Noise evaluation method for rubber piece, and noise evaluation device for rubber piece

Abstract

To provide a noise evaluation method for a rubber piece and the like that can easily and accurately evaluate slide noise, and can reduce the labor in conducting a test and test cost.SOLUTION: A noise evaluation method for a rubber piece 5 includes the steps of: fixing an accelerometer 35 to a rubber piece 5; bringing an outer surface of the rubber piece 5 into contact with a pseudo road surface 30a, with the rubber piece 5 making swing displacement including translational displacement and circular displacement with respect to the pseudo road surface 30a, and collecting output data from the accelerometer 35 in a data collection period including at least part of a contact period during which the rubber piece 5 and the pseudo road surface 30a are in contact with each other; conducting frequency analysis of data based on the output data in the data collection period; and evaluating noise on the basis of frequency analysis data obtained from the frequency analysis.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a method and an apparatus for evaluating noise of a rubber piece. [Background technology]

[0002] A conventional tire noise measuring method is described in Patent Document 1. This tire noise measuring method measures tire noise by using a sound level measuring device to measure tire noise generated by running a tire in contact with a rotating drum having a simulated road surface on its outer circumferential surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-134213 A Summary of the Invention [Problem to be solved by the invention]

[0004] It is known that tire noise increases during acceleration when a driving force is applied. It is also said that the contribution of block sliding noise to noise that increases with acceleration is large. Therefore, in order to improve the reduction of noise that increases with acceleration, it is necessary to evaluate the sliding noise. However, the method of Patent Document 1 also measures sounds other than the sliding noise, such as air column resonance sound and block collision sound, making it difficult to evaluate the sliding noise, and therefore the noise that increases with acceleration.

[0005] Furthermore, in the method of Patent Document 1, tire noise generated by running a tire in contact with a rotating drum having a simulated road surface on its outer periphery is measured with a noise meter. Therefore, when conducting the test, test tires must be prepared, which increases the labor and testing costs required for the test.

[0006] Therefore, an object of the present disclosure is to provide a method and device for evaluating noise of a rubber piece that makes it easy to accurately evaluate sliding noise and reduces the labor and testing costs required for testing. [Means for solving the problem]

[0007] In order to solve the above problems, the noise evaluation method for a rubber piece according to the present disclosure includes the steps of fixing an accelerometer to a rubber piece, contacting the outer surface of the rubber piece with a pseudo road surface while the rubber piece undergoes a swing displacement including a translational displacement and a circular displacement relative to the pseudo road surface, and collecting output data from the accelerometer during a data collection period that includes at least a portion of the contact period during which the rubber piece is in contact with the pseudo road surface, performing frequency analysis on data based on the output data during the data collection period, and evaluating noise based on the frequency analysis data obtained by the frequency analysis.

[0008] According to the present disclosure, a noise test is performed by contacting a simulated road surface with a rubber piece while simultaneously displacing (moving in a translational direction) and displacing (moving in a circular arc), so that the rubber piece can be moved in the same manner as the movement of the outer peripheral surface of an actual tire, making it possible to perform an accurate noise test, and the translational displacement can cause the rubber piece to slip, making it easy to accurately evaluate the slipping noise. Also, according to the present disclosure, the test is performed using only the rubber piece, and there is no need to create a test tire, so the labor and testing costs involved in the test can be reduced.

[0009] In addition, the data collection period may be a period from a start timing defined by the timing at which the contact pressure of the rubber piece against the simulated road surface becomes maximum, or a start timing defined by the timing after which the rubber piece is in contact with the simulated road surface, to an end timing after the start timing when the rubber piece is positioned at a distance from the simulated road surface.

[0010] According to this configuration, the slipping noise caused by the stick-snap phenomenon can be accurately evaluated.

[0011] The data collection period may be included in a period from a first time when the front of the rubber piece comes into contact with the simulated road surface to a second time when the front of the rubber piece leaves the simulated road surface.

[0012] According to this configuration, it is possible to accurately evaluate the slipping noise caused by the stick-slip phenomenon.

[0013] Furthermore, noise may be evaluated based on data in the range of 500 Hz to 3000 Hz among the frequency analysis data obtained by the frequency analysis.

[0014] According to this configuration, it is easy to accurately evaluate noise caused by slipping.

[0015] The noise may also be evaluated by comparing data based on the frequency analysis data with a threshold value.

[0016] According to this configuration, noise caused by slippage can be easily evaluated objectively and accurately using a simple method.

[0017] In addition, the rubber piece noise evaluation device according to the present disclosure includes an accelerometer fixed to the rubber piece, an actuator that causes the rubber piece to perform a swing displacement including a translational displacement and an arcuate displacement relative to a pseudo road surface, and the pseudo road surface in contact with the rubber piece for at least a portion of the period during which the rubber piece performs the swing displacement.

[0018] According to the present disclosure, a noise test can be performed by contacting a simulated road surface with a rubber piece in a translational displacement and a circular arc at the same time. Therefore, the rubber piece can be moved in the same manner as the movement of the outer circumferential surface of an actual tire, making it possible to perform a noise test accurately, and the translational displacement can cause the rubber piece to slip, making it easy to accurately evaluate the slipping noise. Furthermore, according to the present disclosure, the test can be performed using only the rubber piece, and there is no need to prepare a test tire, so the labor and testing costs involved in the test can be reduced.

