A method for reducing noise in an automotive HVAC system

Abstract

The application discloses a kind of based on transfer function matching's automobile HVAC system noise reduction method, comprising the following steps: 1) bench restraint boundary;2) identify the noise spectrum of front-end frequency response function and near-field position of inlet and outlet water pipeline;3) identify the noise spectrum of frequency response function and near-field position of evaporator shell center point;4) identify the frequency response function of firewall sheet metal under the whole vehicle boundary;5) comparison is carried out in frequency domain, and the frequency of coupling peak value is recorded;6) identify the noise transfer function of whole vehicle boundary inlet and outlet water pipeline front end to the frequency domain based on the noise of main and vice driver's ear in vehicle;7) curve peak frequency is compared, and the frequency of coupling peak value is recorded, and the frequency of coupling peak value is avoided frequency processing.The application is a kind of HVAC assembly monomer vibration and noise transfer function test method, on the basis of existing attenuation structure, by the mode control and matching of inlet and outlet water pipeline, firewall sheet metal and HVAC shell, solve the abnormal noise problem of whole vehicle caused by vibration transmission of inlet and outlet water metal pipe.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of automotive HVAC system (hereinafter referred to as "HVAC system") NVH, and in particular to a method for solving the problem of vibration and noise transmission of the automotive HVAC system pipeline based on transfer function matching. BACKGROUND

[0002] The HVAC system is a necessary system for passenger cars, and its main function is to adjust the temperature in the car to make the driver and passenger feel more comfortable. The automotive HVAC system is usually installed on the inner side of the firewall panel. The high and low pressure metal pipes of the air conditioner pass through the firewall and are connected to the air compressor. The inlet and outlet water metal pipes of the air conditioner pass through the firewall and are connected to the water pump, which is rigidly fixed on the engine body.

[0003] To avoid the transmission of air compressor vibration to the vehicle body, a vibration isolation measure is usually added at the pipeline and the firewall panel, and the HVAC system body is not directly rigidly connected to the vehicle body panel. Since the air compressor body vibration is small, these measures can effectively block the vibration transmission and cause no NVH problem.

[0004] To reduce the transmission of engine body vibration, two structures are usually designed for vibration isolation. First, a section of rubber hose is added between the water pump and the inlet and outlet water hard pipe for vibration isolation, and then EPDM is used for vibration isolation at the firewall panel. However, due to the intense engine body vibration, the length of the hose is limited, and the water pump and water flow also have pulse excitation, so the vibration is difficult to be fully attenuated. At the same time, since the firewall panel is usually a 0.8-1.0mm thin plate and the HVAC shell is a large area thin-walled plastic, they are all easily excited to cause NVH problems.

[0005] At present, there is a lack of a method for solving the problem of idle speed noise caused by the automotive HVAC system by using transfer function matching. SUMMARY

[0006] The technical problem to be solved by the present application is to provide a method for solving the problem of vibration and noise transmission of the pipeline of the automotive HVAC system.

[0007] In order to achieve the above purpose, the technical scheme adopted by the present application is as follows: a noise reduction method for the automotive HVAC system based on transfer function matching, comprising the following steps:

[0008] 1) bench constraint boundary;

[0009] 2) identifying the frequency response function of the inlet and outlet water pipeline front end and the noise spectrum of the near field position;

[0010] 3) identifying the frequency response function of the evaporator shell center point and the noise spectrum of the near field position;

[0011] 4) Identify the frequency response function of the firewall sheet metal under the vehicle boundary;

[0012] 5) Compare the results from 2) to 4) in the frequency domain and record the frequency of the coupling peak;

[0013] 6) Identify the frequency-domain noise transfer function from the front end of the vehicle's water inlet and outlet pipes to the driver's and co-driver's ears;

[0014] 7) Compare the result in 6) with the peak frequency of the curve in 5), record the frequency of the coupling peak, and perform frequency avoidance processing on the coupling peak frequency.

[0015] The automobile HVAC system includes a water pump and an HVAC assembly. The water inlet and outlet of the water pump are connected to rubber pipes. Two of the rubber pipes are connected to one end of two metal pipes. The other ends of the metal pipes are connected to the water inlet and outlet of the HVAC assembly. The metal pipes pass through the firewall sheet metal of the automobile. The water pump is driven by the engine.

[0016] In the above 1), the HVAC assembly is elastically constrained to approximately form a free boundary constraint;

[0017] The rigid body mode of the HVAC assembly is no higher than 20 Hz.

