A test method for radial force transmission characteristics of tire-rim assembly under free working conditions

Abstract

The present invention relates to the technical field of tire NVH testing, and more particularly to a method for testing the radial force transfer characteristics of a tire-rim assembly under free operating conditions. The present invention provides a method for testing the radial force transfer characteristics of a tire-rim assembly under free operating conditions. The method comprises fixing a mass block at the center of the rim and disposing an accelerometer on the mass block to obtain the rim center frequency response. Two accelerometers are disposed on the tread to calculate the average radial force transfer. The test conditions are then controlled to more accurately measure the radial force transfer characteristics of the tire-rim assembly, improve test accuracy, and enhance test stability and reliability.

Description

Technical Field

[0001] The present invention relates to the technical field of tire NVH testing, and in particular to a method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions. Background Art

[0002] Tires are the only part of a car that comes into contact with the ground. When the vehicle is driving, vibrations from the ground are transmitted into the car through the tires. The tire's ability to filter ground vibrations can be expressed by the force transferred from the tread to the center of the rim. The smaller the amplitude of the force transfer curve, the better the tire's ability to resist vibration. Therefore, the NVH performance of the tire and the vehicle can be measured by testing the force transfer characteristics of the tire and rim combination. Of the three directions, radial, lateral, and longitudinal, the radial direction has the greatest impact on vehicle vibration, and passengers are most sensitive to it. Most car companies use the radial force transfer characteristics of the tire and rim combination as one of the important criteria for determining the tire's NVH performance, and it is also one of the key references for selecting original equipment tires.

[0003] In the prior art, the invention patent (authorization announcement number: CN 105510057 B authorization announcement date: 20190101) discloses a method and device for testing wheel force transfer function in a free state, the invention patent (authorization announcement number: CN 105547715B authorization announcement date: 20180925) discloses a method for testing wheel force transfer function in a complete vehicle state, and the invention patent (authorization announcement number: CN 105675312 B Authorization Announcement Date: 20190101) discloses a method and device for testing the wheel force transfer function in a simulated whole vehicle state. However, on the tire tread, only one accelerometer is installed at the top of the tread. Due to factors such as the uniformity of the tire and the diversity of the spokes of the rim, the combination of the tire and the rim is not uniform, and the radial force transfer characteristics at different points on the tread will be different, especially the amplitude of the force transfer curve. Moreover, with the increasing number of sound-absorbing cotton tires, the difference in radial force transfer characteristics at different points on the tread of sound-absorbing cotton tires may be even greater. Therefore, if only one point is measured, the test results are likely to have large deviations, and the test accuracy and test stability need to be further improved. Summary of the Invention

[0004] To address the aforementioned technical issues, the present invention provides a method for testing the radial force transfer characteristics of a tire-rim assembly under free working conditions. This method secures a mass block at the center of the rim and arranges an accelerometer on the mass block to obtain the rim center frequency response. Two accelerometers are arranged on the tread to calculate the radial force transfer. The test conditions are then controlled to obtain more accurate and objective test results.

[0005] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions:

[0006] A method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions, the method comprising the following steps:

[0007] 1) Install the tire on the vehicle rim and adjust it to the test pressure;

[0008] 2) Glue the semicircular mass block onto the rim, with the rectangular surface of the mass block being the horizontal plane and the semicircular surface being the side surface. Apply glue to the curved edge of the side surface and adhere it to the edge of the center hole of the rim.

[0009] 3) The tire is left to stand still indoors for more than 1 hour;

[0010] 4) suspending the tire-rim assembly on a rigid support with an elastic rope;

[0011] 5) Arrange an accelerometer on the horizontal plane of the mass, located at the center of the rim, and an accelerometer above and below the tread;

[0012] 6) Use a hammer to strike the mass block in the direction perpendicular to its horizontal surface to test and automatically record the data;

[0013] 7) Data processing;

[0014] 7.1) Let the frequency response function measured at the origin of the rim be FRF center , the cross-point frequency response function of the upper tread is FRF up , the frequency response function of the lower tread cross point is FRF down , then the force transfer curve is FT=(FRF up -FRF down ) / (2*FRF center ), the tread average span frequency response function is FRF tread =(FRF up -FRF down ) / 2;

