Sound absorption unit, configuration method, vehicle front wall heat insulation pad and vehicle

Abstract

The invention provides a sound absorption unit and a configuration method, and relates to the technical field of noise control. Comprising a mass block, a piezoelectric plate and a rigid back plate, the mass block is vertically attached to the first surface of the piezoelectric plate, and applies pressure to the piezoelectric plate through the gravity of the mass block. The second surface of the piezoelectric plate 12 is fixed on the rigid back plate, so that the piezoelectric plate can absorb noise with a preset frequency under the pressure action of the mass block; the rigid back plate is fixed to a front wall metal plate of the vehicle and used for fixing the sound absorption unit. The noise absorption capacity of the sound absorption unit provided by the invention is mainly influenced by the rigidity of the piezoelectric plate and is not influenced by the thickness change, so that the sound absorption unit is applied to the vehicle front wall heat insulation pad by utilizing the rigid back plate, the rigid back plate can replace a heavy PU (Polyurethane) foaming plate, the noise is absorbed, particularly the noise generated by a vehicle-mounted engine is absorbed, and the noise absorption efficiency is improved. The anti-noise performance of the vehicle can be improved while the occupied space of the sound insulation material on the vehicle can be reduced, and the riding experience of a user is guaranteed.

Description

Technical Field

[0001] The present application relates to the technical field of noise control, and in particular to a sound absorbing unit, a configuration method, a vehicle front wall heat insulation pad and a vehicle. Background Art

[0002] During the operation of a vehicle, the sound generated when the vehicle engine is working is often regarded as a kind of noise. In order to ensure a good riding experience for the passengers, the prior art uses a car cowl insulation pad located between the cab and the engine compartment to isolate the noise. However, the noise reduction requirements cannot be met by relying solely on the car cowl insulation pad. On this basis, in order to improve the noise reduction performance of the car cowl insulation pad, a sound insulation layer material is generally added to the car cowl insulation pad, such as a PU (polyurethane, abbreviated as polyurethane) foam board. As the noise reduction requirements increase, the thickness of the sound insulation layer material is increased. However, the thicker sound insulation layer material occupies the use space of the vehicle, resulting in a contradiction between the noise reduction performance and the vehicle space layout. Summary of the invention

[0003] In view of this, the present application provides a sound absorbing unit, a configuration method, a vehicle front panel insulation pad and a vehicle, the main purpose of which is to solve the problem of the contradiction between noise reduction performance and spatial layout caused by laying covering materials such as PU foam boards for sound insulation at the noise prevention position of the vehicle in the prior art, such as the front panel insulation pad.

[0004] To achieve the above-mentioned purpose, the first aspect of the present application discloses a sound absorbing unit, comprising: a mass block, a piezoelectric sheet and a rigid back plate;

[0005] The mass block is vertically attached to the first surface of the piezoelectric sheet, and the mass block applies pressure to the piezoelectric sheet by its own gravity;

[0006] The second surface of the piezoelectric sheet 12 is fixed to the rigid back plate, and the piezoelectric sheet absorbs noise of a preset frequency under the pressure of the mass block;

[0007] The rigid back plate is fixed on the front panel of the vehicle.

[0008] Optionally, the sound absorbing unit further includes: a shunt circuit;

[0009] The shunt circuit is connected to the piezoelectric sheet, and is used to adjust the stiffness of the piezoelectric sheet; the shunt circuit includes a circuit whose equivalent capacitance is a negative capacitance.

[0010] Optionally, the shunt circuit includes: a first resistor, a second resistor, a third resistor, a first capacitor and an operational amplifier;

[0011] The first resistor and the first capacitor are connected in parallel to the inverting input and output of the operational amplifier, the third resistor is connected to the non-inverting input and output of the operational amplifier, the non-inverting input of the operational amplifier is connected to the first end of the second resistor, and the second end of the second resistor and the inverting input of the operational amplifier are respectively connected to the piezoelectric film.

[0012] Optionally, the shunt circuit is connected to a first surface of the piezoelectric sheet, and a second surface of the piezoelectric sheet is grounded.

[0013] Optionally, the sound absorbing unit further includes: a substrate and a cavity;

[0014] The substrate is installed between the piezoelectric sheet and the cavity, and the installation area of ​​the substrate is larger than the installation area of ​​the piezoelectric sheet;

[0015] The cavity is installed between the rigid back plate and the substrate, and is fixedly constrained to the outer edges of the rigid back plate and the substrate respectively, so as to perform spatial isolation between the rigid back plate and the substrate.

[0016] Optionally, the substrate includes: EVA material.

