Valve timing chain wheel narrowing structure

Abstract

The invention relates to the technical field of engines, and discloses a valve timing chain wheel narrowing structure which comprises an engine body, a chain system and a tensioning mechanism. A crankshaft output shaft used for driving is arranged in the engine body, a chain main driving wheel used for actively driving the chain system is installed at the shaft end of the crankshaft output shaft, and a chain auxiliary driving wheel used for driven driving of the chain system is arranged on one side of the chain main driving wheel. And the chain main driving wheel and the chain auxiliary driving wheel are arranged in the engine main body in an axial step dislocation and radial overlapping asymmetrical manner. The chain main driving wheel and the chain auxiliary driving wheel are arranged in the engine body in an axial step dislocation and radial overlapping asymmetrical mode, and therefore the linear thinking that the interior of a traditional horizontally-opposed motorcycle engine is limited by the space on one side corresponding to one chain wheel and the same-side space reuse concept are broken through; the two chain wheel systems share the installation area on the same side, and essential compression of the width dimension of the motorcycle engine is achieved.

Description

Technical Field

[0001] This invention relates to the field of engine technology, and in particular to a valve timing sprocket narrowing structure. Background Technology

[0002] As the core power source of a motorcycle, the engine essentially mixes air and fuel in a specific ratio through the intake system to form a combustible mixture. After compression, this mixture is ignited by the ignition system. The high-temperature, high-pressure gas generated by combustion drives the piston in reciprocating motion. This linear motion is then converted into the rotational motion of the crankshaft via the crankshaft and connecting rod mechanism. Finally, the power is transmitted to the rear wheel of the motorcycle through the transmission mechanism, enabling the vehicle to move. As the motorcycle industry develops towards high performance, lightweight, and compact designs, the structural design of the engine has an increasingly significant impact on the overall vehicle performance. This is especially true for horizontally opposed motorcycle engines, which, due to the advantages of their horizontally opposed cylinder arrangement, such as a low center of gravity and smooth operation, are widely used in mid-to-high-end cruiser motorcycles, off-road motorcycles, and sports motorcycles.

[0003] In the valve train system of a horizontally opposed motorcycle engine, the timing sprocket mechanism plays a crucial role in transmitting crankshaft power and controlling the opening and closing of the intake and exhaust valves. Its layout directly affects the engine's size, weight, reliability, and overall vehicle layout compatibility. Currently, the industry-standard dual-sided symmetrical timing sprocket layout is a mature solution based on the traditional mechanical design concept of "independent function and separate structure." Specifically, the intake camshaft sprocket and exhaust camshaft sprocket are independently arranged on the left and right sides of the engine cylinder head, respectively. Each sprocket corresponds to a complete transmission and control system, including an independent timing chain, chain tensioner, chain guide mechanism, and sealed chamber (i.e., chain chamber). This layout is technically easy to implement and initially met the needs of applications with lower requirements for engine size and overall vehicle layout. However, as motorcycles increasingly demand higher power performance, handling stability, and a compact appearance, the following drawbacks have emerged: Extremely low space utilization and excessive expansion of the engine's lateral dimensions: In the symmetrical layout, the intake and exhaust camshaft sprockets are located on opposite sides, and each chain chamber needs to form an independent enclosed space around the sprocket, resulting in a noticeable "double bulge" structure on both sides of the engine cylinder head. Because the two systems need to reserve sufficient installation clearance, chain running space, and maintenance space, the maximum lateral dimension of the engine (i.e., the distance between the outer sidewalls of the two chain chambers) far exceeds the width of the cylinder body; The system has high redundancy, but the trade-off between reliability and cost control is prominent: the dual-sided symmetrical layout requires independent timing chains, tensioners, and sealing chambers on each side of the sprocket, significantly increasing the number of system parts. Taking a twin-cylinder horizontally opposed engine as an example, compared to an integrated layout, this solution requires one more timing chain, 1-2 tensioners, 2-4 guide pulleys, and a complete sealing assembly (including end caps, sealing rings, gaskets, etc.). The tension control of the tensioners on both sides is prone to asynchrony. At high engine speeds, tension deviations may cause chain skipping, abnormal noise, or excessive wear, reducing valve timing accuracy. Simultaneously, dual-sided sealing chambers mean double the sealing interface, increasing the number of potential oil leakage points from 3-4 to 6-8. According to industry failure statistics, oil leakage failures due to chain chamber seal failure account for 15%-20% of all engine failures in engines using this layout. The overall layout of the motorcycle suffers from severe conflicts, disrupting its dynamic balance: an excessively large timing system significantly encroaches on the frame's mounting space. This is especially problematic in motorcycle frame design, where space must be reserved around the engine for the fuel tank, air filter, exhaust pipe, and braking system. The "double-bulge" structure of the chain chambers on both sides often conflicts with the layout of these components. To avoid accommodating the timing system, two compromises are typically necessary: ​​one is to raise the bottom of the fuel tank, reducing its capacity and shortening the vehicle's range; the other is to move the air filter rearward, closer to the rear wheel or under the seat, which not only increases intake drag but also alters the vehicle's weight distribution, shifting the center of gravity rearward by 5%-8%. Both raising the fuel tank and moving the air filter rearward disrupt the motorcycle's original balance, affecting its handling stability.