[0015] 7.2) Assume that the first-order peak value of the force transfer curve FT and its corresponding frequency are Peak 1st 、Fre 1st , the cavity peak and frequency are Peak 2nd 、Fre 2nd , the FT curve Fre obtained by the test 1st and Fre 2nd The curves nearby are smooth, without obvious jitter, and Fre 1st and Fre 2nd The test error is ±1Hz to be effective, and at least 3 valid values ​​are obtained;

[0016] 7.3) The vertical unit of the force transmission curve FT is dB. The Peak value in the measured 3rd effective value curve is selected. 1stThe curve at the middle value, if Peak 1st If there are two or more of the same, then there are the same Peak 1st In the curve, select Peak 2nd The curve at the middle value;

[0017] 7.4) Tread Frequency Response Function (FRF) tread The vertical axis unit is g / N, (m / s 2 ) / N or dB.

[0018] Preferably, in step 1), the vehicle rim is preferably a rim that is actually used. Otherwise, a rim with similar material, spokes and eccentricity is selected.

[0019] Preferably, in step 2), the semicircular mass blocks used are 20 mm thick and have radii ranging from 32 to 46 mm. The material is aluminum and the mass blocks are selected according to the size of the center hole of the rim. The surface of the mass blocks is smooth and seamlessly bonded to the rim.

[0020] Preferably, in step 3), the indoor temperature is controlled between 25±5°C.

[0021] Preferably, in step 4), the tire-rim assembly satisfies a "free-free" boundary condition when suspended.

[0022] Preferably, in step 5), the accelerometer is unidirectional or tridirectional, and its base or gasket is glued to the upper and lower centers of the tread and the center of the horizontal plane of the mass block with glue. If the upper center or the lower center of the tread happens to be a groove, the groove position is avoided. The three accelerometers are all located on the transverse center plane, and the rim valve avoids the transverse center plane, and the transverse center plane is perpendicular to the horizontal plane of the mass block.

[0023] Preferably, before testing, check whether the glue is completely dry, whether the accelerometer base or gasket is firmly attached, and whether the air pressure is accurate; the air pressure error is required to be within ±3kPa. If it exceeds this range, adjust to the test pressure and let it stand for more than 10 minutes, then retest the air pressure until the pressure meets the requirement.

[0024] Preferably, the test bandwidth is set to 1024 Hz, the resolution is set to 1 Hz or 0.5 Hz, the force signal is added with a force exponential window, the acceleration signal is added with an exponential window, and the average value of 6 taps is taken during the test.

[0025] Preferably, in step 7), within the set bandwidth, the extracted test results include the force transfer curve FT and its one-third octave curve, the first-order peak and frequency, the cavity peak and frequency, the RMS value of any frequency band, and the tread frequency response function FRF. treadIts first-order peak and frequency, cavity peak and frequency, and RMS value of any frequency band.

[0026] Furthermore, the present invention also discloses a method for testing the radial force transfer characteristics of a tire-rim assembly under free working conditions, and the method is applied in testing the radial force transfer characteristics of the tire-rim assembly.

[0027] Due to the adoption of the above technical solution, the present invention can more accurately measure the radial force transmission characteristics of the tire-rim assembly, improve the test accuracy, and enhance the stability and reliability of the test. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 Schematic diagram of the arrangement of accelerometers according to an embodiment of the present invention.

[0029] Figure 2 Schematic diagram of the dimensions of the mass block according to an embodiment of the present invention.

[0030] Figure 3 These are three valid test results of the 225 / 55R19 specification described in the embodiment of the present invention.

[0031] Figure 4 This is the 225 / 55R19 specification force transmission and its one-third octave band curve described in the embodiment of the present invention.

[0032] Figure 5 These are three valid test results for the 255 / 50R20 specification described in the embodiment of the present invention.

[0033] Figure 6 This is the 255 / 50R20 specification force transmission and its one-third octave band curve described in the embodiment of the present invention.

[0034] Figure 7 These are the results of three effective tests on the 245 / 45ZR19 sound-absorbing cotton tire described in the embodiment of the present invention.

[0035] Figure 8 This is the force transmission and one-third octave band curve of the 245 / 45ZR19 sound-absorbing cotton tire described in the embodiment of the present invention. DETAILED DESCRIPTION

[0036] The method of the invention is used for testing the radial force transmission characteristics of tire-rim assemblies of various types of tires.