[0017] In a second aspect of the present application, an embodiment provides a method for configuring a sound absorbing unit, the method comprising:

[0018] Determine the sound absorption frequency of the sound absorbing unit under the test noise;

[0019] Calculating and determining a target sound absorption parameter of the sound absorption unit at the sound absorption frequency;

[0020] The stiffness of the piezoelectric sheet in the sound absorbing unit is configured according to the corresponding relationship between the target sound absorbing parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet.

[0021] Optionally, before configuring the stiffness of the piezoelectric sheet in the sound absorbing unit according to the correspondence between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet, the method further includes:

[0022] Determine the sound absorption parameters of the sound absorption unit when the piezoelectric sheet is at different stiffnesses under a preset pressure;

[0023] Determining an equivalent capacitance value of a shunt circuit according to the sound absorption parameter, wherein the shunt circuit is used to adjust the stiffness of the piezoelectric sheet;

[0024] Establishing a parameter analysis model by using the stiffness interval value of the piezoelectric sheet corresponding to the equivalent capacitance value of the shunt circuit under the preset pressure, and the corresponding relationship between the sound absorption parameter of the piezoelectric sheet and the equivalent capacitance value of the shunt circuit;

[0025] The configuring the stiffness of the piezoelectric sheet in the sound absorbing unit according to the correspondence between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet comprises:

[0026] The parameter analysis model is used to adjust the equivalent capacitance value of the shunt circuit to configure the stiffness of the piezoelectric sheet in the sound absorbing unit.

[0027] Optionally, the using the parameter analysis model to configure the stiffness of the piezoelectric sheet in the sound absorbing unit by adjusting the equivalent capacitance value of the shunt circuit includes:

[0028] Using the parameter analysis model, adjusting the resistance value of the variable resistor of the shunt circuit;

[0029] The equivalent resistance value of the shunt circuit is adjusted by using the ratio of the comparison resistor connected in series with the variable resistor to the variable resistor. The equivalent capacitance value is calculated as follows:

[0030]

[0031] Wherein, R1 is a first resistor, R2 is a second resistor, serving as a variable resistor, R3 is a third resistor, serving as a comparison resistor, and C0 is a first capacitor;

[0032] The stiffness of the piezoelectric sheet in the sound absorbing unit is configured using the adjusted shunt circuit.

[0033] Optionally, the absolute value of the equivalent capacitance of the shunt circuit is greater than the internal capacitance of the piezoelectric film.

[0034] In a third aspect of the present application, an embodiment provides a vehicle dash thermal insulation pad, on which a plurality of the sound absorbing units described in the first aspect are arranged.

[0035] In a fourth aspect embodiment of the present application, a vehicle is provided, in which the vehicle front wall insulation pad as described in the fourth aspect is installed.

[0036] The present application proposes a sound absorbing unit, including: a mass block, a piezoelectric sheet and a rigid back plate; the mass block is vertically attached to the first surface of the piezoelectric sheet, and the mass block applies pressure to the piezoelectric sheet by its own weight; the second surface of the piezoelectric sheet is fixed to the rigid back plate, and the piezoelectric sheet absorbs noise of a preset frequency under the pressure of the mass block; the rigid back plate is fixed to the front panel of the vehicle. In order to achieve the sound absorption function, the sound absorption unit disclosed in this embodiment applies pressure to the piezoelectric sheet by the gravity of the mass block itself, so that the piezoelectric sheet acts as a system similar to a spring, and can absorb noise sound waves by the piezoelectric sheet based on the rigidity of the piezoelectric sheet itself, and will not be transmitted to other positions through the sound absorption unit, thereby achieving the sound absorption function of the sound absorption unit. The noise absorption capacity of the sound-absorbing unit provided in the present application is mainly affected by the stiffness of the piezoelectric sheet and is not affected by the thickness change. Therefore, the sound-absorbing unit proposed in the present application is applied to the front insulation pad of the vehicle using a rigid back plate, which can replace the thick PU foam board to achieve noise absorption, especially the absorption of noise generated by the vehicle engine. It can reduce the occupation of the vehicle's use space by sound insulation materials, while improving the vehicle's noise resistance and ensuring the user's riding experience.

[0037] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and, together with the description, serve to explain the principles of the present application.

[0039] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0040] Figure 1 A schematic structural diagram of a sound absorbing unit provided in an embodiment of the present application is shown;

[0041] Figure 2 A shunt circuit diagram provided by an embodiment of the present application is shown;

[0042] Figure 3 A schematic structural diagram of an integral sound absorbing unit provided in an embodiment of the present application is shown;

[0043] Figure 4 A schematic flow chart of a method for configuring a sound absorbing unit provided in an embodiment of the present application is shown. DETAILED DESCRIPTION

[0044] In order to more clearly understand the above-mentioned purposes, features and advantages of the present application, the scheme of the present application will be further described below. It should be noted that the embodiments of the present application and the features in the embodiments can be combined with each other without conflict.

