response time, small valve seating impact, and valve opening parameters can be freely controlled in a large range, meeting the needs of different engine working conditions and various new combustion technologies.

Description

Technical Field

[0001] This invention relates to an engine valve train mechanism, specifically a camless valve drive mechanism for an engine, and more particularly to a valve drive mechanism. Background Technology

[0002] Variable valve timing mechanisms can adjust valve operating parameters, including valve opening timing and valve lift, according to different engine operating conditions, thereby improving engine performance under various conditions. Among all variable valve timing mechanisms, the camless valve actuation mechanism has the largest range of variable valve timing and valve lift. Most current camless valve actuation mechanisms use solenoid valves to control hydraulic oil to drive a piston, which in turn drives the valve. By varying the opening and closing times and the working cycle of the solenoid valve, different valve opening timings and valve lifts are obtained. However, in this system, to achieve partial valve opening, there is often a certain deviation between the actual valve curve and the design curve, and valve clearance compensation is also relatively complex. Summary of the Invention

[0003] The purpose of this invention is to propose a valve drive mechanism that uses an ECU to control a piezoelectric actuator, amplifying the stroke through a hydraulic chamber to open the valve. When a change in valve lift is required, the ECU controls a reduction in the maximum voltage input to the piezoelectric actuator, thereby reducing the actuator's stroke and consequently reducing the maximum valve lift, achieving partial lift valve movement. By controlling the voltage input to the piezoelectric actuator during valve seating, the pressure change in the hydraulic chamber is controlled, thus controlling the valve seating speed and reducing seating impact. Therefore, by adjusting the input voltage signal of the piezoelectric actuator through the ECU, valve timing and valve lift can be flexibly controlled, resulting in a valve operating curve with variable parameters and reliable operation, better meeting the engine's operating requirements. Through corresponding structural features, the actual valve curve during valve opening is made closer to the theoretical design curve, better meeting the engine's operating requirements.

[0004] The technical solution for achieving the objective of this invention is as follows:

[0005] A valve drive mechanism is provided, comprising a valve, a valve spring, a hydraulic cylinder, a one-way valve, a first O-ring seal, a first piston, a transmission mechanism, a piezoelectric actuator, a second O-ring seal, a second piston, and a hydraulic chamber; the first piston is larger than the second piston, and the first O-ring seal is larger than the second O-ring seal; the first O-ring seal is mounted on the first piston, and the second O-ring seal is mounted on the second piston; the hydraulic cylinder includes a first end and a second end; the first piston and the first O-ring seal are mounted on the first end of the hydraulic cylinder, and the second piston and the second O-ring seal are mounted on the second end of the hydraulic cylinder; a sealed hydraulic chamber is located between the first piston and the second piston. The mechanism is characterized in that: The hydraulic cylinder has at least one oil hole on its surface, and the one-way valve corresponding to the oil hole is installed inside the hydraulic cylinder to close the oil hole in one direction. One end of the transmission mechanism abuts against the piezoelectric actuator, and the other end abuts against the first piston. The part of the second end of the hydraulic cylinder that mates with the second piston has a generatrix composed of a straight segment and a curved segment. When the second piston mates with the straight segment, there is a slight leakage. When the second piston mates with the straight segment using the second O-ring seal, the second O-ring seal deforms to seal without leakage. When the first piston mates with the first end of the hydraulic cylinder using the first O-ring seal, there is no leakage.

[0006] Preferably, the piezoelectric actuator is controlled by the ECU, and the input voltage is determined by the ECU, which can be freely adjusted according to the engine's operating needs.

[0007] Preferably, the diameter ratio of the first piston and the second piston is determined by the working stroke of the piezoelectric actuator and the maximum opening of the valve.

[0008] Preferably, when cold, the second O-ring seal is located on the curved section at the second end of the hydraulic cylinder, and contacts the curved section in its natural shape to seal without leakage.

[0009] Preferably, the second O-ring is a flexible ring with an opening, made of metal.

[0010] Preferably, the curve segment includes one of the following curves: circular arc, hyperbola, parabola, involute, or a combination of the above curves.

[0011] Preferably, the oil hole is connected to the engine lubrication oil passage or a low-pressure oil source.

[0012] Preferably, the pressure generated by the lubricating oil or low-pressure oil source acting on the second piston is lower than the preload of the valve spring.

