江苏大学机械毕业设计外文翻译.docx

1、江苏大学机械毕业设计外文翻译江苏大学机械毕业设计电磁阀外文翻译附录：Magnetoelastic Torque Sensor Utilizing a Thermal Sprayed Sense-Element for Automotive Transmission ApplicationsBrian D. KilmartinSiemens VDO Automotive CorporationABSTRACTA Magnetoelastic based Non-Contacting, Non-Compliant Torque Sensor is being developed by Siemen

2、s VDO for automotive transmission applications. Such a sensor would benefit the automotive industry by providing the feedback needed for precise computer control of transmission gear shifting under a wide range of road conditions and would also facilitate cross-platform usage of a common transmissio

3、n unit. Siemens VDO has prototyped transmission torque sensors operating on the principle of Inverse- magnetostriction, also referred to as the Inverse-Joule Effect and the Villari Effect. Magnetostriction, first documented in the mid 1800s, is a structural property of matter that defines a material

4、s dimensional changes as a result of exposure to a magnetic field. Magnetostriction is caused when the atoms that constitute a material reorient in order to align their magnetic moments with an external magnetic field. This effect is quantified for a specific material by its saturation magnetostrict

5、ion constant, which is a value that describes a materials maximum change in length per unit length.Inverse-magnetostriction, conversely, defines changes in a materials magnetic properties in response to applied mechanical forces. Material that is highly magnetostrictive and elastic in nature is refe

6、rred to as being magnetoelastic. The premise of the Siemens VDO torque sensor design is that a magnetoelastic material can be bonded to a cylindrical shaft and magnetized in its mechanical quiescent state to create a sense- element. While under torque, principle tensile and compressive stress vector

7、s in the form of counter- spiraling, mutually orthogonal helices develop in the shaft and are conveyed to the magnetoelastic sense-element giving rise to a measurable magnetic field change. The magnetic field deviation that arises from the magnetoelastic sense-element is directly proportional to the

8、 magnitude of the imposed torque. In effect, the magnetic field is modulated by torque. A sensitive magnetometer then translates the field strength into an analog voltage signal, thereby completing the torque-to-voltage transducer function.Critical to the success of the Siemens VDO torque sensor des

9、ign is an intimate attachment of the sense- element to the torque-bearing member. Inconsistencies in the boundary between the sense-element and the torque-bearing member will result in aberrant coupling of stresses into the sense-element manifesting in performance degradation. Boundary inconsistenci

10、es can include such imperfections as voids, contaminates, lateral shearing, and localized zones of stress pre-load. Such inhomogeneities may be inherent to an attachment method itself or may subsequently be caused by systemically rendered malformations. Thermal spray, the process where metal particl

11、es are deposited onto a substrate to form a coating, was used to address the issue of securely affixing magnetic material to a torque-bearing member. In addition to achieving the prerequisite of an intimate and secure bond, the thermal spray process can be regulated such that the deposited magnetic

12、material is pre-loaded with the internal stresses needed to invoke the inverse- magnetostriction effect. Summarizing, the passive nature of the magnetic sense- element provides an intrinsically simple kernel for the Siemens VDO torque sensor that makes for a highly reliable and stable design. The th

13、ermal spray process adds robustness to the mechanical aspect by permitting torque excursions to an unprecedented 2000% of full scale (per prototype validation testing of certain constructs) without the need for ancillary torque limiting protection devices. Furthermore, accuracy, repeatability, stabi

14、lity, low hysteresis, rotational position indifference, low cost and amenability to the high-volume manufacturing needs of the automotive marketplace are all attributes of this torque sensing technique. When coupled with a magnetometer that is grounded in well- established fluxgate technology, the r

15、esultant sensor is inherently dependable and can potentially establish a new standard for torque measuring sensors. INTRODUCTIONAs is well known, automotive transmissions are designed to alter the power transfer ratio between the engine and the drive wheels effectively optimizing engine loading. The

16、 engine thereby runs in a narrow and efficient operating band even though the vehicle travels over a wide range of speeds. For automatic transmissions, shift valves select the gear ratio based generally on the throttle position, engine vacuum and the output shaft governor valve state. With the adven

17、t of electronic sensors and computerized engine controllers, transmission shift functions have been migrating towards closed-loop operation under software processing control. Along with this progression came the realization that the transmission output torque would provide a valuable feedback parame