[0045] Among existing vehicles, the engine noise energy of large and medium-sized vehicles is mainly concentrated in the mid-frequency band of 400Hz to 2.5kHz. In order to achieve the noise reduction function, traditional noise reduction means are mainly achieved by adding sound-absorbing materials. Although this traditional method has a good control effect on mid- and high-frequency noise, the control effect on mid- and low-frequency noise is often poor. The car's front heat insulation pad is located between the cab and the engine compartment, which can isolate part of the radiation noise from the engine compartment. However, relying solely on the sound insulation of the front heat insulation pad material cannot meet the noise reduction level requirements in the car. To improve the sound insulation performance of the traditional front heat insulation pad, it is often necessary to increase the thickness of the sound insulation layer material (PU foam board), which will greatly compress the layout space of the car, which is not conducive to the layout of parts and components, and is not conducive to the development of lightweight vehicles, resulting in an irreconcilable contradiction between the NVH (Noise, Vibration, Harshness) performance of the car and the space layout and lightweight.

[0046] In order to solve the problem of the contradiction between noise reduction performance and space layout caused by laying PU foam board and other covering materials for sound insulation in the noise-proof position of the vehicle in the prior art, such as the front wall insulation pad, the present application provides the following embodiments to solve the above problems:

[0047] This embodiment provides a sound absorbing unit, such as Figure 1 As shown, it is a structural flow chart of the sound absorbing unit of this embodiment, which includes: a mass block 11, a piezoelectric sheet 12 and a rigid back plate 13;

[0048] The mass block 11 is vertically attached to the first surface of the piezoelectric sheet 12, and the mass block 11 applies pressure to the piezoelectric sheet 12 by its own gravity; the second surface of the piezoelectric sheet 12 is fixed to the rigid back plate 13, and the piezoelectric sheet 12 absorbs noise of a preset frequency under the pressure of the mass block 11; the rigid back plate 13 is fixed to the front sheet metal of the vehicle.

[0049] In the content of this embodiment, the specific structure of the sound absorbing unit is disclosed, and the specific functions of each structure thereof are disclosed. In order to achieve the absorption of noise, especially medium and low frequency noise, the content of this embodiment proposes to achieve the absorption of external noise by the piezoelectric sheet of the sound absorbing unit. Its specific working principle is that the external noise is regarded as an external stress, and the sound absorbing unit captures the external noise, which is equivalent to the stress acting on the sound absorbing unit. The mass block 11 in the sound absorbing unit is a circular metal sheet with a high density, which can provide concentrated mass, so it acts on the piezoelectric sheet 12, which is equivalent to applying a pressure to the piezoelectric sheet. Due to the material factors of the piezoelectric sheet 12, the pressure sheet 12 can be regarded as a "spring system" when the mass block applies pressure. When the external stress acts on the "spring system", the "spring system" can resolve the external stress in the piezoelectric sheet 12 through its own elastic force, which is the stiffness of the piezoelectric sheet itself, so that the sound absorbing unit can achieve the absorption of external noise. At the same time, the sound absorbing unit is fixed to the fixed position of the front panel of the vehicle by the rigid back plate, which can achieve the noise absorption of the corresponding area of ​​the fixed position, and can be used to absorb the noise of the automobile engine. On the basis that the sound-absorbing unit can be made of light and thin materials, it can replace the thick PU foam board, improve the noise resistance of the vehicle, and ensure the user's riding experience.

[0050] In a possible embodiment, the sound absorbing unit further includes: a shunt circuit;

[0051] The shunt circuit is connected to the piezoelectric sheet 12 and is used to adjust the stiffness of the piezoelectric sheet 12 ; the shunt circuit includes a circuit whose equivalent capacitance is a negative capacitance.

[0052] In the content of this embodiment, another structure of the sound absorption unit is proposed, namely, a shunt circuit. The main function of the shunt circuit is to adjust the stiffness of the piezoelectric sheet. It should be understood that the sound absorption function of the piezoelectric sheet is mainly related to its stiffness. Under noises of different frequencies, in order to ensure the sound absorption effect, piezoelectric sheets with different stiffness can be used to absorb noises of different frequencies respectively. When the noise frequency is low, its wavelength is longer, so the piezoelectric sheet with lower stiffness has a better sound absorption effect. When the noise frequency is high, its wavelength is shorter, so the piezoelectric sheet with higher stiffness has a better sound absorption effect. Based on the above correspondence, the content of this embodiment proposes to connect a shunt circuit to the periphery of the piezoelectric sheet. The shunt circuit can adjust the stiffness of the piezoelectric sheet, so that the sound absorption unit can adapt to the sound absorption function of different usage scenarios, increase the usage scenarios of the sound absorption unit, and improve the reliability of the sound absorption unit.