[0019] The vehicle may also include a period identification unit that identifies a data collection period that includes at least a portion of a contact period during which the rubber piece and the pseudo road surface are in contact with each other, a frequency analysis unit that performs frequency analysis on data based on output data from an accelerometer during the data collection period, and a noise evaluation unit that evaluates noise based on the frequency analysis data frequency analyzed by the frequency analysis unit.

[0020] According to this configuration, it is easy to evaluate the slippage noise with high accuracy. Effect of the Invention

[0021] The rubber piece noise evaluation method and rubber piece noise evaluation device according to the present disclosure make it easy to accurately evaluate sliding noise, and can reduce the effort and testing costs required for testing. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a side view of a rubber piece noise evaluation device according to an embodiment of the present disclosure, as viewed from the side. [Diagram 2] FIG. 2 is a diagram illustrating slip noise in tire noise. [Diagram 3] This is a graph obtained by a noise evaluation device, and shows the relationship between vibration data in dB obtained by applying a fast Fourier transform to data based on signals from an accelerometer when a slip ratio, i.e., the magnitude of slippage, is set, and the vibration frequency, comparing a case where the slip ratio is 0% with a case where the slip ratio is 4%. [Figure 4] This is a graph obtained by a noise evaluation device, which shows the relationship between vibration data dB obtained by applying a fast Fourier transform to data based on signals from an accelerometer, and the vibration frequency, comparing the case where the slip ratio is 0% with the case where the slip ratio is 9%. [Diagram 5] 1 is a graph showing the relationship between A-weighted sound pressure level dB and frequency in a tire noise evaluation test on a vehicle equipped with tires. [Figure 6]13 is a graph showing the relationship between A-weighted sound pressure level dB and frequency in a tire noise evaluation test for a vehicle equipped with a different tire. [Figure 7] 1 is a graph showing an example of test results of a noise evaluation device, illustrating the relationship between acceleration level and slip ratio. [Figure 8] 13 is a graph showing other test results of the noise evaluation device, and is a graph showing the relationship between acceleration level and slip ratio. [Figure 9] FIG. 13 is a side view of the modified rubber piece noise evaluation device as viewed from the side. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, the embodiments according to the present disclosure will be described in detail with reference to the accompanying drawings. In addition, when multiple embodiments or modified examples are included below, it is assumed from the beginning that new embodiments will be constructed by appropriately combining the characteristic parts of those. In addition, in the following examples, the same components are given the same symbols in the drawings, and duplicated explanations are omitted. In addition, multiple drawings include schematic diagrams, and the dimensional ratios of length, width, height, etc. of each member between different drawings do not necessarily match. In addition, among the components described below, components that are not described in the independent claims showing the highest concept are optional components and are not essential components.

[0024] Fig. 1 is a side view of a noise evaluation device 1 for a rubber piece 5 according to an embodiment of the present disclosure. As shown in Fig. 1, the noise evaluation device 1 for a rubber piece 5 (hereinafter simply referred to as a noise evaluation device) includes a horizontally moving stage 6, a horizontally displacing mechanism 10 for translationally displacing (translating) the horizontally moving stage 6 in a first direction (in this embodiment, the horizontal direction indicated by arrow A), a rubber holding member 20 rotatably fixed to the horizontally moving stage 6 and holding the rubber piece 5, a rotation servo motor 25 for rotating the rubber holding member 20 relative to the horizontally moving stage 6, a contact member 30 that contacts the rubber piece 5, an accelerometer 35 fixed to the rubber piece 5, and A data analysis device 50 is provided.

[0025] The horizontal displacement mechanism 10 and the rotation servo motor 25 constitute an actuator that causes the rubber piece 5 to perform a swing displacement (swing movement in the direction indicated by arrow C) including a translational displacement (translational movement in the direction indicated by arrow A) and an arcuate displacement (arc movement in the direction indicated by arrow B) relative to the simulated road surface 30a. The rubber piece 5 is made of the same material as the tire whose noise is to be evaluated. In this embodiment, the rubber piece 5 has a rectangular parallelepiped shape, and the surface that comes into contact with the simulated road surface 30a is made up of a flat surface. However, the surface of the rubber piece that comes into contact with the simulated road surface 30a may be made up of a part of a cylindrical surface that follows the contact surface of the tire.

[0026] The horizontally moving stage 6 may have any shape, and in this embodiment, it has a flat plate shape. The horizontally displacing mechanism 10 includes the horizontally moving stage 6 and a linear slider capable of displacing the hanger plate 34 relative to a fixed base (a stationary portion of a test room) 31. More specifically, the horizontally displacing mechanism 10 includes the fixed base 31, guide rails 32 provided on both the left and right ends of the fixed base 31, a slider 33 that forms a linear guide in combination with the guide rail 32, a hanger plate 34 that is integral with the slider 33 and is provided to move along the guide rail 32, and a linear motor 43. The linear motor 43 includes a yoke (not shown) fixed in parallel on the fixed base 31, a plurality of permanent magnets 37 arranged along the yoke, a core 38 formed by laminating electromagnetic steel plates that are provided to face the permanent magnets 37 via a magnetic gap, and a coil 39 wound around a winding storage portion of the core 38. The coil 39 is fixed to the core 38 by, for example, a resin mold.