[0013] As another preferred embodiment, in the cold state, the second O-ring seal is located on the curved section at the second end of the hydraulic cylinder and does not contact the surrounding wall surface. This structure ensures accurate valve operation in the hot state, even when the valve clearance increases due to engine heat.

[0014] Compared with the prior art, the technical solution of the present invention has at least the following advantages:

[0015] The actual valve curve is closer to the theoretical design curve. When the engine is running, thermal changes are inevitable. To counteract the effects of thermal deformation on the valve train, hydraulic systems are often used. However, these hydraulic systems are prone to leakage. This leakage causes adaptive changes in valve clearance to offset the effects of thermal deformation, but it also affects the actual valve action curve; the higher the pressure, the greater the leakage and the greater the impact. In this invention, through the cooperation of sealing rings with corresponding curved and straight segments, a complete leak-free seal is achieved during valve opening, effectively ensuring that the actual valve curve more closely matches the theoretical design curve, thus improving engine performance.

[0016] This reduces valve seating impact. By controlling the voltage change of the piezoelectric actuator during valve seating, the valve seating action is completely limited by the hydraulic chamber pressure, ensuring seating speed while avoiding seating impact.

[0017] The valve lift curve is flexible and varied. The valve movement is entirely controlled by the small piston, which in turn is entirely controlled by the piezoelectric actuator. Therefore, by controlling the input voltage of the piezoelectric actuator, a flexible and varied valve lift curve can be obtained, enabling a wide range of changes in parameters such as valve opening timing and opening lift. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of a valve drive mechanism according to the present invention.

[0019] The labels in the attached diagram are as follows: 1 - Valve; 2 - Valve Spring; 3 - Second Piston; 4 - Hydraulic Cylinder; 5 - First O-Ring Seal; 6 - First Piston; 7 - Piezoelectric Actuator; 8 - Drive Rod; 9 - Oil Hole; 10 - Check Valve; 11 - Second O-Ring Seal Implementation

[0020] An embodiment of the present invention will be described in detail with reference to the accompanying drawings.

[0021] like Figure 1As shown, a valve drive mechanism includes a hydraulic cylinder 4. The surface of the hydraulic cylinder 4 has an oil hole 9 communicating with the engine's lubrication oil passage. A one-way valve 10 is installed inside the hydraulic cylinder 4 corresponding to the oil hole 9 to close the oil hole 9, allowing oil to flow only from the outside into the hydraulic cylinder. A first piston 6 is mounted at the first end of the hydraulic cylinder 4, and a first O-ring seal 5 is mounted on it to ensure a leak-free seal between the two. A second piston 3 is mounted at the second end of the hydraulic cylinder 4. The second end includes a cylindrical section with a straight generatrix and a conical section with a hyperbola generatrix, which are tangentially connected. The conical section is closer to the interior of the hydraulic cylinder 4, and the cylindrical section is closer to the exterior of the hydraulic cylinder 4. A second O-ring seal 11 is mounted at the end of the second piston 3 closest to the interior of the hydraulic cylinder 4. When the second piston 3 mates with the cylindrical section, there is a gap between them; when the second piston 3 mates with the cylindrical section using the second O-ring seal 11, the seal is leak-free due to the action of the second O-ring seal 11. A sealed hydraulic chamber exists between the first piston 6 and the second piston 3. The piezoelectric actuator 7 is controlled by the ECU and abuts against the first piston 6 via the transmission rod 8. The second piston 3 abuts against the valve 1 under the pressure of the hydraulic chamber.

[0022] When valve 1 is closed, the ECU inputs a low voltage or zero voltage to the piezoelectric actuator 7. At this time, the extension of the piezoelectric actuator 7 is minimal or remains at its initial size. Due to the influence of the one-way valve 10, the pressure in the hydraulic chamber is slightly lower than the engine lubrication pressure. At this time, because the force of the oil pressure acting on the first piston 6 and the second piston 3 is small, it can only ensure the contact between the transmission rod 8 and the first piston 6 and the piezoelectric actuator 7, and the contact between the second piston 3 and the valve 1, but it is less than the spring preload of the valve spring 2 in the valve closed state.

