Method for solving rough sound of engine balance shaft

Abstract

The application provides a method for solving rough sound of an engine balance shaft, comprising the following steps: S1, performing NVH test on the engine to determine the approximate position of the rough sound source; S2, designing a cylinder cut-off test and canceling a balance shaft test for the engine to be tested to determine that the rough sound is caused by torsional vibration excitation; S3, establishing a CAE simulation analysis model capable of viewing torsional vibration of each position of a crankshaft, and using the established CAE simulation analysis model to perform cylinder cut-off simulation analysis on the engine to be tested to determine the influence of cylinder cut-off of each cylinder of the engine to be tested on the balance shaft excitation; and S4, replacing the installation position of the balance shaft on the crankshaft of the engine to be tested, and using the CAE simulation analysis model to analyze the rough sound of the balance shaft installed at different positions to determine the optimal installation position of the balance shaft which can generate the optimal rough sound.

Description

Technical Field

[0001] This invention belongs to the field of automotive NVH (Noise, Vibration, Harshness), specifically relating to a method for solving the rough noise of an engine with a balance shaft. Background Technology

[0002] With the rapid development of the automotive industry, users are increasingly emphasizing the perceived quality of products. The industry has begun to shift from the most basic stage of automotive NVH control—the traditional "vibration reduction and noise reduction"—to "sound quality control." Automotive sound quality has become a crucial indicator for evaluating vehicle performance. One of the most prominent complaints from customers regarding excessive acceleration noise is the roughness of engine operation, which can give the impression of a stiff and dry engine. Current technologies typically involve adding sound insulation and vibration damping devices along the transmission path, but these methods are costly and cannot completely solve the sound quality problem.

[0003] When an engine is running, the reciprocating motion of the piston within the cylinder generates significant reciprocating inertial forces on the piston and connecting rod, causing engine vibration and reducing comfort. This is more pronounced in high-powered engines. To balance the second-order reciprocating inertial forces generated by the piston's motion, current technology typically involves installing a balance shaft on the engine that rotates eccentrically and synchronously with the crankshaft. This balances the inertial forces generated by the piston's motion and reduces engine vibration. However, the addition of a balance shaft often introduces coarse noise that affects the perceived quality. The coarse noise generated by the balance shaft has a high frequency, and the effectiveness of vibration absorbers along the transmission path is limited. Furthermore, sound-absorbing materials are expensive. Therefore, there is an urgent need for a method to control the coarse noise from the balance shaft at its source. Summary of the Invention

[0004] This invention provides a method to reduce excitation and solve the problem of rough sound at its source, thereby reducing the cost of the whole vehicle and improving sound quality.

[0005] To achieve the above objectives, the present invention provides a method for effectively solving the rough noise of balance shafts at its source by combining experimentation and simulation. The method specifically includes the following steps:

[0006] This invention provides a method for solving the rough noise of an engine balance shaft, comprising:

[0007] Step S1: Perform NVH testing on the engine to determine the approximate location of the source of the rough noise.

[0008] Step S2 involves designing a cylinder deactivation test and a balance shaft cancellation test for the engine under test to determine that the rough sound originates from the crankshaft torsional vibration excitation of the balance shaft.

[0009] Step S3: Establish a CAE simulation analysis model that can view the torsional vibration at each position of the crankshaft, and use the established CAE simulation analysis model to design a cylinder cut-off test for the engine under test, and determine the influence of cylinder cut-off of each cylinder of the engine under test on the torsional vibration at the balance shaft installation position.

[0010] Step S4: Change the installation position of the balance shaft on the crankshaft of the engine under test, and use the CAE simulation analysis model to analyze the rough sound at different installation positions of the balance shaft in order to determine the optimal installation position of the balance shaft that produces the best rough sound.

[0011] Preferably, the method further includes:

[0012] Step S5: Based on the optimal installation position of the balance shaft obtained from simulation analysis, a sample of the balance shaft installed at the optimal installation position is made, and then the sample is subjected to NVH testing on a test bench. After the sample passes the NVH test on the test bench, the engine optimized according to the sample is installed in the vehicle for NVH verification.