[0027] The yoke and permanent magnet 37 form a stator 45 of the linear motor 43, and the core 38 and coil 39 form a mover 41 (linear motor armature) of the linear motor 43. The mover 41 is fixed to the hanger plate 34. A driving current is supplied to the coil 39 from a power source (not shown) via a power supply cable 42. Although not shown, a Cableveyor (registered trademark) that supports and guides the power supply cable 42 with a caterpillar structure or the like is provided on the side of the linear motor 43. The Cableveyor has a slide mechanism that reciprocates the power supply cable 42 in accordance with the movement of the mover 41.

[0028] The data analysis device 50 controls the direction and value of the current flowing through the coil 39 using at least one of wired and wireless communication. The hanger plate 34 receives a force in the first direction indicated by the arrow A based on the magnetic field generated by the current flowing through the coil 39 and the magnetic field generated by the permanent magnet 37, and moves in the first direction. The horizontal movement stage 6 is fixed to the hanger plate 34. As a result, the horizontal movement stage 6 moves in the first direction in conjunction with the movement of the hanger plate 34 in the first direction. The first direction is a direction approximately parallel to the horizontal plane. The speed of the hanger plate 34 is controlled with high precision based on the value of the current flowing through the coil 39. In addition, by controlling the direction of the current flowing through the coil 39, the hanger plate 34 can be moved in the first direction (from left to right on the paper surface of FIG. 1).

[0029] The rotation servo motor 25 is fixed to the horizontal movement stage 6 and moves in the first direction together with the horizontal movement stage 6. The output shaft (rotation shaft) 25a extends in a second direction that is substantially perpendicular to the first direction. The second direction is also substantially parallel to the horizontal plane, similar to the first direction. In this embodiment, the rubber holding member 20 has a substantially rectangular parallelepiped shape. When the rubber holding member 20 is located at the lowest point, the upper and lower surfaces of the rubber holding member 20 extend substantially parallel to the horizontal plane. The rubber holding member 20 is fixed to the output shaft 25a. The output shaft 25a extends in the thickness direction of the rubber holding member 20. The center axis of the output shaft 25a is located on the upper side of the rubber holding member 20 and on the vertical bisecting plane of the rubber holding member 20.

[0030] The contact member 30 is fixed on a base 40. A pseudo road surface 30a is formed on the upper surface of the contact member 30. The pseudo road surface 30a may be formed of any road surface that can simulate a road surface, and may be formed of the same road surface as any one of the many asphalt road surfaces actually used. The pseudo road surface 30a may be formed of an aluminum smooth road or the like. The base 40 is capable of adjusting the height position of the pseudo road surface 30a by a known height adjustment mechanism, for example, an adjuster or the like. The rubber piece 5 is fixed to the lower surface of the rubber holding member 20 by using a fixing means, for example, a double-sided tape or the like.

[0031] When a current is applied to the coil 39, the rotation servo motor 25 is rotated at the same time. Then, the horizontally moving stage 6 translates in the first direction, and at the same time, the rubber holding member 20 makes an arcuate displacement (rotational movement) around the center of the output shaft 25a of the rotation servo motor 25 relative to the horizontally moving stage 6. As a result, the rubber piece 5 translates in the first direction and at the same time makes an arcuate displacement. When the rubber holding member 20 having a rectangular front shape extends in the height direction, the rubber piece 5 reaches its lowest point. At the timing when the rubber piece 5 reaches its lowest point, the entire or substantially entire lower surface of the rubber piece 5 is in contact with the simulated road surface 30a, and the contact pressure of the rubber piece 5 against the simulated road surface 30a becomes maximum.

[0032] When the rubber piece 5 reaches its lowest point, the vertical load applied to the rubber piece 5 as it comes into contact with the simulated road surface 30a can be adjusted with high precision by adjusting the height position of the base 40. The translational movement of the horizontally moving stage 6 in the first direction imitates the linear movement of a vehicle, and the rotational movement of the rubber piece 5 relative to the horizontally moving stage 6 imitates the rotational motion of a tire rotatably fixed to the vehicle.

[0033] The accelerometer 35 is fixed to the end surface of the rubber piece 5 on the opposite side to the direction of rotation using a fixing means such as double-sided tape. The accelerometer 35 is formed, for example, of a MEMS acceleration sensor fabricated using MEMS (Micro Electro Mechanical Systems) technology. The accelerometer 35 may be formed of a capacitance-type acceleration sensor that detects slight position changes in a minute moving part supported by a beam structure as changes in capacitance and amplifies and measures the change by an electric circuit. Alternatively, the accelerometer 35 may be formed of a piezo-resistance-type acceleration sensor that detects position changes in a diaphragm formed by a silicon semiconductor manufacturing technology using a piezo-resistance element and amplifies and measures the detected physical quantity by an electric circuit.

[0034] The accelerometer 35 is connected to a wire (not shown) that transmits detected information and a wireless transmitter (not shown) that is electrically connected to the wire. Information based on the detected information detected by the accelerometer 35 and transmitted by the wireless transmitter is received by a wireless receiver (not shown) that is electrically connected to the data analysis device 50, so that the detected information detected by the accelerometer 35 can be analyzed by the data analysis device 50. The wireless transmitter and wireless receiver constitute a collection unit that collects output data output from the accelerometer 35. Note that a connection terminal for inputting an external signal may be provided in the friction tester of the noise evaluation device. The accelerometer 35 may be preferentially connected to an external terminal of the friction tester, and the friction tester may be connected to the data analysis device 50.