[0023] When valve 1 needs to open, the ECU controls a higher voltage input to the piezoelectric actuator 7. The piezoelectric actuator 7 deforms and elongates, pushing the first piston 6 through the transmission rod 8 to produce a small displacement, compressing the hydraulic chamber. This increases the pressure within the hydraulic chamber, thereby increasing the force acting on the second piston 3, overcoming the force of the valve spring 2, and opening valve 1. Since the diameter of the first piston 6 is much larger than the diameter of the second piston 3, the stroke of the second piston 3 is much greater than the displacement of the first piston 6. Furthermore, the piezoelectric actuator 7 has a fast response speed, a large driving force during deformation and elongation, and high displacement accuracy. Therefore, it can precisely control the displacement of the first piston 6, and thus control the stroke of the second piston 3, i.e., the opening degree of valve 1.

[0024] When valve 1 needs to be partially opened, the voltage input to the piezoelectric actuator 7 is controlled by the ECU, and the deformation elongation of the piezoelectric actuator 7 is appropriately shortened, thereby reducing the displacement of the first piston 6. At this time, the second piston 3 can make valve 1 partially open. At the same time, by maintaining this input voltage, the opening lift of valve 1 can be maintained. Therefore, the operating parameters of the valve can be adjusted over a wide range.

[0025] When valve 1 needs to be closed, the voltage of the ECU control input piezoelectric actuator 7 gradually decreases, and the deformation elongation of piezoelectric actuator 7 gradually decreases. At this time, under the action of valve spring 2, valve 1 pushes the second piston 3 back to its original position. The second piston 3 compresses the hydraulic chamber and pushes the first piston 6 back to its initial position. When approaching the valve seat position, by controlling the change of the input voltage of piezoelectric actuator 7, an appropriate seat speed and a low seat impact can be obtained at the same time.

[0026] Depending on the materials used in different engine components, the valve clearance of some engines increases while that of others decreases during normal operation in a hot state, compared to when they are cold. For engines with reduced valve clearance, when cold, the second O-ring seal 11, located on the curved section at the second end of the hydraulic cylinder 4, contacts the curved section in its natural shape, ensuring a leak-free seal. For engines with increased valve clearance, when cold, the second O-ring seal 11, located on the curved section at the second end of the hydraulic cylinder 4, does not contact the surrounding wall surface.

[0027] For engines with reduced valve clearance, the second end of the hydraulic cylinder is completely sealed and leak-free when cold. As the engine gradually reaches normal operating temperature, the valve clearance decreases, and the second piston 3 gradually moves upward, entering the interior of the hydraulic cylinder 4. Consequently, the second O-ring seal 11 mounted on the second piston 3 also moves upward. At the initial and final stages of each valve movement, the second O-ring seal does not contact the wall of the curved section. In other words, when the engine is in its normal operating hot state, a slight leakage may occur between the second O-ring seal 11 and the curved section of the hydraulic cylinder 4 at the instant the valve 1 opens and closes. However, as the valve 1 opens, the second O-ring seal 11 enters the straight section of the hydraulic cylinder 4, at which point there is no leakage. Therefore, during valve opening, the impact of leakage on the actual valve operating curve only exists at the instant the valve opens and closes. For the vast majority of the time, the hydraulic chamber is completely sealed, ensuring that the piezoelectric actuator 7 accurately transmits its action to the valve 1, making the actual valve operating curve perfectly consistent with the design curve. During normal operation in hot condition, leakage in the hydraulic cylinder is replenished by check valve 10, which allows oil to enter the hydraulic cylinder. When the engine returns from hot to cold, all components return to their original positions, including the second piston 3 and the second O-ring seal 11. Changes in the amount of oil are adjusted by the check valve.

[0028] For engines with increased valve clearance, in the cold state, the second O-ring seal 11 is located on the curved section of the second end of the hydraulic cylinder 4, without contact with the surrounding wall. This means that there may be a slight leakage at the second end of the hydraulic cylinder. As the engine gradually reaches normal operating temperature, the valve clearance increases, and the second piston 3 gradually moves downward. Therefore, the second O-ring seal 11 mounted on the second piston 3 also moves downward, its extreme position gradually moving from the curved section to the straight section. During this process, the volume change in the hydraulic chamber is completed sequentially by the increase in oil volume due to temperature factors and the oil replenishment by the one-way valve 10. When the engine is in the hot state of normal operation, the second O-ring seal 11 is located on the straight section, or its extreme position is in contact with the wall of the curved section, ensuring that the hydraulic cylinder 4 operates in a completely sealed state. Therefore, the action of the piezoelectric actuator 7 can be accurately transmitted to the valve 1, making the actual valve operating curve completely consistent with the design curve. When the engine returns to a cold state from a hot state, all components return to their original positions, including the second piston 3 and the second O-ring seal 11. If excessive oil flowed in during the process, leakage can be adjusted through the gap between the second O-ring seal and the conical section. During the state change, the pressure generated by the preload of the valve spring 2 on the second piston 3 is higher than the engine lubrication pressure, thus ensuring smooth operation.

