A low-noise engine gear transmission system suitable for commercial vehicles

Abstract

This utility model discloses a low-noise engine gear transmission system suitable for commercial vehicles, with the crankshaft timing gear as the power input end; the large idler gear of the upper gear train is located in the upper left corner of the crankshaft timing gear and meshes with it; the air compressor gear is located in the lower left corner of the large idler gear and meshes with it, and the indirect transmission speed ratio between the air compressor gear and the crankshaft timing gear is 1.5; the oil pump gear is located in the right side of the crankshaft timing gear and meshes with it; the lower gear train includes a lower transmission idler gear, a camshaft idler gear I, a camshaft idler gear II, and a camshaft timing gear; the lower transmission idler gear is located below the large idler gear and is coaxial with it; the camshaft idler gear I is located in the upper right corner of the lower transmission idler gear and meshes with it; the camshaft idler gear II is located above the camshaft idler gear I and meshes with it; the camshaft timing gear is located in the upper left corner of the camshaft idler gear II and meshes with it.

Description

Technical Field

[0001] This utility model relates to the field of engine technology, and in particular to a low-noise engine gear transmission system suitable for commercial vehicles. Background Technology

[0002] Passengers in commercial vehicles spend long periods inside the vehicle, creating a high demand for overall vehicle noise control. Given a fixed vehicle structure, the engine gear transmission system is the core factor influencing overall vehicle noise. The spatial arrangement of the gear train and the matching of key gear ratios directly determine meshing smoothness and noise release levels. Current commercial vehicle engine gear transmission systems exhibit significant design shortcomings: the upper and lower layer layouts often only consider installation space adaptation, neglecting the isolation of fluctuating loads and precision loads, as well as the rationality of power transmission paths. This leads to the superposition of vibrations from fluctuating load components such as the upper air compressor and precision load components such as the lower valve train, easily causing component interference. Furthermore, the transmission ratio between the air compressor gear and the crankshaft timing gear is only aimed at meeting the basic power supply speed of the air compressor, without optimization for noise control, failing to establish the necessary load-speed coordination for noise reduction. These deficiencies make uneven meshing forces prone to occur in the gear transmission, with air compressor vibration directly transmitted to the entire gear train, becoming the main noise source. This reduces passenger comfort and accelerates tooth surface wear and shortens gear train life due to unstable forces.

[0003] Existing technologies often improve noise by replacing sound insulation materials and increasing gear hardness, but they have significant limitations: sound insulation materials can only passively reduce noise transmission and cannot eliminate noise causes caused by unreasonable layout and mismatched speed ratios; increasing gear hardness will increase production and maintenance costs and cannot solve the core problems of vibration superposition and meshing instability. Neither of these can meet the long-term use requirements of commercial vehicles for low noise, high reliability and low cost.

[0004] The above background information is provided only to aid in understanding the concept and technical solution of this utility model. It does not necessarily belong to the prior art of this patent application. In the absence of clear evidence that the above information was disclosed on the filing date of this patent application, the above background information should not be used to evaluate the novelty and inventiveness of this application. Utility Model Content

[0005] The purpose of this invention is to propose a low-noise engine gear transmission system suitable for commercial vehicles, in order to solve the technical problems of superimposed gear system vibration, large meshing noise, and easy wear of components in the prior art.

[0006] Therefore, this utility model proposes a low-noise engine gear transmission system suitable for commercial vehicles.

[0007] Preferably, the present invention may also have the following technical features:

[0008] A low-noise engine gear transmission system suitable for commercial vehicles, with crankshaft timing gear as the power input end, includes an upper gear train and a lower gear train;

[0009] The upper gear train includes a crankshaft timing gear, a large idler gear, an air compressor gear, and an oil pump gear; the large idler gear is located in the upper left corner of the crankshaft timing gear and meshes with it; the air compressor gear is located in the lower left corner of the large idler gear and meshes with it, and the indirect transmission speed ratio between the air compressor gear and the crankshaft timing gear is 1.5; the oil pump gear is located in the right side region of the crankshaft timing gear and meshes with it.