18、ter for shift and traction control algorithms. The measurement of output torque, however, proved elusive due to the extremely harsh operating conditions. One particular SUV application under consideration required 1% accuracy in measurements of roughly 2700 Nm with possible torque excursion of 4700

19、Nm; all while exposed to temperature extremes -45 to +160 o C. One method for measuring torque is to examine the physical stresses that develop in a shaft when it is subjected to an end-to-end twisting force. The principle stresses are compressive and tensile in nature and develop along the two coun

20、ter-spiraling, mutually orthogonal 45 o helices. They are defined by the equation : t = Tr / JWhere T is the torque applied to the shaft, r is the shaft radius and J is the polar moment of inertia.Setting p r4/ 2 = J for a solid cylindrical shaft and r = d/2 yields: t = 16T / p dOnce again, T is the

21、 torque applied to the shaft and d is the shaft diameter.Furthermore, the degree of twist experienced by the shaft for a given torque is given by2: q = 32(LT) / (p d4G)Where L is the length of the shaft, T is the applied toque, d is the diameter of the shaft and G is the modulus of rigidity of the s

22、haft. The modulus of rigidity defines the level of elasticity of the shaft material, thus, a lower G value would manifest in a shaft with a higher degree of twist for any given applied torque. Torque induced stresses that occur in the shaft material are transferred into an affixed magnetic coating a

23、nd give rise to measurable changes in its surrounding magnetic field that are directly proportional to the magnitude of the applied torque; with the polarity of the magnetic field, i.e., north or south, governed by the direction of the applied torque. In essence, this is the premise of torque sensin

24、g by means of inverse magnetostriction. TORQUE SENSOR EMBODIMENTTo effectively invoke the inverse-magnetostriction effect, the magnetic material must be correctly pre-loaded with stress anisotropy in its quiescent state. In the case of a cylindrically shaped magnetic element, the anisotropic forces

25、must be circumferential (i.e., tangential) in nature and can be either compressive or tensile depending on the polarity or sign of the materials saturation magnetostriction constant. Achieving a homogenous pre-load throughout the magnetic material is crucial if the sensor is to accurately interpret

26、torque regardless of its rotational position within a stationary magnetometer. POSITIVE MAGNETOELASTIC DEVICESEarlier efforts to create such a torque sensing element relied on a sense element made of material with a positive saturation magnetostriction constant. This embodiment was realized with a r

27、ing-shaped magnetoelastic element made from 18% nickel-iron alloy that intrinsically requires tensile circumferential pre- loading 3 . Such a pre-load was achieved by pressing the ring onto a tapered area of the base shaft effectively stretching it. The effect of tensile stress on the magnetic hyste

28、resis behavior is shown in Figure 1 where the remnant inductance, B r , nearly triples. The “easy-axes” of the magnetic domains align circumferentially due to the anisotropy defined by the principal tensile stress vector. When magnetically biased, the system in effect operates as a circumferentially

29、 shorted magnet with B approaching B r and H approaching zero. NEGATIVE MAGNETOELASTIC DEVICESTo advance the state of the art, Siemens VDO Automotive has opted for a magnetoelastic element witha negative saturation magnetostriction constant. In this case, the alloy is very high in nickel content exh

30、ibiting a saturation magnetostriction, l s , in the range of -3e-5 dl/l and requires the stress pre-load to be tangentially compressive in nature. To achieve this embodiment, the magnetoelastic material that constitutes the sense element is “deposited” onto the base shaft using a high- velocity-oxyg

31、en-fuel (HVOF) thermal spray process. The coating thickness is only 0.5mm with an axial length of 25mm. The sense element material is endowed with compressive stress by means of precise control of the thermal spray process parameters. This proprietary procedure transforms a deposition process that n

32、ormally confers isotropic material properties into one that renders the requisite stress anisotropy. Prototype FabricationMagnetoelastic ElementThe specification for the shaft requires the measurement of torque levels of 2700 Nm with no deleterious effects following exposures of up to 4700 Nm. Opera

33、ting temperature is -45 o C to 160 o C. By converting from the earlier torque sensor “pressed-on ring” concept to one based on a magnetoelastic material with a negative saturation magnetostriction constant, l s , the design is advanced in several respects. Primarily, its resiliency against stress/corrosion cracki