[0035] The data analysis device 50 is composed of an information terminal, for example, a personal computer or a workstation. The data analysis device 50 includes an input unit 51, a display unit 52, a transmission / reception unit 53, and a control device 64. The input unit 51 is used to input data and is composed of, for example, a keyboard and a mouse. The display unit 52 is composed of a liquid crystal panel and displays an image. The display unit 52 may be composed of an organic EL panel. The input unit 51 and the display unit 52 may be composed of a touch panel in which a touch sensor and a display are integrated. The transmission / reception unit 53 transmits and receives information via a wireless transceiver incorporated in a network. The transmission / reception unit 53 is composed of an interface for transmitting and receiving data to and from the wireless transceiver (network). The data analysis device 50 may include an output unit 54 composed of a printer or the like, in which case data in the middle of analysis or final analyzed data can be output as appropriate.

[0036] The control device 64 is preferably configured by a computer, for example, a microcomputer, and includes a control unit 65 and a storage unit 67. The control unit 65, i.e., the processor, includes, for example, a CPU (Central Processing Unit). The storage unit 67 is configured by a hard disk drive (HDD), a solid state drive (SSD), or the like, and may include a non-volatile memory such as a ROM (Read Only Memory) or a volatile memory such as a RAM (Random Access Memory). The storage unit 67 may be configured by only one storage medium, or may be configured by a plurality of different storage media. The CPU reads out and executes programs and the like previously stored in the storage unit 67. The non-volatile memory previously stores a control program, a predetermined threshold value, and the like. The volatile memory temporarily stores the read program and processing data.

[0037] The control unit 65 includes a current control unit 65a, a motor control unit 65b, a period determination unit 65c, an accelerometer control unit 65d, a Fast Fourier Transform (FFT) unit 65e as an example of a frequency analysis unit, and a noise evaluation unit 65f. The current control unit 65a uses at least one of wired and wireless communication to pass a current through the coil 39 and controls the movement in the first direction of the horizontal movement stage 6. The motor control unit 65b uses at least one of wired and wireless communication to control the drive of the rotation servo motor 25. The period determination unit 65c determines the period for driving the accelerometer 35 based on, for example, the start time of current supply to the coil 39 or the start time of driving the rotation servo motor 25.

[0038] In this embodiment, the input unit 51 can input the moving speed of the horizontal movement stage 6 and the rotation speed of the rotation servo motor 25. Therefore, the period specifying unit 65c can specify the timing at which the rubber piece 5 reaches the lowest point and the timing at which the rear of the rubber piece 5 leaves the simulated road surface 30a. The period specifying unit 65c specifies the data collection period from the first timing at which the rubber piece 5 reaches the lowest point to the second timing at which a predetermined time has elapsed since the rear of the rubber piece 5 left the simulated road surface 30a.

[0039] In addition, rotation angle information can be obtained in real time from the rotation servo motor 25, and the data collection period can also be determined from the rotation angle. Therefore, for example, the timing when the rubber piece (sample) 5 comes directly below can be determined from the angle information, and noise can be recorded for a predetermined period of the period from stepping in to taking off based on the angle information.

[0040] The accelerometer control unit 65d controls the driving of the accelerometer 35 during the accelerometer driving period. Vibration occurs the moment the rear of the rubber piece 5 leaves the simulated road surface 30a (the moment it is kicked out). Therefore, the vibration does not subside until a certain time has passed since the rubber piece 5 is no longer in contact with the simulated road surface 30a. For this reason, it is preferable for the accelerometer control unit 65d to drive the accelerometer 35 from the first timing when the rubber piece 5 reaches the lowest point to the second timing when the output shaft 25a has rotated 15° or more, and it is more preferable for the accelerometer control unit 65d to drive the accelerometer 35 from the timing when the rubber piece 5 reaches the lowest point to the second timing when the output shaft 25a has rotated 20° or more.

[0041] Instead of driving the accelerometer 35 during the above data collection period, the accelerometer 35 may be driven at all times, and the sliding noise may be evaluated using data during the data collection period from the first timing to the second timing among the vibration data acquired from the accelerometer 35. Even in this case, the sliding noise can be evaluated with high accuracy, similar to the case where the accelerometer 35 is driven during the above data collection period.

[0042] Since the three-dimensional positions of the rubber holding member 20, the rubber piece 5, and the simulated road surface 30a can be identified at each time, the vertical load applied to the rubber piece 5 at each time can be inferred. However, it is preferable that the noise evaluation device 1 is equipped with a load cell for identifying the vertical load applied to the rubber piece 5, and is preferably capable of actually measuring the vertical load applied to the rubber piece 5. A spring-type, piezoelectric element-type, magnetostrictive-type, electrostatic capacitance-type, gyro-type, strain gauge-type, or other load cell can be employed.

[0043] In the strain gauge type, a metal foil attached to a strain gauge on an elastic body called a flexure body expands and contracts due to minute deformation, causing a change in cross-sectional area, which changes the resistance value. Since this change is proportional to the load, the load applied to the flexure body can be calculated from the change in resistance value. The strain gauge is attached to the outer surface or inside of the rubber piece 5 at a position where the vertical load applied to the rubber piece 5 can be identified, and outputs a signal to the data analysis device 50 using at least one of wires and wirelessly.

[0044] If a vertical load equivalent to the vertical load applied to an actual tire is applied to the rubber piece 5, the sliding noise can be evaluated with even higher accuracy. If the noise evaluation device 1 is equipped with a load cell, the noise evaluation test can be performed in a state where a vertical load equivalent to the vertical load applied to an actual tire is confirmed to be applied to the rubber piece 5. Furthermore, the measured value of the load cell can be used to identify the timing when the rubber piece 5 leaves the simulated road surface 30a, i.e., the timing when the vertical load becomes zero.