[0010] The lower gear train includes a lower drive idler gear, a camshaft idler gear I, a camshaft idler gear II, and a camshaft timing gear. The lower drive idler gear is located below the large idler gear and is coaxially arranged with it. The camshaft idler gear I is located in the upper right region of the lower drive idler gear and meshes with it. The camshaft idler gear II is located above the camshaft idler gear I and meshes with it. The camshaft timing gear is located in the upper left region of the camshaft idler gear II and meshes with it.

[0011] Preferably, the crankshaft timing gear, large idler gear, air compressor gear, oil pump gear, lower transmission idler gear, camshaft idler gear I, camshaft idler gear II, and camshaft timing gear all adopt helical gear structure to improve transmission smoothness and reduce noise.

[0012] Preferably, the helix angle of the upper gear train is adapted to the vibration reduction requirements of the fluctuating load of the air compressor; the helix angle of the lower gear train is adapted to the transmission accuracy requirements of the air distribution system; and a preset axial distance is provided between the upper and lower gear trains to block the vibration transmission between the upper and lower gear trains.

[0013] Preferably, the meshing overlap ratio between the air compressor gear and the large idler gear is 1.3 to 1.8 to improve meshing smoothness under fluctuating loads.

[0014] Preferably, the spokes of the large idler gear are provided with a lightweight structure to reduce rotational inertia and reduce vibration excitation.

[0015] Preferably, the pitch circle diameter of the oil pump gear is matched with the pitch circle diameter of the crankshaft timing gear to meet the transmission requirements of the preset operating speed of the oil pump.

[0016] Preferably, the axial assembly clearance between the lower drive idler gear and the large idler gear is less than 0.03 mm, and the two are interference-fitted to ensure the stability of synchronous rotation.

[0017] Preferably, the meshing backlash between the camshaft idler gear I and the camshaft idler gear II is 0.02~0.05mm, so as to reduce the transmission vibration noise of the lower gear train.

[0018] The beneficial effects of this utility model compared with the prior art include:

[0019] 1. This utility model adopts a layered layout of "upper gear train bearing the fluctuating load of air compressor / oil pump, and lower gear train dedicated to driving camshaft valve train mechanism". With the coaxial fixed structure of large idler gear and lower transmission idler gear, the periodic fluctuating load of air compressor is strictly limited to the upper layer from the structural level, blocking its transmission to the lower precision valve train system. This avoids the fluctuating load from interfering with the accuracy of valve timing and ensures the accurate opening and closing timing of engine valves. At the same time, it constructs a clear power transmission path of "crankshaft → large idler gear → upper and lower gear trains", avoiding the shaking and jamming problems of traditional messy layouts, and improving the smoothness of gear train operation and the synchronization of power transmission.

[0020] 2. This utility model specifically designs an indirect transmission speed ratio of 1.5 between the air compressor gear and the crankshaft timing gear, which enables the air compressor load torque curve and the crankshaft speed fluctuation curve to form a stable periodic correspondence, providing a feasible structural premise for load phase adjustment (a non-1.5 speed ratio cannot form this stable correspondence and does not have phase adjustability); based on this, gear knocking noise can be eliminated by adjusting the air compressor gear phase, solving the pain point that the existing technology cannot specifically eliminate this noise.

[0021] 3. Based on the upper gear train layout and 1.5 speed ratio design, the air compressor gear can directly transmit power to the crankshaft timing gear through the large idler gear, eliminating the need for the air compressor idler gear required in the lower layer of the existing technology. This not only reduces the noise source of a pair of gear meshing pairs, but also reduces the production cost of gear processing and assembly; at the same time, it reduces the number of core transmission components and the weight of the whole machine, meeting the engineering requirements of lightweight and low cost of operating vehicles.

[0022] 4. The structural optimization of this application does not require the addition of additional noise reduction devices. It can continuously reduce noise under the long-term and continuous operation of the vehicle by simply adjusting the gear parameters and layout, thereby improving the driving environment for the driver. Attached Figure Description

[0023] Figure 1 This is a structural schematic diagram of a specific embodiment of the present utility model.