[0013] Preferably, step S1 includes:

[0014] Step S11: Arrange triaxial vibration sensors at the cylinder block positions corresponding to each cylinder of the engine under test, arrange triaxial vibration sensors on the cylinder head of the engine under test, arrange triaxial vibration sensors at the front and rear positions of the oil pan, arrange microphone sensors at predetermined distances above and below the engine under test, and arrange torsional vibration sensors at the crankshaft hub and ring ends of the engine under test respectively.

[0015] Step S12: Perform NVH testing on the test bench under the condition where the engine under test has the most severe rough noise, and obtain vibration data, noise data and torsional vibration data.

[0016] Step S13: Compare the noise characteristics of the rough sound of the engine under test in the whole vehicle state with the noise characteristics of the rough sound of the engine under test in the bench state. Perform coherent analysis between the microphone sensor signal and the vibration sensor signal at each location to determine the vibration signal with the greatest correlation to the rough sound, so as to determine the approximate location of the source of the rough sound.

[0017] Preferably, step S2 includes:

[0018] Step S21: Sequentially cut off the fuel supply to each cylinder of the engine under test. After cutting off the fuel supply to each cylinder, repeat steps S12 and S13 to determine the effect of each cylinder of the engine under test on the rough sound.

[0019] Step S22: Remove the balance shaft of the engine under test, and repeat steps S12 and S13 to determine the effect of the balance shaft of the engine under test on the rough sound.

[0020] Step S23: Based on the influence of each cylinder of the engine under test on the rough sound and the influence of the balance shaft of the engine under test on the rough sound, the excitation source most related to the rough sound is determined to be torsional vibration excitation.

[0021] Preferably, step S3 includes:

[0022] Step S31: Establish a CAE simulation analysis model that allows viewing of torsional vibrations at various positions of the crankshaft;

[0023] Step S32: Use the NVH torsional vibration test data obtained in step S12 to calibrate the CAE simulation analysis model;

[0024] Step S33: Using the calibrated CAE simulation analysis model, cylinder failure tests are performed sequentially on each cylinder of the engine under test to determine the impact of cylinder failure on the excitation of the balance shaft.

[0025] Preferably, step S4 includes:

[0026] Step S41: Analyze the torsional vibration level of the crankshaft at various positions under full-load acceleration conditions using a CAE simulation analysis model.

[0027] Step S42: Based on the analysis results of step S41, compare and analyze the torsional vibration levels of the balance shaft installed between cylinders 1 / 2 and 3 / 4 to obtain the optimal installation position of the balance shaft.

[0028] The beneficial effects of this invention are as follows:

[0029] By analyzing the correlation between vibration and noise signals, the approximate location of the rough sound is quickly determined, reducing the difficulty of problem analysis. Suspected components are replaced and analyzed to further pinpoint the source of the rough sound. Based on the characteristics of the rough sound, i.e., the impact of load on the rough sound, corresponding cylinder deactivation tests are designed to further identify influencing factors. A combination of experimental and simulation methods is used to further clarify the influence mechanism of these factors on the rough sound. A model distinct from traditional analysis is established, allowing for the observation of torsional vibration at various crankshaft positions, providing a basis for exploring solutions. Simulation methods are used to quickly develop optimization schemes, reducing the cycle and cost of prototype manufacturing, rapidly verifying effects and achieving engineering feasibility, and ultimately achieving optimal NVH performance. Attached Figure Description

[0030] Figure 1 This is a flowchart of the coarse sound control method provided in this embodiment;

[0031] Figure 2 This is a flowchart of the objective NVH test provided in this embodiment;

[0032] Figure 3 This is a schematic diagram of the NVH objective test sensor arrangement provided in this embodiment;

[0033] Figure 4 This is a schematic diagram of the engine bench rough acoustic modulation analysis provided in this embodiment;

[0034] Figure 5 This is a flowchart illustrating the operation of the cylinder failure and balance shaft cancellation test provided in this embodiment;

[0035] Figure 6 This is a schematic diagram of the modulation results after sequentially cutting off the fuel supply to each cylinder, as provided in this embodiment.

[0036] Figure 7 This is a schematic diagram of the modulation analysis of oil pan vibration before and after removing the balance shaft, provided in this embodiment.