[0045] The fast Fourier transform unit 65e performs a fast Fourier transform as an example of frequency analysis on the vibration data from the accelerometer 35. The noise evaluation unit 65f judges whether the noise is within an allowable level based on the data of 500 Hz or more and 3000 Hz or less of the vibration data that has been subjected to the fast Fourier transform. The reason for using the data of 500 Hz or more and 3000 Hz or less of the vibration data that has been subjected to the fast Fourier transform will be explained in detail later. The data from the accelerometer 35 received by the wireless receiver may be subjected to a known processing such as amplification to make the data easier to understand, and noise analysis may be performed based on the processed data.

[0046] Fig. 2 is a diagram for explaining skid noise in tire noise. As shown in Fig. 2, in the tire 2, first, the front of the block 28 comes into contact with the road surface 21 (timing A), and then the entire block 28 comes into contact with the road surface 21 (timing B). Then, after that, the block 28 translates while remaining in contact with the road surface (timing C), the front tip of the block 28 comes out of contact with the road surface and is released from the road surface 21 (timing D), and the rear tip of the block 28 comes out of contact with the road surface 21 and is released from the road surface 21 (timing E).

[0047] In this background, it is known that, after the front end of the block 28 touches the ground, the block 28 rubs against the ground surface during the period from timing A to D enclosed by the dotted line, causing a slip phenomenon called the stick-slip phenomenon. On the other hand, it is known that, during the period from timing D to E enclosed by the dashed line, a slip phenomenon called the stick-snap phenomenon occurs. When the front end of the block 28 starts to separate from the ground surface at the timing when the block 28 is released from the ground, the radial force of that portion disappears, so that the rear of the block 28 is pulled from the front and slides to gradually separate.

[0048] It is known that tire noise increases during acceleration when a driving force is applied. It is also believed that the contribution of the sliding noise of tire blocks to the noise that increases with acceleration is large. Therefore, evaluation of the sliding noise is necessary to improve the reduction of noise that increases with acceleration. In this embodiment, a method for evaluating the sliding noise in the stick-snap phenomenon will be described. However, in the evaluation method described below, the sliding noise in the stick-slip phenomenon can be easily evaluated simply by changing the period for evaluating the noise from the period between timings D and E to the period between timings A and D.

[0049] The front and rear ends of the block 28 in the circumferential direction have large movement and large slippage, whereas the central portion of the block 28 in the circumferential direction has small movement and small slippage. In the sliding noise evaluation method of the present disclosure, the rubber piece 5 corresponds to the block 28 of the tire 2. Also, fixing the accelerometer 35 to the end face of the rubber piece 5 on the side opposite to the rotation direction corresponds to fixing the accelerometer 35 to the end face of the block 28 on the side opposite to the rotation direction. By fixing the accelerometer 35 to the end face of the rubber piece 5 on the side opposite to the rotation direction, the sliding noise in the stick-snap phenomenon can be detected with high accuracy.

[0050] When evaluating the sliding noise due to the stick-snap phenomenon, it is preferable to evaluate the sliding noise using only data from a front accelerometer located on the end face of the rubber piece 5 in the direction of rotation (front end face), or using both data from the front accelerometer and data from a rear accelerometer located on the end face of the rubber piece opposite the direction of rotation (rear end face).

[0051] Fig. 3 is a graph obtained by the noise evaluation device 1, which shows the relationship between vibration data dB obtained by applying fast Fourier transform to data based on signals from the accelerometer 35 when a slip ratio, i.e., the magnitude of slip, is set, and the vibration frequency, comparing a case where the slip ratio is 0% with a case where the slip ratio is 4%. Fig. 4 is a graph obtained by the noise evaluation device 1, which shows the relationship between vibration data dB obtained by applying fast Fourier transform to data based on signals from the accelerometer 35, and the vibration frequency, comparing a case where the slip ratio is 0% with a case where the slip ratio is 9%. Here, the slip ratio is a value calculated by the following calculation formula (1). (Rotational speed of rubber holding member 20-Translational speed of horizontally moving stage 6) / Translational speed of horizontally moving stage 6 (1)

[0052] As shown in Figures 3 and 4, when the slip ratio is either 4% or 9%, when the frequency is between 500Hz and 3000Hz and below, the vibration data is significantly larger than when the slip ratio is 0%, and a significant difference in the vibration data can be confirmed. This shows that by analyzing the frequency range between 500Hz and 3000Hz, it is possible to perform a noise evaluation that focuses on noise that increases with acceleration, i.e., slipping noise, and to accurately evaluate slipping noise.

[0053] Figures 5 and 6 are graphs showing the relationship between A-weighted sound pressure level dB and frequency in tire noise evaluation tests for vehicles equipped with different tires. Note that A-weighted characteristics are frequency weighting characteristics that take into account human hearing and are used in measurements using sound level meters, and are characteristics defined in JIS C 1502-1990 "ordinary sound level meter." In addition, in Figures 5 and 6, the dotted lines represent data when driving at a constant speed, and the solid lines represent data when driving at an accelerating speed.

