Cam decompression mechanism

Abstract

This solution discloses a cam-driven pressure-reducing mechanism, including a camshaft and a swing block. The swing block can swing from a pressure-reducing position to a release position under centrifugal force, and return from the release position to the pressure-reducing position under the action of a spring force parallel to the camshaft axis. The swing axis is perpendicular to the camshaft axis. A pin is fixed radially along the camshaft, and the swing block is pinned with the pin as the swing axis. A radially penetrating mounting hole for the swing block is provided on the camshaft, and the swing block passes through the mounting hole. With the pin as the boundary, one end of the swing block is the heavy part, and the other end is the light part, with the mass of the heavy part being greater than the mass of the light part. The beneficial effects of this solution are: 1. Higher sensitivity while meeting functional requirements; 2. Effective reduction of the weight of the swing block, meeting the requirements of lightweight design; 3. Setting the spring force direction parallel to the camshaft axis eliminates torque during high-speed rotation and extends the service life of the spring.

Description

Technical Field

[0001] This utility model relates to the field of vehicle engines, specifically a cam decompression mechanism. Background Technology

[0002] Chinese patent document CN114278408A, published on April 5, 2022, discloses a decompression structure for an engine camshaft. This structure is located at the camshaft and valve tappet and includes a spring and a sway block. A mounting hole is provided on the side wall of the camshaft. The sway block is oscillatingly connected to the mounting hole and has a drive unit. When the sway block oscillates under the force of the spring, the drive unit extends beyond the outer circumferential surface of the cam base circle portion of the camshaft and acts on the end face of the valve tappet. When the camshaft rotates, the sway block overcomes the spring force under centrifugal force and oscillates in the opposite direction, moving the drive unit away from the valve tappet. This engine camshaft decompression structure has the advantage of occupying little space.

[0003] In practical applications, this existing technology has two drawbacks: First, the swing block is connected to the side wall of the camshaft via a tension spring. Therefore, the swinging part of the swing block needs to have a large mass to generate a centrifugal force sufficient to overcome the tension of the tension spring. The total mass of the swing block is added to the total mass of the camshaft. The larger the total mass of the camshaft, the greater the inertia, which is less conducive to the rapid start and stop of the camshaft rotation. This is contrary to the purpose of the invention. Second, the tension direction of the tension spring forms a large angle with the rotation direction of the camshaft. When rotating at high speed, the tension spring is subjected to force not only in the direction of elasticity but also to torque in the direction of rotation. This force is continuous when the camshaft rotates, which can easily lead to damage to the tension spring, resulting in structural failure. The swing block is difficult to reset, and the decompression effect fails. Summary of the Invention

[0004] To address the above problems, this utility model provides a cam pressure reduction mechanism that eliminates the aforementioned defects, improves service life, and optimizes performance.

[0005] To achieve the purpose of this invention, the present invention adopts the following technical solution: A cam-driven pressure reduction mechanism, comprising a camshaft and a sling block. The swing block can swing from the decompression position to the swing open position under the action of centrifugal force, and return from the swing open position to the decompression position under the action of elastic force parallel to the camshaft axis; the swing shaft is perpendicular to the camshaft axis.

[0006] Preferably, the pin is fixed radially along the camshaft, and the swing block is pinned with the pin as the swing axis.

[0007] Preferably, the camshaft is provided with a radially penetrating hole for a slinger, and the slinger passes through the hole.

[0008] Preferably, with the pin as the boundary, one end of the throwing block is the heavy part of the throwing block, and the other end is the light part of the throwing block, with the mass of the heavy part of the throwing block being greater than the mass of the light part of the throwing block.

[0009] Preferably, the lightweight part of the sling block abuts against the elastic element, and the elastic force of the elastic element is parallel to the axial direction of the camshaft.

[0010] Preferably, the camshaft has a top pin hole, the hole axis of which is parallel to the axial direction of the camshaft; the elastic element is a top pin spring installed in the top pin hole; the outer end of the top pin spring abuts against the lightweight part of the swing block.

[0011] Preferably, the top pin hole is a blind hole, and the inner end of the top pin spring abuts against the bottom of the blind hole.

[0012] Preferably, the top pin hole is a through hole, and a limiting bolt is installed at the other end of the through hole, with the inner end of the top pin spring abutting against the top of the limiting bolt.