[0018] In the above 2), two metal pipes are hammered with a 20-400 Hz pulse excitation, respectively, to identify the frequency response function of the front end of the inlet and outlet pipes and the noise spectrum at a position 5 mm away from the excitation point.

[0019] In the above 3), a 20-400 Hz pulse excitation is applied to the center point of the largest shell area at the HVAC assembly evaporator with a hammer to identify the frequency response function of the shell center point and the noise spectrum at a position 5 mm away from the excitation point.

[0020] In the above 4), the frequency response function of the firewall near the water pipe under the boundary of the vehicle is identified.

[0021] In the above 7), the method for avoiding the coupling peak frequency is as follows:

[0022] If there is a coupling peak frequency in the water inlet or outlet pipes, use some or all of the following methods to solve it:

[0023] a. Thickening of rubber pipes and metal pipe walls;

[0024] b. Changes in the diameter of rubber pipes and metal pipes;

[0025] c. Add fixing points to the HVAC housing;

[0026] d. The inlet and outlet pipes support each other;

[0027] If the frequency of the coupling peak exists in the firewall panel, the following methods are used to deal with it:

[0028] a. The firewall panel increases damping;

[0029] b. The firewall panel reduces the stiffness of the vibration isolation EPDM or increases the area to increase the attenuation;

[0030] c. The firewall panel is thickened or structurally reinforced;

[0031] If the frequency of the coupling peak exists in the HVAC assembly, the following methods are used to deal with it:

[0032] a. The shell of the HVAC assembly is locally reinforced;

[0033] b. The shell of the HVAC assembly is increased in damping material to attenuate the amplitude of vibration and noise.

[0034] In addition to the water inlet pipeline, the water outlet pipeline, the firewall panel, and the HVAC assembly in the 7), the following methods are used to deal with the frequency of the coupling peak:

[0035] a. The stiffness of the water pump connecting hose is optimized;

[0036] b. The shape of the water pump connecting pipeline is optimized.

[0037] In the 7), the parts in the automotive HVAC system are separated during processing, and the degree of separation meets the requirement of half-power bandwidth.

[0038] The present application is a test method for the vibration and noise transfer function of an HVAC assembly. Based on the existing attenuation structure, the vibration transmission caused by the vibration of the inlet and outlet metal pipes is solved by modal control and matching of the inlet and outlet pipelines, the firewall panel, and the HVAC shell. BRIEF DESCRIPTION OF DRAWINGS

[0039] The content expressed in each drawing in the specification of the present application and the marks in the drawings are briefly described as follows:

[0040] Figure 1 It is a schematic diagram of the problem model;

[0041] Figure 2 It is a schematic diagram of the problem model analysis;

[0042] The marks in the above drawings are as follows: 1, engine; 2, water pump; 3, rubber pipeline; 4, metal pipeline; 5, firewall panel; 6, HVAC assembly. DETAILED DESCRIPTION

[0043] Below, with reference to the accompanying drawings, through the description of the embodiments, the specific implementation methods of the present invention, such as the shape, structure, relative positions and connection relationships of the various components involved, the functions and working principles of the various components, the manufacturing process and operating methods, etc., are further explained in detail to help those skilled in the art to have a more complete, accurate and in-depth understanding of the inventive concept and technical solution of the present invention.

[0044] The present invention provides a method for testing the vibration and noise transfer function of an HVAC assembly 6. Based on an existing attenuation structure, the method solves the problem of abnormal vehicle noise caused by vibration transmission of the inlet and outlet water pipes by modal control and matching of the water inlet and outlet pipes, the firewall sheet metal 5, and the HVAC shell.

[0045] like Figure 1 As shown, in the environmental structure for application of the present method, there is an engine 1, a water pump 2, a rubber pipe 3, and a metal pipe 4 outside the vehicle, and an HVAC assembly 6 inside the vehicle. The inside and outside of the vehicle are separated by a firewall sheet metal 5, which also has a certain sound insulation effect. The engine 1 drives the water pump 2 to work, and the water inlet and outlet of the water pump 2 are respectively connected to two rubber pipes 3, and the two rubber pipes 3 are respectively connected to two metal pipes 4, and the other sections of the two metal pipes 4 are respectively connected to the water inlet and outlet of the HVAC assembly 6. The water pump 2 provides circulation power for the HVAC assembly 6, and the two metal pipes 4 pass through the firewall sheet metal 5 to connect the inside and outside of the vehicle.