[0054] As shown in Figures 5 and 6, in both actual vehicle tests, when the frequency is 500 Hz or more and 3000 Hz or less, the data when accelerating is much larger than the data when driving at a constant speed, and a significant difference in the sound pressure level data can be confirmed. From this, it can be confirmed that by analyzing the frequency range of 500 Hz or more and 3000 Hz or less, it is possible to perform a noise evaluation that focuses on noise that increases with acceleration, i.e., slipping noise, and more specifically, it can be confirmed that by performing a noise evaluation using the rubber piece of the present disclosure, it is possible to perform an accurate evaluation of slipping noise, similar to the noise evaluation of the acceleration test of the actual vehicle test using the prototype tire.

[0055] Fig. 7 is a graph showing an example of the test results of the noise evaluation device 1, which graph shows the relationship between the acceleration level and the slip ratio. The acceleration level on the vertical axis of Fig. 7 is the partial overall value, which is the sum of the power of each frequency band of the power spectrum in the frequency range of 500 Hz to 3000 Hz. In the noise evaluation test shown in Fig. 7, the acceleration level increases at a slip ratio of 4% and decreases thereafter. From this, it was confirmed that the rubber piece 5 used in the test shown in Fig. 7 is less likely to enter a stick state when the sliding speed is too fast, and the acceleration at the start of the push-off decreases.

[0056] Fig. 8 is a graph showing another test result of the noise evaluation device 1, which is a graph showing the relationship between the acceleration level and the slip ratio. The acceleration level L on the vertical axis of Fig. 8 is a value calculated by the following formula (2) using the partial overall value a, which is the sum of each frequency band power of the power spectrum in the frequency range from 500 Hz to 3000 Hz. L = 20 Log (a / a0) [dB] (2) a: Vibration acceleration (unit: m / s 2 ) a0: Reference vibration acceleration (10 -6 m / s 2 )

[0057] In the noise evaluation test shown in Fig. 8, the acceleration level increases as the slip ratio increases. This confirms that the rubber piece 5 used in the test shown in Fig. 8 is prone to becoming stuck when the sliding speed is too fast, and the acceleration at the start of the push-off increases.

[0058] Whether or not the rubber piece 5 used in the noise evaluation test has excellent sliding noise characteristics may be determined by comparing data based on frequency analysis data obtained by frequency analysis of data based on the output data output by the accelerometer 35 with a threshold value. For example, data in a frequency range of 500 Hz to 3000 Hz inclusive in a graph showing the relationship between vibration data and vibration frequency shown in Fig. 3 is compared with a threshold value S, and if the vibration value at at least one frequency is less than the threshold value S, it may be determined that the material constituting the rubber piece 5 has excellent sliding noise characteristics, and in other cases, it may be determined that the material constituting the rubber piece 5 has poor sliding noise characteristics.

[0059] Alternatively, the partial overall value, which is the sum of the power of each frequency band of the power spectrum in the frequency range of 500 Hz to 3000 Hz, may be compared with a threshold value, and if the partial overall value is less than the threshold value, it may be determined that the material constituting the rubber piece 5 has excellent sliding noise characteristics, and otherwise it may be determined that the material constituting the rubber piece 5 has poor sliding noise characteristics. These determinations are made by the noise evaluation unit 65f.

[0060] As described above, the noise evaluation method for a rubber piece 5 according to the present disclosure includes the steps of fixing an accelerometer 35 to the rubber piece 5, contacting the outer surface of the rubber piece 5 with the pseudo road surface 30a while the rubber piece 5 is undergoing a swing displacement including translational displacement and circular displacement relative to the pseudo road surface 30a, and collecting output data from the accelerometer 35 during a data collection period that includes at least a portion of the contact period during which the rubber piece 5 and the pseudo road surface 30a are in contact, performing frequency analysis on data based on the output data during the data collection period, and evaluating the noise based on the frequency analysis data obtained by frequency analysis.

[0061] According to the present disclosure, a noise test is performed by contacting the rubber piece 5 with the simulated road surface 30a while simultaneously displacing it in a translational manner in the horizontal direction and displacing it on a circular arc, so that the rubber piece 5 can be displaced in the same manner as the outer circumferential surface of an actual tire, allowing the noise test to be performed accurately, and the translational displacement can cause the rubber piece 5 to slip, making it easy to accurately evaluate the slipping noise. Also, according to the present disclosure, the test is performed using only the rubber piece 5, eliminating the need to create a test tire, thereby reducing the labor and testing costs required for the test.

[0062] In addition, the data collection period may be the period from a start timing, which is the timing when the contact pressure of the rubber piece 5 against the pseudo road surface 30a becomes maximum, to an end timing, which is later than the start timing and during which the rubber piece 5 is positioned at a distance from the pseudo road surface 30a.

[0063] According to this configuration, the slipping noise caused by the stick-snap phenomenon can be accurately evaluated.

[0064] Furthermore, noise may be evaluated based on data in the range of 500 Hz to 3000 Hz among frequency analysis data obtained by frequency analysis.

[0065] According to this configuration, it is easy to accurately evaluate noise caused by slipping.

[0066] Additionally, noise may be evaluated by comparing data based on frequency analysis data with a threshold value.

[0067] According to this configuration, noise caused by slippage can be easily evaluated objectively and accurately using a simple method.

[0068] The noise evaluation device 1 also includes an accelerometer 35 fixed to the rubber piece 5, actuators (a horizontal movement servo motor 11 and a rotation servo motor 25) that cause the rubber piece 5 to perform a swing displacement including a translational displacement and a circular displacement relative to the pseudo road surface 30a, and the pseudo road surface 30a that comes into contact with the rubber piece 5 during at least a portion of the period during which the rubber piece 5 performs the swing displacement.