[0013] Preferably, it also includes a return pin installed in the pin hole; the bottom of the return pin is connected to the pin spring, and the top is smooth and abuts against the lightweight part of the throwing block.

[0014] Preferably, at least one of the camshaft and the swivel block is provided with a limiting structure to prevent the swivel block from swinging beyond its limit.

[0015] The beneficial effects of this plan are: 1. Higher sensitivity while meeting functional requirements; 2. It can effectively reduce the weight of the slingshot and meet the requirements of lightweight design. 3. Set the spring force direction to be parallel to the camshaft axis to eliminate torque during high-speed rotation and extend the spring's service life. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the structure of this utility model in the pressure-reducing position; Figure 2 This is an axial sectional view of the camshaft in the decompression position according to this utility model; Figure 3 This is a schematic diagram of the structure of this utility model in the open position; Figure 4 This is an axial sectional view of the camshaft in the open position of this utility model.

[0017] Among them: camshaft 1, slinger mounting hole 2, slinger 3, slinger heavy part 31, slinger light part 32, slinger limiting part 33, pin 4, top pin hole 5, top pin spring 6, return top pin 7, limiting bolt 8, camshaft side limiting part 9, valve rocker arm 98, valve 99. Detailed Implementation

[0018] The present invention will now be further described with reference to the accompanying drawings and specific embodiments.

[0019] Example 1 Example 1 details a cam decompression mechanism applied to a certain type of motorcycle engine. This mechanism plays a key role in regulating valve pressure and optimizing engine performance during engine operation.

[0020] Combination Figure 1 An overall observation of the camshaft decompression mechanism reveals that it is mainly composed of core components such as the camshaft 1, the rocker arm 3, the valve rocker arm 98, and the valve 99. These components work together to achieve the decompression function, ensuring the stable operation of the engine under different operating conditions.

[0021] Figure 2 What is presented is Figure 1 The axial sectional view of the camshaft in its current state is shown. To clearly illustrate the internal structure, the valve rocker arm 98 and valve 99 are not shown. This sectional view clearly shows a through-hole 2 for the camshaft 1, running radially through it. A pin 4 is securely fixed between the two side walls of the through-hole 2, ensuring that the axis of the pin 4 is perpendicular to the axis of the camshaft 1. The through-hole 3 is precisely inserted into the through-hole 2 and secured by the pin 4 at a slightly lower position within it. This design allows the through-hole 3 to swing flexibly around the pin 4, providing a structural basis for the subsequent decompression function.

[0022] In this embodiment, the swing block 3 adopts a unique eccentric structure design. Specifically, with the pin 4 as the dividing point, the part above the pin 4 is defined as the heavy part 31 of the swing block, and the part below the pin 4 is the light part 32 of the swing block. Through careful design, the mass of the heavy part 31 is significantly greater than that of the light part 32, and the mass ratio of the two is precisely set to 3:1. This ratio is not arbitrarily determined, but is scientifically selected and precisely determined by those skilled in the art after comprehensively considering many relevant parameters such as the rotational speed of the camshaft 1 and the elastic force of the spring, in order to ensure that the swing block 3 can swing in the expected manner under different working conditions, thereby achieving the ideal pressure reduction effect. Under normal conditions, the light part 32 of the swing block is subjected to elastic force, the direction of which is parallel to the axial direction of the camshaft 1, so that the swing block 3 is in a state of... Figure 1 The decompression position is shown. At this time, the end of the lightweight part 32 of the sling block is exactly located on the valve rocker arm 98, which can stably hold the valve 99, maintain the decompression state of the engine, and create favorable conditions for the smooth start of the engine. From the perspective of structural principle, the heavy part 31, the lightweight part 32 of the sling block, and the pin 4 together form a seesaw-like structure. This structure cleverly utilizes the principle of mechanics, so that the sling block 3 can swing flexibly under the action of elastic force and centrifugal force.