[0046] The engine 1, water pump 2, and water pulsation are excitation sources, the rubber pipe 3 and metal pipe 4 are paths, the vibration and noise radiation of the metal pipe 4, the vibration and noise radiation of the protective wall sheet metal, and the noise radiation of the HVAC assembly 6 shell are responses. Generally speaking, the excitation source multiplied by the path equals the response. Figure 2 shown.

[0047] The noise reduction method for the automotive HVAC system based on transfer function matching specifically includes the following steps:

[0048] Step 1: The HVAC assembly 6 is approximately free and has free boundary constraints. The free boundary constraints mean that the rigid body mode of the automobile HVAC system is ensured to be no higher than 20 Hz.

[0049] Step 2: Identify the frequency response function at the front end of the inlet and outlet pipes and the noise spectrum at the near-field position. The inlet and outlet pipes are two sets of interconnected rubber pipes 3 and metal pipes 4. The identification method is to apply 20-400Hz pulse excitation to the inlet and outlet metal pipes 4 respectively with a hammer, and identify the frequency response function at the front end of the pipes and the noise spectrum at a position 5mm from the excitation point;

[0050] Step 3: Identify the frequency response function at the center of the large-surface housing of the HVAC assembly 6 and the noise spectrum at the near-field position. This identification method involves applying a 20-400 Hz pulse excitation to the center of the largest-surface housing of the HVAC assembly 6 using a hammer. The frequency response function at the center of the housing and the noise spectrum at a position 5 mm from the excitation point are then identified.

[0051] Step 4: Identify the frequency response function of the firewall under the vehicle boundary (near the water pipe position), specifically, identify the frequency response function of the firewall under the vehicle boundary (near the water pipe position) (simulation analysis results can be used in the early stage);

[0052] Step 5: Compare the results from Step 2 to Step 4 based on the frequency domain and record the frequency of the coupling peak;

[0053] Step 6: Identify the noise transfer function based on the frequency domain from the front end of the water inlet and outlet pipes at the boundary of the vehicle to the driver and co-driver's ears in the vehicle;

[0054] Step 7: Compare the result in step 6 with the peak frequency of the curve in step 5. Record the frequency of the coupling peak and perform frequency avoidance processing on the coupling peak frequency.

[0055] The specific method of avoiding the coupling peak frequency is as follows:

[0056] If there is a coupling peak frequency in the water inlet or outlet pipes, use some or all of the following methods to solve it:

[0057] a. The walls of rubber pipe 3 and metal pipe 4 are thickened;

[0058] b. The diameters of rubber pipe 3 and metal pipe 4 are changed;

[0059] c. Add fixing points to the HVAC housing;

[0060] d. The inlet and outlet pipes support each other;

[0061] If the firewall sheet metal 5 has a coupling peak frequency, use some or all of the following methods to solve it:

[0062] a. Firewall sheet metal 5 increases damping;

[0063] b. Firewall sheet metal 5 reduces the stiffness of the vibration isolation EPDM, or increases the area to increase attenuation;

[0064] c. The firewall sheet metal 5 is thickened or the structure is strengthened;

[0065] If there is a coupling peak frequency in the HVAC assembly 6, use some or all of the following methods to address it:

[0066] a. The shell of HVAC assembly 6 is partially reinforced;

[0067] b. Damping material is added to the housing of the HVAC assembly 6 to reduce vibration and noise amplitude.

[0068] For frequencies with coupling peaks in other parts (except for the water inlet pipe, water outlet pipe, firewall sheet metal 5, and HVAC assembly 6), use some or all of the following methods to address them:

[0069] a. Optimize the stiffness of the hose connecting water pump 2. Reducing the stiffness is beneficial to vibration isolation.

[0070] b. Optimize the shape of the pipe connecting water pump 2, utilize its X-axis bending stiffness, and avoid exciting the sensitive direction of the firewall.

[0071] Using the comparison method and treatment measures given in Step 7, the various modes in the vehicle HVAC system are separated. It is recommended that the degree of separation meet the half-power bandwidth requirement to resolve the abnormal vibration and noise issues of the entire vehicle caused by vibration transmission from the water inlet and outlet metal pipes.

[0072] The above steps can be performed multiple times to cyclically adjust various parts of the system until the overall preset ideal requirements are met, thereby completely resolving the idling noise problem caused by the car's HVAC system.