[0024] Figure 2This is a load torque curve of the air compressor gear phase advance by 15 teeth according to this utility model.

[0025] Figure 3 This is a load torque curve of the air compressor gear phase advance of 17 teeth according to this utility model.

[0026] Explanation of reference numerals in the attached diagram: 1-Crankshaft timing gear; 2-Large idler gear; 3-Air compressor gear; 4-Oil pump gear; 5-Camshaft idler gear I; 6-Camshaft idler gear II; 7-Camshaft timing gear. Detailed Implementation

[0027] The present invention will now be described in further detail with reference to specific embodiments and the accompanying drawings. It should be emphasized that the following description is merely exemplary and is not intended to limit the scope and application of the present invention.

[0028] Non-limiting and non-exclusive embodiments will be described with reference to the following figures, wherein the same reference numerals denote the same parts unless otherwise specifically stated.

[0029] This embodiment discloses a low-noise engine gear transmission system suitable for commercial vehicles, such as... Figure 1 As shown, with crankshaft timing gear 1 as the power input end, its core is to achieve low-noise transmission through gear train layout optimization and gear parameter adjustment, specifically including upper gear train and lower gear train.

[0030] Specifically, the upper gear train includes a crankshaft timing gear 1, a large idler gear 2, an air compressor gear 3, and an oil pump gear 4; the large idler gear 2 is located in the upper left corner of the crankshaft timing gear 1 and meshes with the crankshaft timing gear 1; the air compressor gear 3 is located in the lower left corner of the large idler gear 2 and meshes with the large idler gear 2, and the indirect transmission speed ratio between the air compressor gear 3 and the crankshaft timing gear 1 is 1.5; the oil pump gear 4 is located in the right side of the crankshaft timing gear 1 and meshes with the crankshaft timing gear 1.

[0031] The lower gear train includes a lower drive idler gear (not shown in the figure), a camshaft idler gear I5, a camshaft idler gear II6, and a camshaft timing gear 7. The lower drive idler gear is located below the large idler gear 2 and is coaxially arranged with the large idler gear 2. The two are fixedly connected to achieve synchronous rotation. The coaxial fixed connection between the large idler gear 2 and the lower drive idler gear adopts a combination of a flat key and an interference fit. The flat key is used to transmit torque, and the interference fit is used to ensure coaxiality and avoid eccentric vibration during power transmission. The camshaft idler gear I5 is located in the upper right region of the lower drive idler gear and meshes with the lower drive idler gear. The camshaft idler gear II6 is located above the camshaft idler gear I5 and meshes with the camshaft idler gear I5. The camshaft timing gear 7 is located in the upper left region of the camshaft idler gear II6 and meshes with the camshaft idler gear II6. The gears of the upper and lower gear trains are arranged in the same gear chamber, which is made of cast iron and has a sound-absorbing coating on the inner wall to further reduce noise radiation.

[0032] This embodiment further specifies that the crankshaft timing gear 1, large idler gear 2, air compressor gear 3, oil pump gear 4, lower transmission idler gear, camshaft idler gear I5, camshaft idler gear II6, and camshaft timing gear 7 all adopt helical gear structures to improve transmission smoothness and reduce noise. The tooth surfaces of all the above gears are carburized and quenched, achieving a tooth surface hardness of 58-62 HRC and a core hardness of 30-35 HRC, balancing tooth surface wear resistance and core toughness to meet the long-term, high-load operating requirements of commercial vehicles. Helical gears have helical tooth surfaces, and the meshing process is a progressive line contact. Compared with the instantaneous surface contact of spur gears, the meshing impact is smaller, and the vibration and noise during transmission are significantly reduced. Helical gears have a higher overlap ratio and more tooth pairs participating in meshing at the same time, resulting in a more uniform load distribution and the ability to withstand greater impact loads. This solves the problem of gear impact fatigue when operating vehicles frequently start and stop. The tooth surface contact stress during helical gear meshing is smaller, reducing the probability of failure modes such as pitting and spalling.