[0053] In this embodiment, the properties of the equivalent capacitance of the shunt circuit are further described. In order for the sound absorbing unit to fully absorb noise, the interface between the air and the sound absorbing unit must meet the zero reflection condition to achieve complete absorption of sound energy.

[0054] After connecting the shunt circuit, the sound absorption unit part is used as the acoustic part, and the shunt circuit is used as the electrical part, and the two together form an acoustic-electric coupling model. The condition for complete absorption of noise is that the input impedance of the acoustic-electric coupling model is equal to the air impedance, where the air impedance is used to represent the energy of the noise received by the surface of the piezoelectric piece. In order to achieve complete absorption of noise energy by the acoustic-electric coupling model, on the basis that the air impedance is a pure real number, when the sound absorption unit absorbs noise, the sum of the imaginary part of the equivalent capacitance value of the shunt circuit and the pure real number of the air impedance should be zero. The equivalent capacitance of the piezoelectric piece during full sound absorption is:

[0055]

[0056] In the above formula, is the mass of the mass block, C A is the stiffness of the piezoelectric film, Φ is the transformation coefficient, is the equivalent capacitance of the piezoelectric film, f is the noise frequency absorbed by the sound absorbing unit, is a variable capacitor.

[0057] This shows that choosing the right capacitor can achieve complete noise absorption. Since the value of the variable capacitor in this equation can be positive or negative, in order to ensure the accuracy of the overall circuit path, a negative capacitor needs to be introduced in the shunt circuit so that the equivalent capacitance of the final acoustic-electric coupling model can correspond to the frequency of the noise absorbed by the sound-absorbing unit.

[0058] In a possible embodiment, the shunt circuit includes: a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C0 and an operational amplifier O;

[0059] The first resistor R1 and the first capacitor C0 are connected in parallel to the inverting input and output of the operational amplifier O, the third resistor R3 is connected to the non-inverting input and output of the operational amplifier O, the non-inverting input of the operational amplifier O is connected to the first end of the second resistor R2, and the second end of the second resistor R2 and the inverting input of the operational amplifier O are respectively connected to the piezoelectric film 12.

[0060] With respect to the shunt circuit mentioned in the above embodiment, this embodiment provides a specific shunt circuit diagram, such as Figure 2As shown, a parallel RC circuit is connected between the inverting input and output of the operational amplifier. In the acoustic-electric coupling model formed by connecting the shunt circuit to the piezoelectric sheet, when the piezoelectric sheet absorbs noise, it is equivalent to an AC power supply for the shunt circuit. In the shunt circuit, by adjusting at least one of the second resistor R2 and the third resistor R3, the ratio between R2 and R3 is adjusted to change the values ​​of the positive input and the inverting input, so as to achieve the stiffness of the piezoelectric sheet adapted to the noise frequency under RC adjustment according to the output result of the output of the operational amplifier. As for the shunt circuit of this embodiment, it can essentially be understood as a negative pure capacitor and a negative pure resistor connected in parallel to the piezoelectric sheet. Therefore, in this circuit, the equivalent capacitor C ncc The calculation method is:

[0061]

[0062] In a possible embodiment, the shunt circuit is connected to a first surface of the piezoelectric piece, and a second surface of the piezoelectric piece is grounded.

[0063] In a possible embodiment, the sound absorbing unit further includes: a substrate and a cavity;

[0064] The substrate is installed between the piezoelectric sheet and the cavity, and the installation area of ​​the substrate is larger than the installation area of ​​the piezoelectric sheet; the cavity is installed between the rigid back plate and the substrate, and is fixedly constrained to the outer edges of the rigid back plate and the substrate respectively, so as to spatially isolate the rigid back plate and the substrate.

[0065] In the present embodiment, in order to further realize the absorption of noise on the basis of the piezoelectric sheet absorbing noise, the present embodiment further discloses the structure of the sound absorbing unit, including: a substrate and a cavity, and specifically discloses the connection structure of the two, such as Figure 3 The structure diagram of an integral sound absorbing unit provided by this embodiment is shown.