[0037] The present invention is further illustrated by an example below. This example is implemented based on the technical solution of the present invention, but the scope of protection of the present invention is not limited to the following example. This example tests three sizes of tires: 225 / 55R19 and 255 / 50R20 ordinary tires and 245 / 45ZR19 sound-absorbing cotton tires.

[0038] When testing force transmission, it is difficult to directly measure the ratio of output force to input force, but it can be measured indirectly by measuring the transfer function.

[0039] Assume that the center of the rim is center, and the points above and below the tire are up and down respectively. If the point center is excited, the response of point up is a up / F center , when the point up is stimulated, the response of the point center is a center / F up , the accelerometers are arranged as follows Figure 1 shown.

[0040] According to the reciprocity principle, we can get:

[0041]

[0042] That is:

[0043]

[0044] From (2), the force transmission from the top center of the tread to the center of the rim is:

[0045]

[0046] Similarly, the force transmission from the center below the tread to the center of the rim is:

[0047]

[0048] According to (3) and (4), the average force transmission can be obtained as:

[0049]

[0050] The average cross-point frequency response of the tread is:

[0051]

[0052] The 225 / 55R19 specification was tested. The tire was installed on the vehicle rim and inflated to a test pressure of 230kPa. A semicircular mass block of appropriate size was selected. The shape of the mass block was as follows: Figure 2 As shown, fix it to the center of the rim with glue.

[0053] The tire was left to rest in the chamber for 1 hour. The tire and rim assembly was suspended from a rigid support using elastic cords, creating a "free-free" boundary condition. A unidirectional accelerometer was affixed to the center of the horizontal plane of the mass block. Two unidirectional accelerometers were placed at the center above and below the tread. All three accelerometers were located on the transverse center plane, with the rim valve positioned away from the transverse center plane, which was perpendicular to the horizontal plane of the mass block. The computer, front end, hammer, and accelerometer were connected, and the front end and computer were turned on. Upon inspection, the glue was confirmed to be completely dry, the mass block and accelerometer base were securely attached, the room temperature was 26.0°C, and the tire pressure was 231 kPa, meeting the test requirements. Open the test software, set the channel range, use a hammer to knock in the direction of the horizontal plane of the vertical mass block near the accelerometer, obtain the trigger parameters, set the bandwidth to 1024Hz, the resolution to 1Hz, the force signal plus the force exponential window, the acceleration signal plus the exponential window, set 6 averages, the amplitude is in RMS format, the test number automatically increases, the FRF estimate is Hv, automatically reject overload, monitor double clicks and automatically reject double clicks. After checking that all settings are correct, conduct the test. Take the frequency range as 25-300Hz, the frequency range of the RMS value is between 25-300Hz, the average force transfer and tread frequency response are expressed as average, the same below. The force transfer curve and tread frequency response curve of the three valid test results are as follows Figure 3 shown.

[0054] Depend on Figure 3 It can be seen that the Peak of FT above and below the tread 1st Peak 2nd There are certain differences. The first-order peak value of the tread frequency response is more obvious. The first-order peak value of the average force transfer curve FT of the three tests is 1st The results of the third test are 23.94, 24.07 and 24.05 respectively. The third test result is in the middle, so the third test is selected as the final result. The force transfer curve and its one-third octave band curve of the test results are shown in Figure 2. Figure 4 shown.

[0055] The 255 / 50R20 specification was also tested with a test pressure of 230kPa and an indoor temperature of 26.5℃. The three test results are as follows: Figure 5 shown.

[0056] Depend on Figure 5 , Peak above and below the tread 1st Peak 2nd The difference is very small, and the difference in the first-order peak of the tread frequency response can be basically ignored. It can be seen that the difference in FT above and below the tread between different tires is different. The first-order peak of the force transfer curve FT of the three tests 1stThe force transmission curve and its one-third octave band curve of the test results are shown in Figure 2. Figure 6 shown.

[0057] The sound-absorbing cotton tire with the specification of 245 / 45ZR19 was tested with the test pressure of 250kPa and the indoor temperature of 27.5℃. The results of three tests are as follows: Figure 7 shown.

[0058] Depend on Figure 7 It can be seen that the Peak of FT above and below the tread 1st Peak 2nd The difference is obvious, and the difference in the first-order peak value of the tread frequency response is also quite obvious. 1st The results of the first test are 21.77, 21.40 and 21.87 respectively. The results of the first test are in the middle, so the first test is selected as the final result. The force transmission and one-third octave band curves of the test results are shown in Figure 2. Figure 8 shown.