[0069] According to the present disclosure, a noise test can be performed by contacting a simulated road surface with the rubber piece 5 in a translational displacement and at the same time displaced on a circular arc. Therefore, the rubber piece 5 can be moved in the same manner as the movement of the outer circumferential surface of an actual tire, making it possible to perform a noise test accurately, and the translational displacement can cause the rubber piece 5 to slip, making it easy to accurately evaluate the slipping noise. Furthermore, according to the present disclosure, the test can be performed using only the rubber piece 5, and there is no need to prepare a test tire, so the labor and testing costs required for the test can be reduced.

[0070] The noise evaluation device 1 may also include a period identification unit 65c that identifies a data collection period including at least a part of the contact period during which the rubber piece 5 and the pseudo road surface 30a are in contact with each other, a fast Fourier transform unit 65e (frequency analysis unit) that performs frequency analysis of data based on output data from the accelerometer 35 during the data collection period, and a noise evaluation unit 65f that evaluates the noise based on the frequency analysis data frequency analyzed by the fast Fourier transform unit 65e.

[0071] According to this configuration, it is easy to evaluate the slippage noise with high accuracy.

[0072] The present disclosure is not limited to the above-described embodiment and its modified examples, and various improvements and modifications are possible within the scope of the claims of the present application and their equivalents.

[0073] For example, in the above embodiment, the data collection period was the period from the first timing when the rubber piece 5 reached its lowest point to the second timing when a predetermined time had elapsed since the rear of the rubber piece 5 left the simulated road surface 30a. However, the data collection period may be the period from the first timing when the rubber piece 5 is in contact with the simulated road surface 30a after the rubber piece 5 reaches its lowest point to the second timing when a predetermined time had elapsed since the rear of the rubber piece 5 left the simulated road surface 30a, and even in this case, the slippage noise caused by the stick-snap phenomenon can be accurately evaluated.

[0074] Alternatively, the data collection period from the accelerometer 35 may be included in the period from the first timing when the front of the rubber piece 5 comes into contact with the simulated road surface 30a to the second timing when the front of the rubber piece 5 leaves the simulated road surface 30a. In this way, the slip noise caused by the slippage of the stick-slip phenomenon can be accurately evaluated.

[0075] In addition, the frequency analysis was performed by applying a fast Fourier transform to the extracted acceleration data, but the frequency analysis may be performed by applying a Fourier transform instead of the fast Fourier transform.Furthermore, the frequency analysis may be performed on the output data collected from the accelerometer during the data collection period itself, or on data obtained by processing the output data collected from the accelerometer during the data collection period.

[0076] Also, the case where the slipping noise is evaluated using the partial overall value, which is the sum of the power of each frequency band of the power spectrum in the frequency range of 500 Hz to 3000 Hz, has been described. However, the slipping noise may also be evaluated using the overall value, which is the sum of the power of each frequency band of the analyzed power spectrum.

[0077] Also, the case has been described where the pseudo road surface 30a is stationary and the horizontally moving stage 6 to which the rubber holding member 20 is rotatably fixed is translated. However, the pseudo road surface 30a (base 40) may be translated and the stage to which the rubber holding member is rotatably fixed may be stationary.

[0078] Also, the horizontal displacement mechanism 10 has been described as moving the horizontal movement stage 6 in the first direction using a linear slider. However, the horizontal movement stage 6 may be moved in the first direction by a mechanism other than the linear slider. For example, as shown in FIG. 9, the horizontal displacement mechanism 110 may have a horizontal movement servomotor 111, a horizontal movement ball screw 112, and the horizontal movement stage 6. The horizontal movement ball screw 112 includes a screw shaft 115 extending horizontally and a nut 116 screwed thereto. The screw shaft 115 is coupled to an output shaft 117 of the horizontal movement servomotor 111 via a coupling 118.

[0079] The horizontal movement ball screw 112 and the horizontal movement servo motor 111 are fixed to a fixed frame (a stationary part of a test room) not shown. Furthermore, a nut 116 screwed onto the screw shaft 115 is fixed to the horizontal movement stage 6. As a result, when the output shaft 117 of the horizontal movement servo motor 111 rotates in the direction of arrow D, the horizontal movement stage 6 moves in a first direction (a direction substantially parallel to a horizontal plane) indicated by arrow A via the nut 116 screwed onto the screw shaft 115.

[0080] In this mechanism, the horizontal movement servomotor 111 is rotated and the rotation servomotor 25 is rotated at the same time. Then, the horizontal movement stage 6 is translated in the first direction, and at the same time, the rubber holding member 20 can be displaced in an arc (rotational movement) around the center of the output shaft 25a of the rotation servomotor 25 relative to the horizontal movement stage 6.

[0081] In the data analysis device 150 of the noise evaluation device 101, the control unit 165 of the control device 164 has a motor control unit 165a, a period determination unit 165b, an accelerometer control unit 165c, a fast Fourier transform unit 165d, and a noise evaluation unit 165e. The motor control unit 165a controls the driving of the horizontal movement servomotor 11 and the rotation servomotor 25 using at least one of wired and wireless communication. The period determination unit 165b determines the period for driving the accelerometer 35, for example, based on the driving start times of the horizontal movement servomotor 111 and the rotation servomotor 25.