[0066] The substrate is a material with high elasticity. In a possible embodiment, it can be an EVA material. When the piezoelectric sheet cannot completely absorb the noise, it can rely on its own elasticity to reduce the vibration of the piezoelectric sheet caused by the noise, thereby achieving the effect of absorbing the noise.

[0067] At the same time, the sound absorbing unit of the present embodiment further includes a cavity, which is fixedly constrained to the substrate and the outer edge of the rigid back panel. The cavity relies on the vacuum inside itself to achieve noise isolation. At the same time, it and the substrate and the rigid outer edge can ensure that the noise waves transmitted from the substrate can be transmitted to the vacuum as much as possible, thereby maximizing the isolation of sound.

[0068] In this embodiment, based on the inclusion of the cavity, when calculating the equivalent capacitance in formula (1), it is necessary to further consider the stiffness of the cavity, so as to comprehensively consider the stiffness of the cavity and the stiffness of the piezoelectric sheet, and generate an equivalent stiffness that comprehensively considers the stiffness of the two. The calculation method is:

[0069]

[0070] Among them, C m is the equivalent stiffness of the sound-absorbing unit with cavity, C d A is the equivalent stiffness of the piezoelectric film, C a A is the cavity stiffness.

[0071] On the basis of further adding the cavity, the equivalent stiffness calculated by the stiffness of the cavity and the stiffness of the piezoelectric film replaces C in formula (1) A , calculate the equivalent capacitance.

[0072] On the basis of the piezoelectric sheet in the above-mentioned embodiment realizing the absorption of noise sound waves, the present embodiment further proposes to use a substrate with high elasticity and a cavity with vacuum to further enhance the sound wave absorption function of the sound absorbing unit by different noise isolation means, so that the noise absorption capacity of the sound absorbing unit is further enhanced, thereby ensuring the sound absorption effect.

[0073] The embodiment of the present application further discloses a method for configuring a sound absorbing unit, which is used to enable the sound absorbing unit to achieve an absorption effect under the action of noise of a specific frequency after the configuration is completed. The specific steps are as follows.

[0074] Step 401, determining the sound absorption frequency of the sound absorption unit under test noise.

[0075] In the process of configuring the sound absorbing unit, it is necessary to set corresponding configurations for noises of different frequencies. Therefore, in the process of configuring, it is first necessary to record the sound absorption frequency or sound absorption frequency range of the test noise absorbed by the sound absorbing unit to determine the frequency of the noise wave absorbed by the sound absorbing unit. Among them, the distance and direction between the sound absorbing unit and the test noise can be considered by those skilled in the art, so this aspect is not further limited in the content of this embodiment.

[0076] Step 402: Calculate and determine the target sound absorption parameters of the sound absorption unit at the sound absorption frequency.

[0077] In order to achieve the absorption of noise sound waves, the target sound absorption parameters required by the sound absorption unit to achieve the absorption of the sound absorption frequency need to be further confirmed according to the sound absorption frequency. Specifically, the target sound absorption parameters at least include: the mass of the mass block and the equivalent capacitance of the piezoelectric sheet. When the sound absorption unit is regarded as a "spring" system, the mass of the mass block and the equivalent capacitance of the piezoelectric sheet are respectively regarded as the "elasticity" related influencing factors of the "spring" itself.

[0078] Step 403: According to the corresponding relationship between the target sound absorption parameter of the sound absorption unit and the stiffness of the piezoelectric sheet, the stiffness of the piezoelectric sheet in the sound absorption unit is configured.

[0079] Based on the disclosure of the correlation between stiffness and noise absorption in the above embodiment, the content of this embodiment further emphasizes the need to confirm the stiffness of the piezoelectric sheet corresponding to the sound absorbing unit under the current test noise according to the correspondence between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet, so as to achieve the absorption of the test noise by the piezoelectric sheet of the sound absorbing unit.

[0080] In the present embodiment, in order to realize the configuration of the sound absorbing unit, the stiffness of the piezoelectric sheet under the best sound absorption effect for the test noise can be determined according to the correspondence between the target sound absorption parameter and the stiffness of the piezoelectric sheet, so that the sound absorbing unit can achieve the best sound absorption effect for the current test noise. On the basis that the sound absorbing unit can be made of light and thin materials, it can replace the heavy PU foam board, improve the noise resistance of the vehicle, and ensure the riding experience of the user.