[0029] Hydraulic cylinder 4 can be integrated with the cylinder head. The transmission mechanism can be directly driven by a transmission rod, or it can achieve the adjustment and transmission of action or force through other transmission methods such as levers. The second O-ring seal can also be made of metal material as an open elastic ring. When it is located in the conical section, there may be a small amount of leakage through the opening or the gap with the wall. When it is located in the straight section, there is no leakage at the opening and between the opening and the wall.

[0030] In the description of the embodiments of the present invention, it should be noted that expressions such as "first" and "second" are merely for distinguishing purposes and do not limit the order or arrangement of the contents they define, nor do they implicitly indicate the number of technical features indicated; they are only used to distinguish the defined components. Terms such as "upper," "lower," "inner," and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the embodiments of 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, or be constructed and operated in a specific orientation; therefore, they should not be construed as limitations on the embodiments of the present invention.

[0031] The present invention has been described above by way of example with reference to the accompanying drawings. Obviously, the specific implementation of the present invention is not limited to the above-described manner. Any improvements made using the inventive concept and technical solution of the present invention, or direct application to other occasions without modification, are all within the protection scope of the present invention.

Claims

1. A valve drive mechanism, comprising a valve, a valve spring, a hydraulic cylinder, a one-way valve, a first O-ring seal, a first piston, a transmission mechanism, a piezoelectric actuator, a second O-ring seal, a second piston, and a hydraulic chamber; wherein the first piston is larger than the second piston, the first O-ring seal is larger than the second O-ring seal, the first O-ring seal is mounted on the first piston, the second O-ring seal is mounted on the second piston, the hydraulic cylinder includes a first end and a second end, the first piston and the first O-ring seal are mounted on the first end of the hydraulic cylinder, the second piston and the second O-ring seal are mounted on the second end of the hydraulic cylinder, and a sealed hydraulic chamber is located between the first piston and the second piston, characterized in that: The hydraulic cylinder has at least one oil hole on its surface, and a one-way valve is installed inside the hydraulic cylinder corresponding to the oil hole to close the oil hole in one direction. One end of the transmission mechanism abuts against the piezoelectric actuator, and the other end abuts against the first piston. The generatrix of the second end of the hydraulic cylinder that mates with the second piston is composed of a combination of straight and curved segments. The straight segment is closer to the outside of the hydraulic cylinder, and the curved segment is closer to the inside of the hydraulic cylinder. When the second piston mates with the straight segment, there is a slight leakage. When the second piston mates with the straight segment using the second O-ring seal, the second O-ring seal deforms to seal and prevent leakage. When the first piston engages with the first end of the hydraulic cylinder using the first O-ring seal, there is no leakage. Compared to the cold state, in the normally operating hot state of an engine where the valve clearance is reduced, in the cold state, the second O-ring seal is located on the curved section of the second end of the hydraulic cylinder, making natural contact with the curved section to ensure a leak-free seal. In the normally operating hot state of an engine where the valve clearance is increased, in the cold state, the second O-ring seal is located on the curved section of the second end of the hydraulic cylinder and does not contact the surrounding wall. The extended end of the second piston abuts against the valve. The curved section includes one of the following: an arc, a hyperbola, a parabola, or an involute.

2. The valve drive mechanism according to claim 1, characterized in that: The piezoelectric actuator is controlled by the ECU, and the input voltage is determined by the ECU, which can be freely adjusted according to the engine's operating needs.

3. The valve drive mechanism according to claim 1, characterized in that: The diameter ratio between the first piston and the second piston is determined by the working stroke of the piezoelectric actuator and the maximum opening of the valve.

4. A valve drive mechanism according to claim 1, characterized in that: The second O-ring is an open elastic ring made of metal.

5. A valve drive mechanism according to claim 1, characterized in that: The oil hole is connected to the engine lubrication oil passage or a low-pressure oil source.

6. A valve drive mechanism according to claim 5, characterized in that: The pressure generated by the lubricating oil or low-pressure oil source acting on the second piston is lower than the preload of the valve spring.

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