[0004] Therefore, a structure for narrowing the compression timing sprocket in the engine width dimension is proposed, which enables two sprocket systems to share the same mounting area through a precise spatial staggered design. Summary of the Invention

[0005] In view of the above-mentioned problems existing in the prior art, the purpose of the present invention is to provide a valve timing sprocket narrowing structure. This structure, through a precise spatial staggered design, enables two sprocket systems to share the same mounting area on the same side, thereby achieving essential compression in the engine width dimension.

[0006] This invention is achieved using the following technical solution: a valve timing sprocket narrowing structure, comprising: an engine body, a chain system, and a tensioning mechanism; The engine body has a crankshaft output shaft for driving inside. The crankshaft output shaft has a main chain drive wheel for actively driving the chain system installed at its shaft end. A secondary chain drive wheel for driven chain system is provided on one side of the main chain drive wheel. The main chain drive wheel and the secondary chain drive wheel are axially stepped and radially overlapped asymmetrically arranged inside the engine body, and a misalignment angle θ is formed between the central axes of the main chain drive wheel and the secondary chain drive wheel. The chain system includes a secondary timing sprocket and a primary timing sprocket. Timing chains are installed between the secondary timing sprocket and the secondary drive wheel of the chain, and between the primary drive wheel of the chain and the primary timing sprocket. The two sets of timing chains form a non-contact transmission channel due to the axial stepped misalignment and radial overlap of the primary drive wheel and the secondary drive wheel of the chain. The tensioning mechanism includes two sets of chain guides and two sets of tensioners. The two sets of chain guides are located on the upper side of the timing chain, and the two sets of tensioners are located on the lower side of the timing chain. The two sets of tensioners form a "Y-shaped topology".

[0007] As a further improvement to the above scheme, the misalignment angle θ between the central axes of the main drive wheel and the secondary drive wheel of the chain is in the range of 5°-20°.

[0008] As a further improvement to the above scheme, the radially overlapping tooth profiles of the main drive wheel and the secondary drive wheel of the chain overlap by 30%-50% of the tooth width on the projection plane.

[0009] As a further improvement to the above scheme, the crankshaft output shaft is arranged on the vertical central axis of the engine body.

[0010] As a further improvement to the above scheme, the axes of the secondary timing sprocket and the primary timing sprocket are on the same horizontal line.

[0011] As a further improvement to the above scheme, the tensioners of the two sets of timing chains are synchronously managed by the same motion source.

[0012] As a further improvement to the above scheme, the misalignment angle between the two sets of tensioners is the same as the misalignment angle between the main drive wheel and the secondary drive wheel of the chain.

[0013] As a further improvement to the above solution, a secondary chain chamber and a main chain chamber are respectively provided on both sides of the engine body, and the two sets of chain systems are staggered and arranged inside the secondary chain chamber and the main chain chamber.