[0081] In a possible embodiment, before configuring the stiffness of the piezoelectric sheet in the sound absorbing unit according to the corresponding relationship between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet, the method further includes:

[0082] Determine the sound absorption parameters of the sound absorption unit of the piezoelectric sheet at different stiffnesses under the action of a preset pressure; determine the equivalent capacitance value of the shunt circuit according to the sound absorption parameters, and the shunt circuit is used to adjust the stiffness of the piezoelectric sheet; establish a parameter analysis model using the stiffness interval value of the piezoelectric sheet corresponding to the equivalent capacitance value of the shunt circuit under the preset pressure, and the corresponding relationship between the sound absorption parameters of the piezoelectric sheet and the equivalent capacitance value of the shunt circuit;

[0083] According to the corresponding relationship between the target sound absorption parameter of the sound absorption unit and the stiffness of the piezoelectric sheet, the stiffness of the piezoelectric sheet in the sound absorption unit is configured, including:

[0084] The stiffness of the piezoelectric sheet in the sound absorbing unit is configured by adjusting the equivalent capacitance value of the shunt circuit using the parameter analysis model.

[0085] In the content of this embodiment, the corresponding relationship between the target sound absorption parameter and the stiffness of the piezoelectric sheet is further established and described. In order to achieve the absorption of noise of different frequencies, the piezoelectric sheet needs to have a stiffness corresponding to the test noise, and the sound absorption parameter corresponding to the piezoelectric sheet under this stiffness can achieve the absorption of the target noise. When the sound absorption parameter is expressed in the piezoelectric sheet, the piezoelectric sheet may present a positive equivalent capacitance. In order to adapt to the equivalent capacitance of the piezoelectric sheet, the equivalent capacitance value of the shunt circuit needs to be negative. Therefore, the shunt circuit needs to be a negative capacitance circuit. At this time, the negative capacitance circuit can be a soft circuit.

[0086] The soft negative capacitor circuit is equivalent to a negative pure capacitor Cneg and a negative pure resistor Rneg in parallel, where the negative capacitor can adjust the frequency and the negative resistor can adjust the sound absorption coefficient. By adjusting the ratio of R3 and R2, the size of the negative capacitor can be changed. In order to adapt the shunt circuit to the target sound absorption parameters, the equivalent capacitance value C can be adjusted by adjusting the ratio. ncc The negative capacitance circuit can be used to adjust the dynamic stiffness of the piezoelectric piece, according to the decrease and increase of the dynamic stiffness of the piezoelectric piece under the action of the circuit.

[0087] After establishing the corresponding relationship between the equivalent capacitance value of the shunt circuit and the corresponding stiffness interval value of the piezoelectric sheet and the sound absorption parameter of the piezoelectric sheet, a corresponding relationship between the three is established. After confirming that the equivalent capacitance value of the shunt circuit, the stiffness interval value of the piezoelectric sheet and the target sound absorption parameter of the sound absorption unit correspond to each other, a parameter analysis model is established so that any of the above parameters can be quickly checked through the model.

[0088] Therefore, in the stiffness configuration process, the corresponding relationship between the above three parameters in the parameter analysis model can be combined to quickly configure the stiffness of the piezoelectric sheet in the sound absorption unit by adjusting the equivalent capacitance value of the shunt circuit.

[0089] In a possible embodiment, the stiffness of the piezoelectric sheet in the sound absorbing unit is configured by adjusting the equivalent capacitance value of the shunt circuit using the parameter analysis model, including:

[0090] The parameter analysis model is used to adjust the resistance value of the variable resistor of the shunt circuit; the equivalent capacitance value of the shunt circuit is adjusted by using the ratio of the comparison resistor connected in series with the variable resistor to the variable resistor. The calculation method of the equivalent capacitance value is:

[0091]

[0092] Among them, R1 is the first resistor, R2 is the second resistor, which serves as a variable resistor, R3 is the third resistor, which serves as a comparison resistor, and C0 is the first capacitor; the stiffness of the piezoelectric sheet in the sound absorbing unit is configured using the adjusted shunt circuit.

[0093] In the content of this embodiment, the configuration of realizing the stiffness of the piezoelectric sheet is further explained. In order to realize the absorption of the preset frequency noise, that is, relying on the corresponding data in the parameter analysis model, the resistance value of the variable resistor of the shunt circuit is first adjusted. In the soft circuit of the above embodiment, the capacitance value Cncc of the equivalent capacitor is affected by multiple resistors. Therefore, when adjusting the equivalent capacitance value, the resistance value of the variable resistor can be adjusted. Based on the connection relationship of the resistors, the resistance ratio of the variable resistor to the comparison resistor changes accordingly. Therefore, the capacitance value of the equivalent capacitance value in the soft circuit also changes accordingly. Therefore, in the content of this embodiment, the equivalent capacitance value can be adjusted by adjusting the resistance value of the variable resistor, and further according to the change of the equivalent capacitance value, the stiffness of the piezoelectric sheet in the sound absorption unit is controlled, so as to realize the effective absorption of the corresponding frequency noise.