[0073] The present invention is described above by way of example in conjunction with the accompanying drawings. It is obvious that the specific implementation of the present invention is not limited to the above-mentioned method. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention, or the concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for reducing noise in an automobile HVAC system, characterized in that ； The engine, water pump, and water pulsation are the excitation sources, the rubber pipes and metal pipes are the paths, the metal pipe vibration and noise radiation, the protective wall sheet metal vibration and noise radiation, and the HVAC assembly shell noise radiation are the responses. The excitation source multiplied by the path equals the response. The following steps are involved: 1) Bench constraint boundary; 2) Identify the frequency response functions at the front end of the inlet and outlet pipes and the noise spectrum at the near-field position; 3) Identify the frequency response function at the center of the evaporator shell and the noise spectrum at the near-field location; 4) Identify the frequency response function of the firewall sheet metal under the vehicle boundary; 5) Compare the results from 2) to 4) in the frequency domain and record the frequency of the coupling peak; 6) Identify the frequency-domain noise transfer function from the front end of the vehicle's water inlet and outlet pipes to the driver's and co-driver's ears; 7) Compare the result in 6) with the peak frequency of the curve in 5), record the frequency of the coupling peak, and perform frequency avoidance processing on the coupling peak frequency.

2. The method for reducing noise in an automobile HVAC system according to claim 1, wherein: The automobile HVAC system includes a water pump and an HVAC assembly. The water inlet and outlet of the water pump are connected to rubber pipes. Two of the rubber pipes are connected to one end of two metal pipes. The other ends of the metal pipes are connected to the water inlet and outlet of the HVAC assembly. The metal pipes pass through the firewall sheet metal of the automobile. The water pump is driven by the engine.

3. The method for reducing noise in an automotive HVAC system according to claim 2, wherein: In the above 1), the HVAC assembly is elastically constrained to approximately form a free boundary constraint.

4. The method for reducing noise in an automotive HVAC system according to claim 3, wherein: The rigid body mode of the HVAC assembly is no higher than 20 Hz.

5. The method for reducing noise in an automobile HVAC system according to any one of claims 1 to 4, characterized in that: In the above 2), two metal pipes are hammered with a 20-400 Hz pulse excitation, respectively, to identify the frequency response function of the front end of the inlet and outlet pipes and the noise spectrum at a position 5 mm away from the excitation point.

6. The method for reducing noise in an automobile HVAC system according to claim 5, wherein: In the above 3), a 20-400 Hz pulse excitation is applied to the center point of the largest shell area at the HVAC assembly evaporator with a hammer to identify the frequency response function of the shell center point and the noise spectrum at a position 5 mm away from the excitation point.

7. The method for reducing noise in an automobile HVAC system according to claim 6, wherein: In the above 4), the frequency response function of the firewall near the water pipe under the boundary of the vehicle is identified.

8. The method for reducing noise in an automobile HVAC system according to claim 1 or 7, wherein: In the above 7), the method for avoiding the coupling peak frequency is as follows: If there is a coupling peak frequency in the water inlet or outlet pipes, use some or all of the following methods to solve it: a. Thickening of rubber pipes and metal pipe walls; b. Changes in the diameter of rubber pipes and metal pipes; c. Add fixing points to the HVAC housing; d. The inlet and outlet pipes support each other; If there are coupling peak frequencies on the firewall sheet metal, use some or all of the following methods: a. Increase damping of firewall sheet metal; b. Reduce the stiffness of the EPDM insulation of the firewall sheet metal, or increase the area to increase attenuation; c. Thicken the firewall sheet metal or strengthen the structure; If the HVAC assembly has coupling peak frequencies, use some or all of the following methods: a. Local reinforcement of the HVAC assembly shell; b. Add damping material to the HVAC assembly housing to reduce vibration and noise amplitude.

9. The method for reducing noise in an automobile HVAC system according to claim 8, wherein: In 7), except for the water inlet pipe, water outlet pipe, firewall sheet metal, and HVAC assembly, the frequencies with coupling peaks are processed using some or all of the following methods: a. Optimize the stiffness of the water pump connecting hose; b. Optimize the shape of the water pump connecting pipe.

10. The method for reducing noise in an automobile HVAC system according to claim 9, wherein: In the above 7), the various parts of the automobile HVAC system are separated during processing, and the degree of separation meets the requirements of half-power bandwidth.

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