DESC:SYSTEM FOR IDENTIFYING SPINNING DEFECT IN FINISHED SHOCK ABSORBER
Field of the invention:
The present invention relates to automotive shock absorbers analysis, more particularly the present invention relates to system for identifying spinning defect in finished shock absorber by experimental modal analysis technique.
Background of the invention:
Spinning is last stage in automotive shock absorber manufacturing to seal shock absorber assembly. The spinning process creates pretension load in shock absorber assembly which make sure that the shock absorber assembly is intact and takes all forces on damper in vehicle running condition.
Generally, spinning defects of the shock absorber assembly are accurately found out by strain gauging. The strain gauging is cumbersome process and requires lot of time in preparation and testing. Further, the strain gauging testing is also destructive, in the sense; the shock absorber part is cut open to find whether shock absorber is OK or NG (not good) for the pretension load developed of the spinning.
There are chances that after the shock absorber part is cut open, the shock absorber part may found OK for spinning with no spinning defect but other defect in shock absorber are responsible for non-performance of shock absorber.
Accordingly, there exists a need to provide a system for identifying spinning defect in finished shock absorber, which overcomes above-mentioned drawbacks.
Objects of the invention:
An object of the present invention is to provide a system to detect spinning defect of the automotive shock absorber due to reduced pretension loads.
Another object of the present invention is to reduce damper rejections due to spinning defect.
Summary of the invention
Accordingly, the present invention provides a system for identifying spinning defect in finished shock absorber. The system comprises a plurality of sensors, a hammer and DAQ system (data acquisition). The plurality of sensors captures the natural frequencies of the shock absorber assembly under test and sends the data to the DAQ for comparison with the data of NG shock absorber of control condition. The shock absorber finished goods tested by the system comprises conducting experimental modal analysis, confirming the spinning preload and comparing the fundamental natural frequencies for OK and NG (not good) assembly against each other.
Brief description of the drawings:
The objects and advantages of the present invention will become apparent when the disclosure is read in conjunction with the following figures, wherein
Figure 1 shows, a system for identifying spinning defect in finished shock absorber, in accordance with the present invention; and
Detailed description of the Invention:
The foregoing objects of the present invention are accomplished and the problems and shortcomings associated with the prior art, techniques and approaches are overcome by the present invention as described below in the preferred embodiments.
In one aspect, the present invention provides a system for identifying spinning defect in finished shock absorber (40). Every component of the shock absorber (40) is having its own natural frequency. Specifically, combined natural frequency of shock absorber (40) and front strut damper unit is unique for given damper configuration or design. If spinning process is not good, then pretension load on damper assembly after spinning is less, reducing the overall stiffness of the assembly. More specifically, reduced stiffness of the shock absorber (40) assembly results in lowering the natural frequency of the assembly unit.
The present invention is illustrated with reference to the accompanying drawings, wherein numbers indicated in the bracket represent the components of the invention throughout the description.
Referring to Figure 1, a system (100) for identifying spinning defect in finished shock absorber (40); (hereinafter “system (100)”) is disclosed. The finished shock absorber (40) can be a front strut or rear shock absorber. The system (100) comprises a plurality of sensors (10), a hammer (20) and DAQ system (30) (data acquisition system). The modal hammer (20) instrument provides an impulsive force in broad bandwidth upon hitting the shock absorber (40). These vibrations are measured by the sensors (10), which are vibration sensors; placed on shock absorber (40) at three locations: over rod guide area (1), over piston area (2) and over base valve area (3). Sensors (10) capturing the natural frequencies of the shock absorber (40) assembly under test, send the data to the DAQ (30). The DAQ system (30) includes multiple channels for data acquisition from sensors (10) and hammer (20). Sensors (10) and hammer (20) are connected to the DAQ (30) via communication cables. The DAQ (30) further includes a data processing module that compares the natural frequencies of the shock absorber (40) under test with that of stored frequencies of the control shock absorber (40).
Experimental modal analysis is conducted on the finished shock absorber (40) goods with OK and NG (not good) condition to find out the natural frequencies. The shock absorber (40) finished goods with OK and NG (not good) condition is tested with the system (100) for spinning preload. For the purpose of the test, the NG (not good) shock absorber is purposefully produced in control conditions. Using prior art technique the spinning preload of OK and NG shock absorber is confirmed and their fundamental natural frequencies are compared against each other.
Following tables shows normalized examples of frequencies for OK and NG shock absorber
Spinning OK part # A Fundamental Freq.
FG shock absorber 1X 2X 3X
At position 1 0.10 0.20 0.30
At position 2 0.27 0.55 0.82
At position 3 0.33 0.67 1.00

Spinning NG part # B Fundamental Freq.
FG shock absorber 1X 2X 3X
At position 1 0.00 0.01 0.01
At position 2 0.05 0.10 0.15
At position 3 0.10 0.19 0.29

Advantages of the invention
1. The method and system detects spinning defects effectively and easily with less time and with low instrumentation efforts.
2. The method and system technique helps to reduce damper rejections due to spinning defect.
3. The method and system is nondestructive technique which does not require cutting of shock absorber to check spinning defect.
4. This method can be used to find spinning defect in both front strut damper and rear dampers.
The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the precise forms disclosed, and obviously many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the present invention and its practical application, and to thereby enable others skilled in the art to best utilize the present invention and various embodiments with various modifications as are suited to the particular use contemplated. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but such omissions and substitutions are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.
,CLAIMS:Claims:
We Claim,
1. A system (100) for identifying spinning defect in finished shock absorber (40), the system (100) comprising of:
a plurality of sensors (10) for capturing the natural frequencies of the shock absorber (40) assembly;
a hammer (20) provided for creating an impulsive force in broad bandwidth upon hitting the shock absorber (40); and
a DAQ (data acquisition system) (30) including multiple channels for data acquisition from plurality of sensors (10) and hammer (20) via communication cables and comparing it with that of stored frequencies of the control shock absorber.
2. The system (100) as claimed in claim 1, wherein plurality of sensors (10) is vibration sensors.
3. The system (100) as claimed in claim 1, wherein plurality of sensors (10) positioned thereon, at three locations of the shock absorber (40) assembly: on over rod guide area (1), over piston area (2) and over base valve area (3).
4. The system (100) as claimed in claim 1, wherein the finished shock absorber (40) is any one selected from front strut damper and rear damper.

Dated this 28th day of March, 2018

Pragathi J
(Agent of Applicant),
(IN/PA- 2796)