[0094] In a possible embodiment, the absolute value of the equivalent capacitance of the shunt circuit is greater than the internal capacitance of the piezoelectric piece.

[0095] The stability of the negative capacitance circuit is related to the piezoelectric film, which can be equivalent to a series connection of an alternating current source AC and a capacitor Cs. For a soft circuit, if the resistance part is ignored, the stability condition of the circuit is:

[0096]

[0097] That is to say, the absolute value of the equivalent capacitance Cneg of the soft circuit must be greater than the equivalent capacitance C of the piezoelectric film at the zero sound absorption frequency. b E , thereby keeping the circuit stable.

[0098] Based on this understanding, the technical solution of the present application can be embodied in the form of a software product, which can be stored in a non-volatile storage medium (which can be a CD-ROM, USB flash drive, mobile hard disk, etc.), including a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute the methods of various implementation scenarios of the present application.

[0099] By using the sound absorption unit of this embodiment, the low-frequency sound absorption capability of the car is improved while ensuring the heat insulation performance of the front heat insulation pad, replacing the heavy PU layer, and achieving the improvement of NVH performance and the lightness of the car. At the same time, by calculating and adjusting the size parameters of the mass block, the acoustic performance of the front heat insulation pad can be positively developed, which is helpful to evaluate the NVH performance and sound quality of the whole vehicle from the early stage, and reduce the frequent modification of the product in the later development.

[0100] Optionally, the above-mentioned physical device may also include a user interface, a network interface, a camera, a radio frequency (RF) circuit, a sensor, an audio circuit, a WI-FI module, etc. The user interface may include a display, an input unit such as a keyboard, etc., and the optional user interface may also include a USB interface, a card reader interface, etc. The network interface may optionally include a standard wired interface, a wireless interface (such as a WI-FI interface), etc.

[0101] The present embodiment provides a vehicle dash thermal insulation pad, on which a plurality of sound absorbing units as described in the above embodiments are arranged.

[0102] The embodiment of the present application also provides a vehicle equipped with the sound absorbing unit shown in the above embodiment. The vehicle can be a new energy vehicle or a traditional vehicle.

[0103] Through the description of the above implementation methods, the technicians in this field can clearly understand that the present application can be implemented by means of software plus the necessary general hardware platform, or by hardware. By applying the scheme of this embodiment, compared with the current prior art, this embodiment proposes a sound absorbing unit, a mass block 11, a piezoelectric sheet 12 and a rigid back plate 13; the mass block 11 is vertically attached to the first surface of the piezoelectric sheet 12, and the mass block 11 applies pressure to the piezoelectric sheet 12 by its own gravity; the second surface of the piezoelectric sheet 12 is fixed to the rigid back plate 13, and the piezoelectric sheet 12 absorbs noise of a preset frequency under the pressure of the mass block 11; the rigid back plate 13 is fixed to the front panel of the vehicle. In order to achieve the sound absorption function, the sound absorption unit disclosed in this embodiment applies pressure to the piezoelectric sheet by the gravity of the mass block itself, so that the piezoelectric sheet is a system similar to a spring, and the noise sound wave can be absorbed by the piezoelectric sheet according to the rigidity of the piezoelectric sheet itself, and will not be transmitted to other positions through the sound absorption unit, thereby achieving the sound absorption function of the sound absorption unit. The noise absorption capacity of the sound-absorbing unit provided in the present application is mainly affected by the stiffness of the piezoelectric sheet and is not affected by the thickness change. Therefore, the sound-absorbing unit proposed in the present application is applied to the front insulation pad of the vehicle using a rigid back plate, which can replace the thick PU foam board to achieve noise absorption, especially the absorption of noise generated by the vehicle engine. It can reduce the occupation of the vehicle's use space by sound insulation materials, while improving the vehicle's noise resistance and ensuring the user's riding experience.

[0104] It should be noted that, in this article, relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the term "comprises" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0105] The above is only a specific implementation of the present application, so that those skilled in the art can understand or implement the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments described herein, but will conform to the widest scope consistent with the principles and novel features applied for herein.

Claims

1. A sound absorbing unit, characterized in that: include: Mass block 11, piezoelectric sheet 12 and rigid back plate 13; The mass block 11 is vertically attached to the first surface of the piezoelectric sheet 12, and the mass block 11 applies pressure to the piezoelectric sheet 12 by its own gravity; The second surface of the piezoelectric sheet 12 is fixed to the rigid back plate 13, and the piezoelectric sheet 12 absorbs noise of a preset frequency under the pressure of the mass block 11; The rigid back plate 13 is fixed on the front panel of the vehicle.