[0037] Figure 8 This is a flowchart of the CAE simulation analysis provided in this embodiment;

[0038] Figure 9 This is a schematic diagram of the analysis model provided in this embodiment, which allows viewing the torsional vibration levels of various parts of the crankshaft system;

[0039] Figure 10 This is a schematic diagram of the torsional vibration results at the balance shaft position after canceling the cylinder pressure of each cylinder, provided in this embodiment.

[0040] Figure 11 This is a schematic diagram showing the angular acceleration results at the balance shaft position after sequentially canceling the cylinder pressure of each cylinder, as provided in this embodiment.

[0041] Figure 12 This embodiment provides a flowchart for the simulation analysis of the optimal installation position of the balance shaft.

[0042] Figure 13 This is a schematic diagram of the torsional mode shape of the crankshaft system provided in this embodiment;

[0043] Figure 14 This is a schematic diagram of the torsional vibration results at various locations of the crankshaft system provided in this embodiment;

[0044] Figure 15 This is a schematic diagram showing the comparison results of torsional vibration at different installation positions of the balance shaft provided in this embodiment.

[0045] Figure 16 A flowchart for verifying the optimization scheme provided in this embodiment;

[0046] Figure 17 This is a schematic diagram of the modulation spectrum of the optimized vibration at the front position of the oil pan provided in this embodiment;

[0047] Figure 18 This is a schematic diagram showing the comparison of the rough sound of the whole vehicle before and after optimization in this embodiment. Detailed Implementation

[0048] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings and the description of the preferred embodiments:

[0049] like Figure 1 The diagram shown is a flowchart of a coarse sound control method provided in an embodiment of the present invention. The method is as follows:

[0050] S1, such as Figure 3 As shown, 10 vibration sensors are placed in key engine locations such as the engine block, cylinder head, and oil pan. Figure 3 The ten locations marked 3, 4, 7, 8, 9, 10, 12, 13, 14, and 15 are used to place two microphones on the upper and lower parts of the engine. Figure 3 (The locations marked 11 and 5) are where torsional vibration sensors are placed at the crankshaft hub and ring end. Figure 3 The engine's rough noise was most pronounced at two locations (marked as 1 and 2) on the crankshaft 6. Coherence analysis was then used to determine the approximate location of the source of the rough noise.

[0051] S2. Based on the overall vehicle performance, design a cylinder failure verification to determine the impact of each cylinder's operation on the rough sound, design a verification to eliminate the balance shaft, and clarify the relationship between crankshaft torsional vibration and the change in rough sound.

[0052] S3. Establish a CAE simulation analysis model that can view the torsional vibration at each position of the crankshaft. Based on the experiment, calibrate the CAE simulation analysis model to ensure its reliability. Analyze the impact of cylinder failure on torsional vibration and determine the impact of cylinder failure on the excitation of the balance shaft.

[0053] S4. Explore the location with smaller torsional vibration excitation. Based on the analysis results, change the installation position of the balance shaft on the crankshaft, conduct simulation analysis, obtain the scheme with the smallest balance shaft response, and then obtain the theoretical optimal installation position of the balance shaft.

[0054] S5. Based on the simulation analysis scheme, verify the physical scheme and promote the engineering implementation.

[0055] like Figure 2 The diagram shown is a flowchart of the objective NVH test in this embodiment, which includes the following steps:

[0056] S11, such as Figure 3 The diagram shows the arrangement of NVH objective test sensors, which includes four cylinder block three-dimensional vibration sensors, four cylinder head three-dimensional vibration sensors, two oil pan front and rear three-dimensional vibration sensors, one microphone sensor at the top and bottom of the engine (25cm), and one crankshaft hub / ring end torsional vibration sensor.

[0057] S12. Conduct NVH (noise, vibration and harshness) tests to evaluate the roughness of the vehicle and determine the operating condition with the most severe engine roughness, namely the full-load acceleration condition. Perform NVH and torsional vibration tests on the test bench for this condition.

[0058] Three test groups were conducted, with the acceleration rate controlled to be the same as that of the complete vehicle, in order to reproduce the state of the complete vehicle.