[0033] This embodiment further specifies that the helix angle of the upper gear train is adapted to the vibration reduction requirements of the fluctuating load of the air compressor; the helix angle of the lower gear train is adapted to the transmission accuracy requirements of the air distribution system; and a preset axial distance is provided between the upper and lower gear trains to block the vibration transmission between them. The helix angle of the upper gear train ranges from 15° to 20°, preferably 18°; the helix angle of the lower gear train ranges from 8° to 12°, preferably 10°. The preset axial distance between the upper and lower gear trains is 15-20mm, which is limited by the stepped structure of the gear chamber seat to ensure assembly accuracy. The differentiated design of the helix angle needs to be matched with the opposite rotation direction of the gears. The upper gear train uses left-hand helical gears, and the lower gear train uses right-hand helical gears. The axial forces generated by the two are in opposite directions and can cancel each other out, reducing the axial load on the bearings. The upper gear train features a large helix angle of 15°-20°, further enhancing gear meshing overlap and effectively absorbing the impact vibrations from the periodic fluctuating loads of the air compressor, preventing vibration transmission to the engine block and thus reducing overall engine noise. The lower gear train's small helix angle of 8°-12° ensures smooth transmission while reducing axial forces generated by gear meshing, preventing axial movement from affecting valve timing accuracy and ensuring precise valve opening and closing. The 15-20mm axial spacing between the upper and lower gear trains, combined with the reinforcing ribs of the gear housing, cuts off the vibration transmission path between them, preventing the vibrations from the upper fluctuating load from being amplified by the vibrations from the lower valve train, further reducing overall engine vibration and noise. The reverse helix direction of the upper and lower gears offsets most of the axial force, reducing the axial load pressure on the bearings by more than 50%, extending bearing life, and lowering the engine failure rate.

[0034] This embodiment further specifies that the meshing overlap ratio between the air compressor gear 3 and the large idler gear 2 is 1.3~1.8 to improve meshing smoothness under fluctuating loads. An overlap ratio of 1.3-1.8 means that during gear transmission, an average of 1.3-1.8 pairs of teeth simultaneously engage, distributing the load across multiple pairs of teeth. This reduces the load-bearing pressure on a single pair of teeth by 30%-50%, avoiding meshing impact noise caused by single-tooth overload. Under conditions of rapid changes in air compressor load (such as acceleration and braking of operating vehicles), the high overlap ratio of the gear meshing pair can effectively buffer load impacts, preventing instantaneous overload on the tooth surface and reducing the gear wear rate. The design of multiple teeth meshing simultaneously averages the periodic impact noise of gear meshing, reducing the peak meshing noise by 3-5 dB(A), thus improving the driving comfort of operating vehicles.

[0035] This embodiment further specifies that the spokes of the large idler gear 2 are provided with a lightweight structure to reduce rotational inertia and vibration excitation. The lightweight structure can be a series of circular through holes evenly distributed along the circumference of the spokes of the large idler gear 2; the number and diameter of the through holes can be set according to requirements. This structure reduces power loss during engine startup and improves the engine's startup response speed, making it particularly suitable for the frequent start-stop conditions of commercial vehicles.

[0036] This embodiment further specifies that the pitch circle diameter of the oil pump gear 4 is matched with the pitch circle diameter of the crankshaft timing gear 1 to meet the transmission requirements of the preset operating speed of the oil pump. Taking the air compressor gear 3 with 38 teeth as an example, with an indirect transmission ratio of 1.5, the number of teeth on the crankshaft timing gear 1 can be deduced to be 57, and its pitch circle diameter is 2.5 × 57 = 142.5 mm. The oil pump gear 4 directly meshes with the crankshaft timing gear 1. To ensure stable lubrication pressure under all engine operating conditions, the preset operating speed of the oil pump is 1.1 to 1.3 times the crankshaft speed. Therefore, the oil pump gear 4 is designed with 48 teeth and a pitch circle diameter of 2.5 × 48 = 120 mm to ensure the transmission ratio meets lubrication requirements. Through precise matching of the pitch circle diameter, the oil pump speed and crankshaft speed maintain an optimal matching relationship, ensuring stable oil supply pressure under all operating conditions from engine idle speed to rated speed, avoiding problems of excessively high or low oil pressure.