[0014] As a further improvement to the above scheme, the side of the secondary chain chamber and the main chain chamber where the chain system is placed is a fully enclosed chain chamber.

[0015] As a further improvement to the above scheme, the secondary chain chamber and the main chain chamber are provided with side heat dissipation fin assemblies on the side opposite to the fully enclosed chain chamber.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention breaks away from the traditional linear thinking of "one sprocket corresponding to one side of space" in horizontally opposed motorcycle engines by axially staggering and radially overlapping the main drive wheel and the auxiliary drive wheel inside the engine body. It distributes the sprockets on both sides and reuses the space on the same side, allowing the two sprocket systems to share the same installation area on the same side, thus achieving a fundamental compression of the width dimension of the motorcycle engine. This invention forms a non-contact transmission channel by axial stepped misalignment and radial overlapping asymmetrical arrangement between two sets of timing chains, which can eliminate the intersection of chain running trajectories. At the same time, the radial overlapping arrangement can optimize the space utilization of the motorcycle engine. This invention uses two sets of tensioners to form a "Y-shaped topology" structure, and uses a single motion source to synchronously manage the tension force of the two chains, ensuring that the force of the two sets of tensioners pushing and pressing is balanced. This simplifies the system and improves reliability. By integrating the tensioning mechanism and reducing the number of two independent tensioners, the number of parts is reduced by 40%. This invention retains fully enclosed chain chambers on the sprocket side in both the secondary chain chamber and the main chain chamber. The single-sided sealing reduces the risk of oil leakage. Side cooling fin assemblies are arranged opposite each other in the fully enclosed chain chambers, thereby reducing the width of the secondary chain chamber and the main chain chamber compared to the width of the chain chamber of a traditional horizontally opposed motorcycle engine. This reduces the space occupied on the frame, eliminates the need to raise the fuel tank or move the air filter backward, and does not disrupt the overall balance of the vehicle. Attached Figure Description

[0017] Figure 1 This is a frontal view of the valve timing sprocket narrowing structure of the present invention; Figure 2 This is a three-dimensional perspective view of the valve timing sprocket narrowing structure of the present invention; Figure 3 This is a three-dimensional enlarged view of part A of the valve timing sprocket narrowing structure of the present invention; Figure 4 This is a diagram illustrating the chain system of the valve timing sprocket narrowing structure of the present invention; Figure 5 This is a front view of the chain system of the valve timing sprocket narrowing structure of the present invention; Figure 6 This is an enlarged view of the front view of part B of the chain system with the valve timing sprocket narrowing structure of the present invention; Figure 7 The diagram illustrates the "Y-shaped topology" structure formed by the two sets of tensioners in the valve timing sprocket narrowing structure of this invention.

[0018] Explanation of key symbols: 1. Engine body; 2. Crankshaft output shaft; 3. Main chain drive wheel; 4. Secondary chain drive wheel; 5. Secondary timing sprocket; 6. Main timing sprocket; 7. Timing chain; 8. Chain guide; 9. Tensioner; 10. Secondary chain chamber; 11. Main chain chamber; 12. Cooling fins; 13. Push rod mounting slot; 14. Hydraulic tensioner. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this disclosure clearer, the technical solutions of the embodiments of this disclosure will be clearly and completely described below with reference to the accompanying drawings.

[0020] Obviously, the described embodiments are only a part of the embodiments of this disclosure, not all of them. All other embodiments obtained by those skilled in the art based on the described embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0021] Unless otherwise defined, the technical or scientific terms used in this disclosure shall have the ordinary meaning understood by one of ordinary skill in the art to which this disclosure pertains. The terms "comprising" or "including," and similar terms used in this disclosure, mean that an element or object preceding the term encompasses the elements or objects listed following the term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "linked" are not limited to physical or mechanical connections, but may also include electrical connections, whether direct or indirect. Terms such as "upper," "lower," "left," and "right" are used only to indicate relative positional relationships; these relative positional relationships may change accordingly when the absolute position of the described objects changes.