[0059] S13. Extract the noise characteristics of rough sound under the whole vehicle condition, compare it with the noise characteristics under the test bench condition, and perform coherence analysis between the test bench microphone signal and the vibration sensor signal at each position to determine which vibration signal has the greatest correlation with the rough sound, so as to determine the approximate location where the rough sound is generated.

[0060] Since the engine under test in this embodiment is a 4-cylinder engine, and the rough sound is generated by 0.5-order modulation, the 0.5-order modulation depth is used in this embodiment to evaluate the intensity of the rough sound, such as... Figure 4 The results are the modulation analysis of the rough sound from the engine test bench, with the 0.5th order modulation being the strongest.

[0061] Analysis revealed that the vibration in front of the oil pan of the engine under test was most correlated with the rough sound, and the approximate location of the rough sound was initially determined to be the crankshaft, balance shaft or timing system in front of the oil pan.

[0062] like Figure 5 The diagram shown is an operation flowchart for performing cylinder deactivation and balance shaft removal tests on the engine under test in this embodiment, which specifically includes the following steps:

[0063] S21. Design a cylinder cut-off test for the engine under test. Cut off the fuel supply to each cylinder of the engine under test in sequence, and repeat the operations in S11 and S12 to determine the effect of the power output of each cylinder on the rough sound.

[0064] NVH testing of the engine under test in a fully functional vehicle revealed that the harsh noise is related to the load; the greater the load, the more pronounced the harsh noise. After each cylinder's fuel supply is cut off, that cylinder does no work, reducing its excitation to the crankshaft. This further confirms that the lower the load, the less pronounced the harsh noise.

[0065] like Figure 6 The diagram shows the modulation of vibration in front of the oil pan after each cylinder is sequentially cut off from the oil supply. The results show that after cutting off the first cylinder, the 0.5-order modulation depth is significantly reduced, and the harsh sound is also significantly reduced to an indistinguishable level. After cutting off the second, third, and fourth cylinders, the modulation depth does not change significantly. This indicates a strong correlation between the excitation of the first cylinder and the harsh sound.

[0066] S22. Remove the balance shaft of the engine under test and repeat the NVH tests in S11 and S12. Modulate and analyze the vibration of the oil pan to determine the influence of the balance shaft on the rough sound.

[0067] like Figure 7 The diagram shows the modulation analysis of the vibration of the oil pan before and after the balance shaft was removed. After the balance shaft was removed, the 0.5-order modulation depth was significantly reduced and basically undetectable, indicating that the rough sound was strongly correlated with the balance shaft.

[0068] S23. Conduct a detailed analysis of the above vibration, noise, and torsional vibration test data to clarify the relationship between crankshaft torsional vibration and rough sound.

[0069] Since the rough noise disappeared after the balance shaft was removed, the hardware influence of the oil pump and timing system was ruled out, and the analysis was focused on the crankshaft and balance shaft system.

[0070] Based on the sensitivity analysis of engine torsional vibration, torsional vibration is related to engine cylinder pressure. After fuel cut-off, cylinder pressure decreases, engine load decreases, and torsional vibration also weakens significantly, indicating that torsional vibration is the main excitation source of rough sound.

[0071] like Figure 8 The diagram shown is a flowchart of the CAE simulation analysis operation in this embodiment, which includes the following steps:

[0072] S31. Establish a CAE simulation analysis model that can view the torsional vibration at various positions of the crankshaft system in order to theoretically verify the above experiments.

[0073] Traditional torsional vibration analysis models can only assess the torsional vibration levels at the front and rear ends. However, the rough noise is caused by the crankshaft exciting the balance shaft, requiring analysis of the balance shaft's installation position. Therefore, a CAE simulation analysis model suitable for this invention needs to be established, such as... Figure 9 The image shows a CAE simulation analysis model that allows you to view the torsional vibration levels at various locations in the crankshaft system.

[0074] S32. Apply torsional vibration test data to calibrate the CAE simulation analysis model to ensure the reliability of the simulation results.

[0075] To better apply the simulation analysis results to the formulation of solutions, the CAE simulation analysis model needs to be calibrated using the torsional vibration test results in S1 to ensure the effectiveness of the analysis results and improve the efficiency of problem solving.

[0076] S33. Perform cylinder failure analysis on each cylinder separately to determine the impact of cylinder failure on the excitation of the balance shaft.