[0023] The working principle of this cam-driven pressure-reducing mechanism is based on mechanical balance and motion conversion. When the camshaft 1 is stationary, i.e., not rotating, the elastic force becomes the dominant force, applied to the lightweight part 32 of the throwing block. Due to the elastic force, the throwing block 3 is stably held in the pressure-reducing position, such as... Figure 1 As shown. At this time, the end of the lightweight part 32 of the rocker arm is in close contact with the valve rocker arm 98, thereby pressing against the valve 99, keeping the engine in a depressurized state, reducing starting resistance, and facilitating smooth engine starting.

[0024] However, the situation changes significantly when the camshaft 1 begins to rotate at high speed. Due to its large mass, the heavy weight section 31 of the sling block generates a strong outward (axially outward) sling force under centrifugal force. This sling force is transmitted through a seesaw structure, causing the sling block 3 to overcome the elastic force and swing counterclockwise. As the rotational speed of the camshaft 1 increases, the swing amplitude of the sling block 3 gradually increases until it reaches the final position of the swing, at which point the corresponding state is as follows: Figure 3 , Figure 4 As shown. At the end of the swing, the end of the lightweight part 32 of the swing block completely leaves the position above the corresponding valve rocker arm 98, and no longer exerts pressure on the valve 99, thereby releasing the decompression state and enabling the engine to operate under normal pressure, achieving the purpose of normal engine operation after startup.

[0025] When the engine stops running, the speed of camshaft 1 drops rapidly to zero, and the centrifugal force disappears. At this time, the elastic force becomes the dominant force again, driving the swing block 3 to swing back to its original position. Figure 1 The decompression state shown prepares the engine for the next start. This cyclical working mode allows the camshaft decompression mechanism to automatically adjust valve pressure according to different engine operating conditions, effectively improving engine performance and reliability.

[0026] This embodiment is the basic embodiment of this solution. Subsequent embodiments will be evolved and optimized based on this embodiment.

[0027] Example 2 Based on the cam pressure reduction mechanism constructed in Example 1, Example 2 has undergone a more in-depth and innovative evolution and optimization, aiming to further improve the mechanism's performance, enhance operational stability, and optimize the overall design.

[0028] In this embodiment, a key improvement was made to the internal structure of the camshaft 1 by adding a top pin hole 5. Combined with... Figure 2A detailed analysis revealed that the axial direction of the top pin hole 5 was carefully designed to be parallel to the axial direction of the camshaft 1. This design layout not only makes full use of the internal space of the camshaft 1, but also ensures that the subsequently installed components can operate in coordination with the overall structure, avoiding interference problems caused by inconsistent orientations, and laying the foundation for the stable operation of the entire pressure reduction mechanism.

[0029] A top pin spring 6 and a return pin 7 are installed inside the top pin hole 5. These two components work together and play a crucial role in the pressure reduction mechanism. The return pin 7 is precisely installed inside the top pin hole 5, and its left end is designed with a smooth shape. This end cleverly extends out of the left side of the top pin hole 5 and makes tight contact with the lightweight part 32 of the swing block. This contact method ensures that the return pin 7 can transmit the force to the lightweight part 32 of the swing block in a timely and accurate manner, thereby achieving effective control over the swing position of the swing block 3.

[0030] The installation method of the top pin spring 6 is closely related to the structure of the top pin hole 5. Depending on the different designs of the top pin hole 5, the right end of the top pin spring 6 has two specific design schemes. One is... Figure 2 As clearly shown, the top pin hole 5 is a through-hole design. In this design, the right end of the hole is threaded onto a limiting bolt 8, and the right end of the top pin spring 6 is securely T-sleeved onto the left end of the limiting bolt 8. This design has significant advantages; by simply screwing the limiting bolt 8 in or out, the position of the limiting bolt 8 within the top pin hole 5 can be precisely adjusted, thereby changing the initial compression of the top pin spring 6 and achieving flexible adjustment of the spring force. This adjustability allows the pressure-reducing mechanism to optimize the spring force of the top pin spring 6 according to different engine operating conditions, usage environments, and performance requirements, ensuring the mechanism maintains good working condition under various conditions. Secondly, although not shown in the figure, the top pin hole 5 can also be designed as a blind hole. In a blind hole design, the right end of the top pin spring 6 directly abuts against the bottom of the blind hole. This design simplifies the structure, reduces the use of one part (the limiting bolt 8), and has significant advantages in cost control and ease of installation. For some applications that are more sensitive to cost and have relatively low requirements for elasticity adjustment, this blind hole design is a more economical and practical choice.