[0022] To keep the following description of the embodiments of this disclosure clear and concise, detailed descriptions of known functions and known components are omitted.

[0023] Please combine Figure 1-7As shown, an embodiment of the present invention provides a valve timing sprocket narrowing structure, comprising: an engine body 1, a crankshaft output shaft 2 for driving is provided inside the engine body 1, and the crankshaft output shaft 2 is located on the vertical central axis of the engine body 1 (the crankshaft output shaft 2 is supported in a bearing housing by two deep groove ball bearings (model 6206), and a thrust ball bearing (model 51106) is provided in the middle of the shaft to limit axial movement), a main chain drive wheel 3 for driving the chain rotation is installed at the shaft end of the crankshaft output shaft 2 (the main chain drive wheel 3 is connected by an A-type flat key (key 10×25) and axially fixed by an M16 lock nut (with anti-loosening washer), and a secondary chain drive wheel 4 for driven chain rotation is installed on one side of the main chain drive wheel 3. Currently, horizontally opposed motorcycle engines generally adopt a double-sided symmetrical timing sprocket layout, which requires two sets of independent chains, tensioners and sealed chambers, such as Figure 4-6 As shown, by setting an axial stepped misalignment between the main drive wheel 3 and the secondary drive wheel 4 (axial stepped misalignment is a stepped offset of the axes of the main drive wheel 3 and the secondary drive wheel 4 along the crankshaft output shaft 2 by a preset distance), a misalignment angle θ is formed between the central axes of the main drive wheel 3 and the secondary drive wheel 4, and the range of the misalignment angle θ is 5°-20° (in this scheme). Figure 6 The misalignment angle θ is 12°, which results in the main drive wheel 3 and the secondary drive wheel 4 of the chain being radially overlapped and asymmetrically arranged inside the engine body 1 (radial overlap means that the main drive wheel 3 and the secondary drive wheel 4 of the chain have a partially overlapping area in the radial direction, and the overlapping area is asymmetrically distributed). Due to the asymmetrical arrangement of the radial overlap between the main drive wheel 3 and the secondary drive wheel 4 of the chain, the overlap rate of their tooth profiles on the projection plane reaches 30%-50% of the tooth width (where the misalignment angle θ is positively correlated with the overlap rate, this scheme...). Figure 6 When θ=12°, the overlap rate can reach 40%, and both the main drive wheel 3 and the secondary drive wheel 4 are made of 42CrMo chromium-molybdenum steel, with the teeth treated by high-frequency quenching and a surface hardness of HRC50-55. This breaks the traditional linear thinking that the interior of a horizontally opposed motorcycle engine is limited by "one sprocket corresponding to one side of space". The sprockets are mechanically distributed on both sides, and the concept of reusing the space on the same side is adopted. Through the precise spatial interlacing design of the main drive wheel 3 and the secondary drive wheel 4, the two sprocket systems share the same installation area on the same side, realizing the essential compression of the width dimension of the motorcycle engine. In existing horizontally opposed motorcycle engines, the timing sprockets are symmetrically positioned on both sides. At high speeds, tooth skipping on the timing sprockets can cause chain meshing interference. Figure 1-5As shown, the chain system includes a secondary timing sprocket 5 and a primary timing sprocket 6, with the axes of the secondary timing sprocket 5 and the primary timing sprocket 6 on the same horizontal line. Timing chains 7 are installed between the primary drive sprocket 3 and the primary timing sprocket 6, and between the secondary drive sprocket 4 and the secondary timing sprocket 5. (When the crankshaft output shaft 2 rotates, it drives the primary drive sprocket 3 to rotate, which in turn drives the secondary drive sprocket 4 to rotate through tooth meshing. The primary drive sprocket 3 and the secondary drive sprocket 4 use external meshing transmission with a tooth ratio of 1:1.2 and opposite transmission directions.) Simultaneously, the rotation of the primary drive sprocket 3 drives the primary timing sprocket 6 to rotate through the timing chain 7 connected to it. The rotation of the secondary drive wheel 4 drives the rotation of the secondary timing sprocket 5 via the timing chain 7 connected to it. The timing chain 7 is a roller chain with a pitch of 12.7mm, 38 teeth, and a chain plate thickness of 2.5mm. Due to the axial stepped misalignment and radial overlapping asymmetrical arrangement between the main drive wheel 3 and the secondary drive wheel 4, the two sets of timing chains 7 also have axial stepped misalignment and radial overlapping asymmetrical arrangement between the main drive wheel 3 and the secondary drive wheel 4. This creates a non-contact transmission channel between the two sets of timing chains 7, which can eliminate