[0077] like Figure 10 This diagram illustrates the torsional vibration at the balance shaft location after sequentially canceling cylinder compression. Canceling each cylinder reduces the resonance band at the balance shaft mounting location. Stopping one cylinder has the greatest impact on the torsional vibration at the balance shaft mounting location, with the impact decreasing sequentially, and stopping four cylinders having the least impact.

[0078] like Figure 11This diagram illustrates the angular acceleration results at the balance shaft location after sequentially canceling cylinder compression. Canceling any cylinder will cause a decrease in the amplitude of each order and the overall amplitude at the balance shaft mounting location. Stopping one cylinder has the greatest impact on torsional vibration at the balance shaft mounting location, with the impact decreasing sequentially, and stopping four cylinders having the least impact.

[0079] The above analysis shows that only by reducing the cylinder pressure of cylinder 1, i.e., the cylinder corresponding to the balance shaft, can the excitation at the balance shaft mounting position be reduced. However, the torsional vibration sensitivity analysis results indicate that torsional vibration is related to the structure and cylinder pressure, with cylinder pressure affecting dynamic performance. Therefore, structural optimization is necessary.

[0080] like Figure 12 The diagram shown is a simulation analysis flowchart of the optimal installation position of the balance shaft in this embodiment, which includes the following steps:

[0081] S41. Analyze the torsional vibration level at various positions of the crankshaft under full-load acceleration conditions using CAE simulation analysis models to provide a basis for mechanism optimization.

[0082] like Figure 13 This is a schematic diagram of the torsional mode vibration of the crankshaft system. Generally, the amplitude decreases as you get closer to the rear end of the crankshaft. The amplitude is smallest at the position of the 4th cylinder, and the amplitudes at the positions before and after it are also small. The amplitude is largest at the ring at the TVD end.

[0083] like Figure 14 The results represent the torsional vibration at various locations in the crankshaft system; the torsional vibration decreases towards the rear of the crankshaft.

[0084] S42. Based on the analysis results of S41, the torsional vibration levels of the balance shaft installed between cylinders 1 / 2 and 3 / 4 are compared and analyzed to obtain the theoretical optimal installation position of the balance shaft.

[0085] like Figure 15 To compare the results, the balance shaft was moved to the rear, and its amplitude was significantly reduced. The amplitude was reduced by more than 50% when it was moved from the front to the rear. The balance shaft was positioned between the 3rd and 4th cylinders with little difference from the rear of the crankshaft. Considering other requirements, the optimal position for the balance shaft of this engine is between the 3rd and 4th cylinders.

[0086] like Figure 16 The flowchart shown is the verification process for the optimization scheme in this embodiment, which includes the following steps:

[0087] S51. Based on the above simulation analysis results, a prototype with the balance shaft installed between the 3 / 4 cylinders is manufactured.

[0088] S52. NVH test under S12 conditions was conducted on the test bench to obtain a comparison of the rough sound before and after optimization. The modulation sense was significantly reduced after optimization.

[0089] like Figure 17To optimize the modulation spectrum of the vibration at the front position of the oil pan, the 0.5-order modulation depth was significantly reduced.

[0090] S53. Install the optimized engine in the vehicle and conduct NVH verification, such as... Figure 18 To optimize the contrast between the rough sound before and after, and to meet the requirements.

[0091] The beneficial effects of the method for solving the rough noise of the engine balance shaft provided in this embodiment are as follows: By analyzing the correlation between vibration and noise signals, the approximate location of the rough noise can be quickly determined, reducing the difficulty of problem analysis; suspected parts are replaced and analyzed to further pinpoint the source of the noise; based on the manifestation of the rough noise, i.e. the influence of load on the rough noise, corresponding cylinder deactivation tests are designed to further pinpoint the influencing factors; by combining experimental and simulation methods, the influence mechanism of influencing factors on the rough noise is further clarified; a model different from traditional analysis is established, which can view the torsional vibration at various positions of the crankshaft, providing a basis for exploring solutions; simulation methods are used to quickly formulate optimization solutions, reducing the cycle and cost of prototype production, quickly verifying the effect and realizing engineering, and achieving optimal NVH effect.