[0031] Regardless of which scheme is adopted, the working principle of the cam decompression mechanism is consistent at different speeds of the camshaft 1. When the camshaft 1 rotates at high speed, the swashplate 3 is subjected to a strong centrifugal force, causing it to swing counterclockwise. During the swing, the lightweight part 32 of the swashplate overcomes the elastic force of the top pin spring 6 and displaces to the right. This displacement further drives the return top pin 7 to move to the right along the top pin hole 5, causing the top pin spring 6 to be further compressed and storing elastic potential energy. At this time, the swing of the swashplate 3 changes the state of the valve rocker arm 98 and the valve 99, releasing the decompression state and meeting the normal intake and exhaust requirements of the engine during high-speed operation.

[0032] However, as the rotational speed of camshaft 1 gradually decreases until it stops, the situation reverses. The centrifugal force decreases rapidly with the reduction in rotational speed. When the elastic force of the top pin spring 6 exceeds the centrifugal force, the top pin spring 6 begins to release its stored elastic potential energy, pushing the return top pin 7 to the left. This leftward movement of the return top pin 7 then pushes the lightweight part 32 of the swing block, causing the swing block 3 to return to its original position. Figure 4 The pressure reduction position is shown. During this process, the coordinated action of the top pin spring 6 and the return top pin 7 ensures that the throwing block 3 can accurately and quickly return to the initial position, preparing for the next engine start and ensuring the cyclical and reliable operation of the entire pressure reduction mechanism.

[0033] Through these improvements and optimizations in Example 2, the cam pressure reduction mechanism has achieved a significant performance enhancement. The adjustable top pin spring 6 design allows the mechanism to better adapt to different working conditions, improving the engine's versatility and adaptability; while the two different top pin hole 5 designs provide more options for practical applications, meeting the needs of different users in terms of cost, installation, and maintenance. These improvements work together to further enhance the stability and reliability of the cam pressure reduction mechanism in motorcycle engines, providing a strong guarantee for the engine's efficient operation.

[0034] Same as Example 1.

[0035] Example 3 Based on the technical achievements of Example 2, Example 3 carried out more refined and targeted further optimization work, aiming to comprehensively improve the performance stability, operational safety and manufacturing convenience of the cam pressure reduction mechanism.

[0036] In this embodiment, an innovative limiting structure is added to prevent the swing block 3 from exceeding its limit. This improvement is a key element in ensuring the reliable operation of the mechanism. Combined with... Figure 2Upon closer examination, a small protrusion is carefully designed and formed on the far left of the heavy mass section 31 of the swing block 3. This protrusion is defined as the swing block limiting part 33. The size, shape, and position of this swing block limiting part 33 have been rigorously calculated and verified through multiple simulations to ensure that it can function accurately and effectively during the swing of the swing block 3.

[0037] Meanwhile, a camshaft-side limiting part 9 is cleverly positioned on the camshaft 1, corresponding to the sway block limiting part 33. When the camshaft 1 rotates at high speed, and the sway block 3 swings counterclockwise under centrifugal force, the sway block limiting part 33 will continuously approach the camshaft-side limiting part 9 as the swing amplitude gradually increases. When the sway block 3 reaches its maximum counterclockwise swing amplitude, the sway block limiting part 33 just touches the camshaft-side limiting part 9. At this point, the camshaft-side limiting part 9 acts like a solid barrier, effectively limiting the further swing of the sway block 3 and preventing it from exceeding its design range due to excessive swing, thereby avoiding serious problems such as component damage and mechanism jamming. The state of the mechanism at this time can be seen in [reference needed]. Figure 4 As shown in the figure, it can be clearly seen that the sling block limiting part 33 and the camshaft side limiting part 9 are in contact with each other and together maintain the stable position of the sling block 3.

[0038] It is worth mentioning that this example employs a highly innovative and practical design concept, utilizing the side wall of the cam as the camshaft-side limiting part 9. This design has several significant advantages. From a manufacturing process perspective, it cleverly utilizes the structure of existing components, eliminating the need for additional machining of specialized limiting parts, greatly reducing machining steps, improving production efficiency, and lowering manufacturing costs. In traditional limiting structure designs, a separate limiting block or other limiting device often needs to be machined and precisely installed onto the camshaft. This not only increases machining difficulty and time but may also affect the limiting effect due to installation errors. The design in this embodiment completely avoids these problems, achieving structural simplification and process optimization.