the intersection of chain running trajectories. At the same time, the radial overlapping arrangement can optimize the space utilization of the motorcycle engine. Traditional horizontally opposed motorcycle engines, with their dual-side layout, require independent control of the tension of two chains. The two chain systems operate independently, which can easily lead to chain interference due to asynchronous tension during high-speed engine operation. This can cause abnormal noise, additional wear, and reduce engine lifespan. Figure 1 , 2 As shown in Figures 4 and 7, a tensioning mechanism for controlling the tension of two sets of timing chains 7 is provided inside the engine body 1. The tensioning mechanism includes two sets of chain guides 8 and two sets of tensioners 9 (the tensioners 9 are made of T700 grade carbon fiber composite material with an elastic modulus of 230 GPa and a temperature range of -50℃ to 150℃, reducing weight by 30% compared to traditional steel tensioners). The two sets of chain guides 8 are located on the upper side of the two sets of timing chains 7, and the two sets of tensioners 9 are located on the lower side of the two sets of timing chains 7. The two sets of tensioners 9 form a "Y-shaped topology" structure (e.g., ...). Figure 7As shown), the two sets of tensioners 9 are driven by the same hydraulic tensioner 14 (the hydraulic tensioner 14 is installed next to the oil passage at the bottom of the engine body 1, and is connected to the two sets of tensioners 9 through a branch oil circuit. The thrust is transmitted to the swing arm of the tensioner 9 through the push rod to achieve synchronous tensioning. The hydraulic tensioner model is HT-08, with a maximum thrust of 800N and a stroke of 15mm; the diameter of the branch oil circuit oil pipe is 8mm, the oil supply pressure range is 0.3-0.5MPa, and the oil circuit has a built-in pressure relief valve (opening pressure 0.55MPa) to prevent overload. The push rod is made of 45 steel with a diameter of 10mm. The angle between the tensioner 9 and the push rod can be adaptively adjusted according to the chain tension). The two sets of timing chains 7 are pressed against the two sets of chain guides 8 by pushing their lower sides. The tension of the two chains is managed synchronously by a single motion source, which simplifies the system and improves reliability. In order to ensure that the force of the two sets of tensioners 9 is balanced, the two sets of tensioners 9 are also offset from the main drive wheel 3 and the secondary drive wheel 4 of the chain, and the offset angle is the same as that of the main drive wheel 3 and the secondary drive wheel 4 of the chain. By integrating the tensioning mechanism, two independent tensioners, four sealing gaskets and two support brackets are reduced; the chain chamber size is reduced, 12 fixing bolts and two end caps are reduced, and a total of 22 parts are reduced, achieving a 40% reduction in the number of parts. The dual-sided sealing structure of traditional horizontally opposed motorcycle engines increases the risk of oil leaks and takes up frame space, resulting in a higher center of gravity for the entire vehicle. Figure 1-2 As shown, a secondary chain chamber 10 and a main chain chamber 11 for housing the chain system are provided on both sides of the engine body 1. Due to the staggered arrangement of the two chain systems, the length of the secondary chain chamber 10 is shorter than that of the main chain chamber 11 (both the secondary chain chamber 10 and the main chain chamber 11 have push rod mounting slots 13 at the bottom for mounting the push rod of the tensioner 9). Both the secondary chain chamber 10 and the main chain chamber 11 retain fully enclosed chain chambers on the sprocket side. This single-sided sealing reduces the risk of oil leakage. Multiple sets of cooling fins 12 are arranged opposite each other in the fully enclosed chain chambers (the cooling fins 12 are wavy cooling fins, made of 6061 aluminum alloy, with a height of 18mm, a wave amplitude of 4mm, and a spacing of 9mm). The wavy heat dissipation fins are evenly distributed along the length of the chain chamber, increasing the heat dissipation area by 20% compared to traditional straight fins. Therefore, only one side needs to be arranged to meet the heat dissipation requirements, saving the space occupied by the fins on the other side. As a result of the single-sided heat dissipation fin arrangement, the width of the secondary chain chamber 10 and the main chain chamber 11 is reduced compared to the width of the chain chamber of a traditional horizontally opposed motorcycle engine. (Compared to the traditional water-cooled horizontally opposed motorcycle twin-cylinder engine of the 250c model (chain chamber width is 845mm), the width of the chain chamber in this solution is reduced to 545mm, a reduction of more than 35%). This achieves more extreme space compression, reduces the space occupied on the frame, eliminates the need to raise the fuel tank or move the air filter to the rear, and does not disrupt the overall center of gravity balance of the vehicle.