[0037] In this embodiment, the transmission ratio between the air compressor gear 3 and the crankshaft timing gear 1 is set to 1.5 (achieved by the air compressor gear having 38 teeth, a module of 3.0023mm, and a pitch circle diameter of 114.087mm, where 114.087mm = 3.0023mm × 38 teeth). This is a key optimization design for achieving low-noise transmission. The specific principle and verification are as follows:

[0038] At this transmission ratio of 1.5, the air compressor load torque curve and the crankshaft speed fluctuation curve form a stable periodic correspondence, providing a basis for adjusting the load phase of air compressor gear 3. If a transmission ratio other than 1.5 is used, the two cannot form a stable periodic correspondence, the load phase is in a state of disordered fluctuation, lacks phase adjustment adjustability, and cannot eliminate gear knocking noise. Through load torque testing on the shaft behind air compressor gear 3, it can be seen that: the downward peak of the load torque curve corresponds to abnormal knocking action of the gear, which will generate obvious additional transmission noise; the remaining smooth torque fluctuations are the forces of normal gear meshing and will not generate additional noise.

[0039] Load phase adjustment is achieved by adapting the locating pin holes of the air compressor gear 3 and the drive shaft. Multiple sets of locating pin holes with different angles are set on the connection end face between the gear hub and the drive shaft. By selecting different combinations of pin holes, the phase offset of the air compressor gear 3 relative to the large idler gear 2 can be achieved (e.g., advancing by 15 teeth, 17 teeth, etc.), with a positioning accuracy of ±0.5 teeth, ensuring accurate phase adjustment. Load torque testing uses a strain gauge torque sensor, attached to the drive shaft behind the air compressor gear 3, to collect real-time load torque fluctuation data under different operating conditions. The testing accuracy meets the requirements for noise correlation analysis.

[0040] Typical operating condition verification results: such as Figure 2 As shown, under the engine operating condition of 1300r / min (corresponding to urban congestion driving conditions), the red curve in the figure is the torque curve of 0 phase (without adjusting the load phase) with a speed ratio of 1.5. There is a significant downward peak, which corresponds to abnormal gear knocking action and generates significant additional transmission noise. After advancing the air compressor gear 3 phase by 15 teeth, the downward peak completely disappears, and the gear knocking noise is eliminated, as shown by the blue curve in the figure.

[0041] like Figure 3 As shown, under the engine operating condition of 1700r / min (corresponding to high-speed cruising), the red curve in the figure is the torque curve of 0 phase at a speed ratio of 1.5, which has a significant downward peak, corresponding to gear knocking noise; after advancing the 3rd phase of the air compressor gear by 17 teeth, the downward peak completely disappears, corresponding to the blue curve in the figure, and the gear knocking noise is eliminated.

[0042] The 1.5 gear ratio is not a conventional parameter selection, but rather a prerequisite for achieving load phase adjustment. It solves the problem of existing technologies being unable to specifically eliminate gear knocking noise caused by air compressor load. Phase adjustment specifically eliminates gear knocking noise under core operating conditions, which is one of the main noise sources in the gear transmission system of commercial vehicle engines. Noise reduction significantly improves driving comfort. After phase adjustment, the load torque curve becomes flatter, the instantaneous impact load on a single pair of gear teeth is greatly reduced, tooth surface impact wear is reduced, gear life is extended, and it is suitable for the high-load operating conditions of commercial vehicles with frequent start-stop cycles.

[0043] This embodiment further specifies that the axial assembly clearance between the lower drive idler gear and the large idler gear 2 is less than 0.03mm, and the two adopt an interference fit to ensure the stability of synchronous rotation, avoid axial movement between the lower drive idler gear and the large idler gear 2, and ensure the synchronous rotation accuracy of the two. The combination of flat key and interference fit can effectively transmit the engine torque. The interference fit can further avoid problems such as keyway wear and slippage that may occur with key connections, improving the reliability of the transmission system. The design without axial movement avoids impact friction between the gear end face and the bearing, reduces axial vibration noise, and further improves the low noise performance of the whole machine.