[0039] From a structural compactness perspective, utilizing the side wall of the cam wheel as a limiting part avoids adding extra volume and weight to the mechanism, making the entire cam decompression mechanism more compact and lightweight. This is particularly important for applications like motorcycle engines where space and weight requirements are stringent, helping to improve overall engine performance and fuel economy.

[0040] From a reliability and stability perspective, the camshaft, as a key moving component in the engine, has a wheel side wall with high strength and wear resistance. Using it as the camshaft-side limiting part 9 ensures that it maintains good limiting performance under the long-term and frequent oscillating impact of the sway block 3, and is not prone to wear or deformation problems, thereby effectively extending the service life of the mechanism and improving operational reliability.

[0041] Example 3, by adding a limiting structure to prevent the swing block 3 from exceeding its limit and cleverly using the side wall of the cam wheel as the camshaft side limiting part 9, has achieved significant results in ensuring the safe operation of the mechanism, optimizing the manufacturing process, improving the structural compactness, and enhancing reliability, laying a solid foundation for the further development and application of cam pressure reduction mechanisms.

[0042] Same as Example 2.

[0043] This solution can also be improved in several ways. For example, the top pin spring 6 can be positioned opposite, corresponding to the heavy part 31 of the throwing block, or the top pin spring 6 can be a tension spring, moved to the opposite side of the light part 32 of the throwing block, and so on. Those skilled in the art can select the specific structure and configure the specific parameters according to actual design needs.

Claims

1. A cam-driven pressure-reducing mechanism, comprising a camshaft (1) and a slinger (3), characterized in that, The swing block (3) can swing from the decompression position to the swing open position under the action of centrifugal force, and return from the swing open position to the decompression position under the action of elastic force parallel to the axial direction of the camshaft (1); the swing shaft is perpendicular to the axial direction of the camshaft (1).

2. The cam pressure reduction mechanism according to claim 1, characterized in that, The pin (4) is fixed radially along the camshaft (1), and the swing block (3) is pinned with the pin (4) as the swing axis.

3. The cam pressure reduction mechanism according to claim 2, characterized in that, A camshaft (1) is provided with a radially penetrating hole (2), and a sling block (3) is inserted into the sling block mounting hole (2).

4. The cam pressure reduction mechanism according to claim 3, characterized in that, With the pin (4) as the boundary, one end of the throwing block (3) is the heavy part (31) and the other end is the light part (32). The mass of the heavy part (31) is greater than the mass of the light part (32).

5. A cam pressure reduction mechanism according to claim 4, characterized in that, The lightweight part (32) of the sling block abuts against the elastic element, and the elastic force of the elastic element is parallel to the axial direction of the camshaft (1).

6. A cam pressure reduction mechanism according to claim 5, characterized in that, The camshaft (1) is provided with a top pin hole (5), and the hole axis of the top pin hole (5) is parallel to the axial direction of the camshaft (1); the elastic element is a top pin spring (6) installed in the top pin hole (5); the outer end of the top pin spring (6) abuts against the lightweight part of the swing block (32).

7. A cam pressure reduction mechanism according to claim 6, characterized in that, The top pin hole (5) is a blind hole, and the inner end of the top pin spring (6) abuts against the bottom of the blind hole.

8. A cam pressure reduction mechanism according to claim 6, characterized in that, The top pin hole (5) is a through hole, and a limit bolt (8) is installed at the other end of the through hole. The inner end of the top pin spring (6) abuts against the top of the limit bolt (8).

9. A cam pressure reduction mechanism according to claim 6, characterized in that, It also includes a return pin (7) installed in the pin hole (5); the bottom of the return pin (7) is connected to the pin spring (6), and the top is smooth and abuts against the lightweight part (32) of the throwing block.

10. A cam pressure reduction mechanism according to any one of claims 1 to 7, characterized in that, At least one of the camshaft (1) and the swivel block (3) is provided with a limiting structure to prevent the swivel block (3) from swinging beyond the limit.

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