[0024] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention shall fall within the scope of protection claimed by the present invention.

Claims

1. A valve timing sprocket narrowing structure, comprising: Engine body (1), chain system and tensioning mechanism; The engine body (1) is provided with a crankshaft output shaft (2) for driving. The crankshaft output shaft (2) is equipped with a main chain drive wheel (3) for actively driving the chain system. A secondary chain drive wheel (4) for passively driving the chain system is provided on one side of the main chain drive wheel (3). The main chain drive wheel (3) and the secondary chain drive wheel (4) are axially stepped and radially overlapped asymmetrically arranged inside the engine body (1). The main chain drive wheel (3) and the secondary chain drive wheel (4) form a misalignment angle θ between their central axes. The chain system includes a secondary timing sprocket (5) and a primary timing sprocket (6). Timing chains (7) are installed between the secondary timing sprocket (5) and the secondary drive wheel (4) of the chain, and between the primary drive wheel (3) of the chain and the primary timing sprocket (6). The two sets of timing chains (7) form a non-contact transmission channel due to the axial stepped misalignment and radial overlapping asymmetrical arrangement of the primary drive wheel (3) and the secondary drive wheel (4). The tensioning mechanism includes two sets of chain guides (8) and two sets of tensioners (9). The two sets of chain guides (8) are located on the upper side of the timing chain (7), and the two sets of tensioners (9) are located on the lower side of the timing chain (7). The two sets of tensioners (9) form a "Y-shaped topology".

2. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The misalignment angle θ between the central axis of the main drive wheel (3) and the secondary drive wheel (4) of the chain ranges from 5° to 20°.

3. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The radially overlapping tooth profiles of the main drive wheel (3) and the secondary drive wheel (4) of the chain overlap on the projection plane to reach 30%-50% tooth width.

4. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The crankshaft output shaft (2) is located on the vertical center axis of the engine body (1).

5. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The secondary timing sprocket (5) and the main timing sprocket (6) are on the same horizontal line.

6. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The tensioners (9) of the two sets are synchronously managed by a single motion source for the tension of the two sets of timing chains (7).

7. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The misalignment angle between the two sets of tensioners (9) is the same as the misalignment angle between the main drive wheel (3) and the secondary drive wheel (4) of the chain.

8. The valve timing sprocket narrowing structure as described in claim 1, characterized in that, The engine body (1) has a secondary chain chamber (10) and a main chain chamber (11) on its two sides respectively, and the two sets of chain systems are staggered inside the secondary chain chamber (10) and the main chain chamber (11).

9. The valve timing sprocket narrowing structure as described in claim 8, characterized in that, The side of the secondary chain chamber (10) and the main chain chamber (11) where the chain system is placed is a fully enclosed chain chamber.

10. The valve timing sprocket narrowing structure as described in claim 9, characterized in that, The secondary chain chamber (10) and the main chain chamber (11) are provided with side heat dissipation fins (12) on the side opposite to the fully enclosed chain chamber.

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