[0059] The above is a description of the embodiments of the present invention. The above description of the disclosed embodiments will enable professionals in the field to implement or use the present invention. Various modifications to these embodiments will be apparent to professionals in the field. The general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but should conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for testing the radial force transmission characteristics of a tire-rim assembly under free working conditions, characterized in that: The method comprises the following steps: 1) Install the tire on the vehicle rim and adjust it to the test pressure; 2) Glue the semicircular mass block onto the rim, with the rectangular surface of the mass block being the horizontal plane and the semicircular surface being the side surface. Apply glue to the curved edge of the side surface and adhere it to the edge of the center hole of the rim. 3) The tire is left to stand still indoors for more than 1 hour; 4) Hang the tire-rim assembly on a rigid support with an elastic rope; 5) Place an accelerometer on the horizontal plane of the mass, located at the center of the rim, and one accelerometer above and below the tread; 6) Use a hammer to strike the mass block perpendicular to its horizontal surface to test and automatically record the data; 7) Data processing; 7.1) Let the origin frequency response function measured at the rim center be FRF center , the cross-point frequency response function of the upper tread is FRF up , the frequency response function of the lower tread span is FRF down , then the force transfer curve is FT=(FRF up - FRF down ) / (2*FRF center ), the average cross-point frequency response function of the tread is FRF tread =(FRF up - FRF down ) / 2; 7.2) Assume that the first-order peak value of the force transfer curve FT and its corresponding frequency are Peak 1st 、Fre 1st , the cavity peak and frequency are Peak 2nd 、Fre 2nd , the FT curve Fre obtained by the test 1st and Fre 2nd The curves nearby are smooth, without obvious jitter, and Fre 1st and Fre 2nd The test error is ±1Hz to be effective, and at least 3 valid values ​​are obtained; 7.3) The vertical unit of the force transmission curve FT is dB. The Peak value in the measured 3rd effective value curve is selected. 1st The curve at the middle value, if Peak 1st If there are two or more of the same, then there are the same Peak 1st In the curve, select Peak 2nd The curve at the middle value; 7.4) Tread Frequency Response Function (FRF) tread The vertical axis unit is g / N, (m / s 2 ) / N or dB.

2. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 1), the rims used in the vehicle should be the ones that are actually used as much as possible. Otherwise, rims with similar materials, spokes, and eccentricity should be selected.

3. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 2), the semicircular mass blocks used are 20 mm thick and have a radius ranging from 32 to 46 mm. The material is aluminum and the mass blocks are selected according to the size of the center hole of the rim. The surface of the mass blocks is smooth and seamlessly bonded to the rim.

4. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 3), the indoor temperature is controlled between 25±5℃.

5. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 4), the tire-rim assembly satisfies the "free-free" boundary condition when suspended.

6. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 5), the accelerometer is unidirectional or tridirectional, and its base or gasket is glued to the upper and lower centers of the tread and the center of the horizontal plane of the mass block with glue. If the upper center or lower center of the tread happens to be a groove, the groove position is avoided. All three accelerometers are located on the transverse center plane, and the rim valve avoids the transverse center plane. The transverse center plane is perpendicular to the horizontal plane of the mass block.

7. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: Before testing, check whether the glue is completely dry, whether the accelerometer base or gasket is firmly attached, and whether the air pressure is accurate. The air pressure error is required to be within ±3kPa. If it exceeds this range, adjust it to the test pressure and let it stand for more than 10 minutes, then retest the air pressure until the pressure meets the requirement.

8. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: The test bandwidth was set to 1024 Hz, the resolution was set to 1 Hz or 0.5 Hz, the force signal was added with a force exponential window, the acceleration signal was added with an exponential window, and the average value of 6 taps was taken during the test.

9. The method for testing radial force transmission characteristics of a tire-rim assembly under free working conditions according to claim 1, characterized in that: In step 7), within the set bandwidth, the extracted test results include the force transmission rate curve FT and its one-third octave band curve, the first-order peak and frequency, the cavity peak and frequency, the RMS value of any frequency band, and the tread frequency response function FRF. tread Its first-order peak and frequency, cavity peak and frequency and RMS value of any frequency band.

10. A computer program product comprising a computer program or instructions, characterized in that When the computer program or instruction is executed by a processor, the data processing process in step 7) of the method according to any one of claims 1 to 9 is implemented.

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