2. The sound absorbing unit according to claim 1, characterized in that: The sound absorbing unit further comprises: a shunt circuit; The shunt circuit is connected to the piezoelectric sheet 12 , and is used to adjust the stiffness of the piezoelectric sheet 12 . The shunt circuit includes a circuit whose equivalent capacitance is a negative capacitance.

3. The sound absorbing unit according to claim 2, characterized in that: The shunt circuit comprises: a first resistor R1, a second resistor R2, a third resistor R3, a first capacitor C0 and an operational amplifier O; The first resistor R1 and the first capacitor C0 are connected in parallel to the inverting input and output of the operational amplifier O, the third resistor R3 is connected to the non-inverting input and output of the operational amplifier O, the non-inverting input of the operational amplifier O is connected to the first end of the second resistor R2, the second end of the second resistor R2 and the inverting input of the operational amplifier O are respectively connected to the piezoelectric film 12.

4. The sound absorbing unit according to claim 2, characterized in that: The shunt circuit is connected to a first surface of the piezoelectric sheet 12 , and a second surface of the piezoelectric sheet 12 is grounded.

5. The sound absorbing unit according to claim 1, characterized in that: The sound absorbing unit further comprises: a substrate and a cavity; The substrate is installed between the piezoelectric sheet 12 and the cavity, and the installation area of ​​the substrate is larger than the installation area of ​​the piezoelectric sheet; The cavity is installed between the rigid back plate 13 and the substrate, and is fixedly constrained to the outer edges of the rigid back plate and the substrate 13 respectively, so as to perform spatial isolation between the rigid back plate 13 and the substrate.

6. The sound absorbing unit according to claim 1, characterized in that: The substrate includes: a substrate made of EVA material.

7. A method for configuring a sound absorbing unit, characterized in that: include: Determine the sound absorption frequency of the sound absorbing unit under the test noise; Calculating and determining a target sound absorption parameter of the sound absorption unit at the sound absorption frequency; The stiffness of the piezoelectric sheet in the sound absorbing unit is configured according to the corresponding relationship between the target sound absorbing parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet.

8. The method according to claim 7, characterized in that Before configuring the stiffness of the piezoelectric sheet in the sound absorbing unit according to the correspondence between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet, the method further includes: Determine the sound absorption parameters of the sound absorption unit when the piezoelectric sheet is at different stiffnesses under a preset pressure; Determining an equivalent capacitance value of a shunt circuit according to the sound absorption parameter, wherein the shunt circuit is used to adjust the stiffness of the piezoelectric sheet; Establishing a parameter analysis model by using the stiffness interval value of the piezoelectric sheet corresponding to the equivalent capacitance value of the shunt circuit under the preset pressure, and the corresponding relationship between the sound absorption parameter of the piezoelectric sheet and the equivalent capacitance value of the shunt circuit; The configuring the stiffness of the piezoelectric sheet in the sound absorbing unit according to the correspondence between the target sound absorption parameter of the sound absorbing unit and the stiffness of the piezoelectric sheet comprises: The parameter analysis model is used to adjust the equivalent capacitance value of the shunt circuit to configure the stiffness of the piezoelectric sheet in the sound absorbing unit.

9. The method according to claim 8, characterized in that The method of using the parameter analysis model to configure the stiffness of the piezoelectric sheet in the sound absorbing unit by adjusting the equivalent capacitance value of the shunt circuit includes: Using the parameter analysis model, adjusting the resistance value of the variable resistor of the shunt circuit; The equivalent capacitance value of the shunt circuit is adjusted by using the ratio of the comparison resistor connected in series with the variable resistor to the variable resistor. The equivalent capacitance value is calculated as follows: Wherein, R1 is a first resistor, R2 is a second resistor, serving as a variable resistor, R3 is a third resistor, serving as a comparison resistor, and C0 is a first capacitor; The stiffness of the piezoelectric sheet in the sound absorbing unit is configured using the adjusted shunt circuit.

10. The method according to claim 8, characterized in that The absolute value of the equivalent capacitance of the shunt circuit is greater than the equivalent capacitance of the piezoelectric piece at the zero sound absorption frequency.

11. A vehicle front wall insulation pad, characterized in that: The vehicle front wall insulation pad is provided with a plurality of sound absorbing units as described in any one of claims 1 to 6.

12. A vehicle, characterized in that: The vehicle is equipped with the vehicle cowl insulation pad according to claim 11.

Images