[0082] The input unit 151 can input the rotation speeds of the horizontal movement servo motor 11 and the rotation servo motor 25. Therefore, the period determination unit 165b can determine the timing when the rubber piece 5 reaches the lowest point and the timing when the rear of the rubber piece 5 leaves the simulated road surface 30a. For example, the period determination unit 165b determines the data collection period from the first timing when the rubber piece 5 reaches the lowest point to the second timing when a predetermined time has elapsed since the rear of the rubber piece 5 leaves the simulated road surface 30a. The configurations of the display unit 152, the transmission / reception unit 153, and the output unit 154 are the same as the configurations of the display unit 52, the transmission / reception unit 53, and the output unit 54. In addition, the operations of the accelerometer control unit 165c, the fast Fourier transform unit 165d, the noise evaluation unit 165e, and the storage unit 167 are the same as the operations of the accelerometer control unit 65d, the fast Fourier transform unit 65e, the noise evaluation unit 65f, and the storage unit 67.

[0083] In the above embodiment and modified example, the rubber piece 5 is caused to perform a swing displacement that is a combination of a translational displacement and a circular displacement. However, the rubber piece may be caused to perform a displacement that includes a translational displacement, a circular displacement, and a height-direction displacement. Such a noise evaluation device can be easily realized by rotatably fixing the rubber holding member using a rotation servo motor to a height-direction moving stage that is fixed to the above-mentioned horizontal moving stage so as to be movable in the height direction using a guide rail or the like by a height-direction moving linear slider.

[0084] Alternatively, such a noise evaluation device can be easily realized by rotatably fixing the rubber retaining member using a rotation servo motor to a height-direction moving stage which is fixed so as to be movable in the height direction relative to the above-mentioned horizontal moving stage using a guide rail or the like, with a height-direction moving servo motor and a height-direction moving ball screw.

[0085] According to these modified examples, the rubber piece 5 can be displaced in the height direction in addition to translational and arcuate displacements. Therefore, it is possible to more faithfully reproduce the movement of an actual tire, which may be displaced in the height direction due to the operation of the suspension, etc., and then evaluate the skid noise. [Explanation of symbols]

[0086] 1,101 Noise evaluation device, 2 Tire, 5 Rubber piece, 6 Horizontal movement stage, 10,110 Horizontal displacement mechanism, 20 Rubber holding member, 25 Rotation servo motor, 25a Rotation servo motor output shaft, 28 Tire block, 30 Contact member, 30a Simulation road surface, 31 Fixed base, 32 Guide rail, 33 Slider, 34 Hanger plate, 35 Accelerometer, 37 Permanent magnet, 38 Core, 39 Coil, 40 Base, 41 Movable element, 42 Power supply cable, 43 Linear motor, 45 Stator, 50,150 Data analysis device, 51,151 Input unit, 52,152 Display unit, 53,153 Transmitting / receiving unit, 54,154 Output unit, 64,164 control device, 65,165 control unit, 65b,165a motor control unit, 65c,165b period determination unit, 65d,165c accelerometer control unit, 65e,165d fast Fourier transform unit, 65f.165e noise evaluation unit, 67,167 memory unit, 111 servo motor for horizontal movement, 112 ball screw for horizontal movement, 115 screw shaft, 116 nut, 117 output shaft of servo motor for horizontal movement, 118 coupling.

Claims

1. affixing an accelerometer to the piece of rubber; A step of contacting an outer surface of the rubber piece with the simulated road surface while the rubber piece is undergoing a swing displacement including a translational displacement and a circular displacement with respect to the simulated road surface, and collecting output data from the accelerometer during a data collection period including at least a part of a contact period during which the rubber piece is in contact with the simulated road surface; performing a frequency analysis on data based on the output data during the data collection period; Evaluating the noise based on the frequency analyzed frequency analysis data; A method for evaluating the noise of a rubber piece, comprising:

2. 2. The method for evaluating noise of a rubber piece according to claim 1, wherein the data collection period is a period from a start timing defined by the timing at which the contact pressure of the rubber piece with the simulated road surface becomes maximum, or a start timing defined by the timing at which the rubber piece is in contact with the simulated road surface after that timing, to an end timing at which the rubber piece is positioned at a distance from the simulated road surface and after the start timing.

3. 2. The rubber piece noise evaluation method according to claim 1, wherein the data collection period is included in a period from a first timing when a front of the rubber piece comes into contact with the simulated road surface to a second timing when the front of the rubber piece leaves the simulated road surface.

4. 4. The method for evaluating noise of a rubber piece according to claim 1, wherein the noise is evaluated based on data of 500 Hz or more and 3000 Hz or less out of the frequency analysis data obtained by the frequency analysis.

5. The method for evaluating noise of a rubber piece according to claim 1 , further comprising the step of comparing data based on the frequency analysis data with a threshold value to evaluate the noise.

6. An accelerometer fixed to the rubber piece; an actuator that causes the rubber piece to perform a swing displacement including a translational displacement and a circular displacement with respect to a simulated road surface; the simulated road surface that is in contact with the rubber piece during at least a portion of the period during which the rubber piece is undergoing the swing displacement; A rubber piece noise evaluation device comprising:

7. a period determination unit that determines a data collection period including at least a portion of a contact period during which the rubber piece is in contact with the simulated road surface; a frequency analysis unit that performs frequency analysis on data based on output data from the accelerometer during the data collection period; a noise evaluation unit that evaluates noise based on frequency analysis data obtained by the frequency analysis unit; and The rubber piece noise evaluation device according to claim 6 .

Images