Claims

1. A method for solving the rough noise of an engine balance shaft, characterized in that, include: Step S1: Perform NVH testing on the engine to determine the approximate location of the source of the rough sound. Step S2 involves designing a cylinder deactivation test and a balance shaft cancellation test for the engine under test to determine that the rough sound originates from the crankshaft torsional vibration excitation of the balance shaft. Step S3: Establish a CAE simulation analysis model that can view the torsional vibration at each position of the crankshaft, and use the established CAE simulation analysis model to analyze the cylinder failure of the engine under test, and determine the impact of cylinder failure of each cylinder of the engine under test on the torsional vibration of the balance shaft installation position. Step S4: Change the installation position of the balance shaft on the crankshaft of the engine under test, and use the CAE simulation analysis model to analyze the rough sound at different installation positions of the balance shaft in order to determine the optimal installation position of the balance shaft that produces the best rough sound. Step S4 includes: Step S41, using a CAE simulation analysis model to analyze the torsional vibration level at various positions of the crankshaft of the engine under test under full-load acceleration conditions; Step S42: Based on the analysis results of step S41, compare and analyze the torsional vibration levels of the balance shaft installed between cylinders 1 / 2 and 3 / 4 to obtain the optimal installation position of the balance shaft. The optimal level of rough sound refers to the state in which the modulation depth of the 0.5th order noise generated by the crankshaft torsional vibration excitation of the balance shaft is reduced to the lowest level.

2. The method for solving the rough noise of the engine balance shaft according to claim 1, characterized in that, The method further includes: Step S5: Based on the optimal installation position of the balance shaft obtained from simulation analysis, a sample of the balance shaft installed at the optimal installation position is made, and then the sample is subjected to NVH testing on a test bench. After the sample passes the NVH test on the test bench, the engine optimized according to the sample is installed in the vehicle for NVH verification.

3. The method for solving the rough noise of the engine balance shaft according to claim 2, characterized in that, Step S1 includes: Step S11: Arrange triaxial vibration sensors at the cylinder block positions corresponding to each cylinder of the engine under test, arrange triaxial vibration sensors on the cylinder head of the engine under test, arrange triaxial vibration sensors at the front and rear positions of the oil pan, arrange microphone sensors at predetermined distances above and below the engine under test, and arrange torsional vibration sensors at the crankshaft hub and ring ends of the engine under test respectively. Step S12: Perform NVH testing on the test bench under the condition where the engine under test has the most severe rough noise, and obtain vibration data, noise data and torsional vibration data. Step S13: Compare the noise characteristics of the rough sound of the engine under test in the whole vehicle state with the noise characteristics of the rough sound of the engine under test in the bench state. Perform coherent analysis between the microphone sensor signal and the vibration sensor signal at each location to determine the vibration signal with the greatest correlation to the rough sound, so as to determine the approximate location of the source of the rough sound.

4. The method for solving the rough noise of the engine balance shaft according to claim 3, characterized in that, Step S2 includes: Step S21: Cut off the fuel supply to each cylinder of the engine under test in sequence. After cutting off the fuel supply to each cylinder, repeat steps S12 and S13 to determine the effect of combustion excitation of each cylinder of the engine under test on the rough sound. Step S22: Remove the balance shaft of the engine under test, and repeat steps S12 and S13 to determine the effect of the balance shaft of the engine under test on the rough sound. Step S23: Based on the influence of each cylinder of the engine under test on the rough sound and the influence of the balance shaft of the engine under test on the rough sound, the excitation source most related to the rough sound is determined to be crankshaft torsional vibration, which excites the balance shaft and thus generates rough sound.

5. The method for solving the rough noise of the engine balance shaft according to claim 4, characterized in that, Step S3 includes: Step S31: Establish a CAE simulation analysis model that allows viewing of torsional vibrations at various positions of the crankshaft; Step S32: Use the NVH torsional vibration test data obtained in step S12 to calibrate the CAE simulation analysis model; Step S33: Using the calibrated CAE simulation analysis model, cylinder failure analysis is performed sequentially on each cylinder of the engine under test to determine the impact of cylinder failure on the torsional vibration excitation of the balance shaft position.

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