[0044] This embodiment further specifies that the meshing backlash between the camshaft idler gear I5 and the camshaft idler gear II6 is 0.02~0.05mm, in order to reduce the transmission vibration noise of the lower gear train. This can effectively compensate for the thermal expansion of the gears during engine operation, while accommodating the machining and assembly errors of the gears, avoiding gear seizing or jamming problems, and further reducing meshing knocking noise.

[0045] Those skilled in the art will recognize that numerous variations are possible with respect to the above description, and the embodiments and figures are merely for describing one or more specific implementations.

[0046] Although exemplary embodiments of the present invention have been described and illustrated, those skilled in the art will understand that various changes and substitutions can be made thereto without departing from the spirit of the present invention. Furthermore, many modifications can be made to adapt specific situations to the doctrine of the present invention without departing from the central concept of the present invention described herein. Therefore, the present invention is not limited to the specific embodiments disclosed herein, but may include all embodiments and equivalents that fall within the scope of the present invention.

Claims

1. A low-noise engine gear transmission system suitable for commercial vehicles, using a crankshaft timing gear as the power input end, characterized in that, Including the upper gear train and the lower gear train; The upper gear train includes a crankshaft timing gear, a large idler gear, an air compressor gear, and an oil pump gear; the large idler gear is located in the upper left corner of the crankshaft timing gear and meshes with it; the air compressor gear is located in the lower left corner of the large idler gear and meshes with it, and the indirect transmission speed ratio between the air compressor gear and the crankshaft timing gear is 1.5; the oil pump gear is located in the right side region of the crankshaft timing gear and meshes with it. The lower gear train includes a lower drive idler gear, a camshaft idler gear I, a camshaft idler gear II, and a camshaft timing gear. The lower drive idler gear is located below the large idler gear and is coaxially arranged with it. The camshaft idler gear I is located in the upper right region of the lower drive idler gear and meshes with it. The camshaft idler gear II is located above the camshaft idler gear I and meshes with it. The camshaft timing gear is located in the upper left region of the camshaft idler gear II and meshes with it.

2. The low-noise engine gear transmission system for commercial vehicles according to claim 1, characterized in that, The crankshaft timing gear, large idler gear, air compressor gear, oil pump gear, lower drive idler gear, camshaft idler gear I, camshaft idler gear II, and camshaft timing gear all adopt helical gear structure to improve transmission smoothness and reduce noise.

3. The low-noise engine gear transmission system for commercial vehicles according to claim 2, characterized in that, The helix angle of the upper gear train is adapted to the vibration reduction requirements of the fluctuating load of the air compressor; the helix angle of the lower gear train is adapted to the transmission accuracy requirements of the air distribution system; and a preset axial distance is provided between the upper and lower gear trains to block the vibration transmission between the upper and lower gear trains.

4. The low-noise engine gear transmission system for commercial vehicles according to claim 2, characterized in that, The meshing overlap ratio between the air compressor gear and the large idler gear is 1.3~1.8 to improve meshing smoothness under fluctuating loads.

5. The low-noise engine gear transmission system for commercial vehicles according to claim 1, characterized in that, The large idler gear has a lightweight structure at its spokes to reduce rotational inertia and vibration excitation.

6. The low-noise engine gear transmission system for commercial vehicles according to claim 1, characterized in that, The pitch circle diameter of the oil pump gear is matched with the pitch circle diameter of the crankshaft timing gear to meet the transmission requirements of the preset operating speed of the oil pump.

7. The low-noise engine gear transmission system for commercial vehicles according to claim 1, characterized in that, The axial assembly clearance between the lower drive idler gear and the large idler gear is less than 0.03 mm, and the two adopt an interference fit to ensure the stability of synchronous rotation.

8. The low-noise engine gear transmission system for commercial vehicles according to claim 1, characterized in that, The meshing backlash between the camshaft idler gear I and the camshaft idler gear II is 0.02~0.05mm, in order to reduce the transmission vibration and noise of the lower gear train.

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