JP6448648B2 - A method to measure the fatigue properties of raw materials for endless flexible metal bands of drive belts - Google Patents

Description

  The present disclosure relates to a method for measuring the fatigue properties of raw materials for an endless flexible metal band. Such metal bands are known from their application in drive belts for power transmission between two adjustable pulleys of known continuously variable transmissions, which are mainly applied in motor vehicles. A drive belt of this type is known, for example, from EP-A-1815160. The drive belt comprises a plurality of plate-like transverse elements, the transverse elements being slidably incorporated in the drive belt in at least one stacked endless pulling means of the drive belt. Laminated endless pulling means consists of a set of endless and flexible metal bands superimposed on each other.

  During operation in the transmission, the drive belt is rotated around the transmission pulley by the transmission pulley. As a result, the metal band of the drive belt is alternately bent and stretched, and is typically strained to varying degrees in multiple stress cycles during the life of the drive belt in the transmission. . Thus, resistance to fatigue failure of the metal band, that is, fatigue strength is an important characteristic of the metal band. Typically, metal bands are thereby produced from maraging steel raw materials. The maraging steel raw material preferably has high fatigue strength properties, including precipitation hardening and surface nitriding process steps, and is relatively suitable for processing the raw material into an endless, flexible metal band that is the final product. Combine with possibilities.

  As part of the drive belt manufacturing process, i.e. as part of the drive belt quality assurance, at least the bending fatigue strength of the raw material is regularly measured and compared with predetermined requirements for it. In addition, such bending fatigue tests are used in the development of drive belts, in particular in the selection and optimization of process steps used in the manufacture of drive belt metal band components (new) raw materials and / or drive belts. Play an important role.

  Several test methods are available in the prior art for measuring, ie quantifying, the bending fatigue strength of metals. Typically, in each such test method, a strip-like or rectangular specimen is cycled until failure due to fatigue failure is determined depending on the mean value and amplitude of the applied bending stress. Subject to changing bending stresses and multiple stress cycles. However, known test methods differ in the manner in which bending stress is introduced into the specimen. In one such known test method, a strip-shaped specimen is bent along its length and the first one distal end of such bent specimen is fixed. In contrast, the other distal end of the test strip is vibrated so as to approach or leave the first one distal end by a linear actuator. This latter test method is preferred. This is because the maximum bending stress (and hence the ultimate fatigue failure of the specimen) occurs at a well-defined fulcrum of bending applied to the specimen. Furthermore, in this latter test method, the maximum bending stress is directly related to the magnitude of the displacement imposed on the other distal end of the specimen by a linear actuator.

  A typical limitation of this latter test method and other known test methods for measuring bending fatigue strength is that the frequency of stress vibrations obtained in this method is on the order of about 50 Hz, which is at least typical. In particular, the number of bending stress cycles required before breakage in the industry is quite limited. In particular, if the average value and amplitude of the bending stress applied to the specimen is set to correspond to the average value and amplitude of the bending stress that occurs in the currently considered drive belt application of the raw material, Even a single measurement of bending fatigue strength can easily take several weeks to complete. Further, during such measurements, considerable power is consumed by the linear actuator, and a total power consumption of 250 kWh to complete the measurement is not uncommon.

  The present disclosure aims at improving the latter known test method, in particular from the viewpoint of at least the reduction of the total power consumption, but preferably also from the viewpoint of increasing the frequency of stress oscillations that can be achieved therewith. Objective. Furthermore, the specimen is preferably exposed to the same (test) stress, so that the measurement result can continue to be correlated with another measurement result.

  According to the present disclosure, a novel method for measuring the fatigue properties of raw materials for a flexible metal band of a drive belt ring is provided for endless, i.e., circular or ring shaped, raw material specimens and such test rings. Providing a mounted spring, the test system for the test ring and the spring includes a cycle time that approximately matches the resonant frequency of the system, for example to make fatigue strength measurements until fatigue failure of the test ring occurs. Compressed and decompressed or excited periodically with frequency. By exciting such a test system at its resonant frequency, the power required for the bending fatigue strength operation, i.e. the power required for bending stress oscillations in the test ring, in particular the latter known test. It is preferably reduced over the method.

  The spring of the test system preferably allows the resonance frequency to be influenced by simply adapting the spring (force) constant. Furthermore, the spring allows the mean value of bending stress to be influenced by simply prestressing the spring and specimen system prior to vibration. In addition, this new fatigue test method can use the same or similar linear actuator as before, as in the latter known test method.

  In a first detail of the novel fatigue test method, an additional mass is provided in the test system, preferably between the test ring and spring, separately from the test ring and spring of the test system. In practice, such mass can be in the form of a connector, such as a metal clamp, provided between the test ring and the spring and connecting the test ring and the spring. By applying the mass, the amplitude of the bending stress applied to the specimen can be increased. On the other hand, by adding the mass of the test system, the resonant frequency of the specimen is reduced, but this effect can be countered by applying a stiffer spring and / or increasing the rigidity of the specimen.

  In the second detail of the novel fatigue test method, the spring is ring-shaped. This configuration of the new fatigue test method preferably allows two identical specimens to be used, i.e., tested, in a single fatigue strength measurement, thereby causing one of the specimens to break. Sometimes, the other specimen is exposed to the same number (and size) of bending stresses, so a second duplicate or confirmation measurement using such another specimen is usually quick. Can be completed. Alternatively, the size of the ring spring, i.e. in terms of its thickness, width and / or diameter, in order to influence the resonance frequency of the test system to match a suitable value for the test system. Can be adapted relatively easily.

  The above basic features of the novel fatigue test method according to the present disclosure will now be described by way of example with reference to the accompanying drawings.

1 is a schematic view in a perspective view of a known drive belt and a transmission incorporating such a known belt. 1 is a schematic view of a portion of a known drive belt having two sets of multiple flexible metal bands and multiple cross members. Fig. 2 symbolically shows a known method for producing a flexible metal band of a drive belt. 1 schematically shows a known method and configuration for measuring the bending fatigue strength of a raw material for a flexible metal band of a drive belt. 1 schematically illustrates a novel method and configuration for measuring the bending fatigue strength of a raw material for a flexible metal band of a drive belt in a first embodiment. 3 schematically shows a novel method and configuration for measuring the bending fatigue strength of a raw material for a flexible metal band of a drive belt in a second embodiment. It is two photographs of the structure for measuring the bending fatigue strength of FIG.

  FIG. 1 shows a central portion of a known continuously variable transmission that is generally applied in a power transmission path of an automobile between an engine and engine driving wheels. The transmission has two pulleys 1 and 2. Each pulley 1 and 2 is provided with two pulley disks 4 and 5. Between the pulley disks 4 and 5, there is a push type drive belt 3 for transmitting the rotational movement M and the accompanying torque from one pulley 1 and 2 to the other pulley 2 and 1. The pulley discs 4 and 5 are generally formed in a conical shape, and at least one of the pulley discs 4 is movable in the axial direction along the respective pulley shafts 6 and 7 on which both the discs 4 and 5 are arranged. Built in. The transmission usually has operating means. The actuating means applies to the at least one movable disc 4 an axially directed clamping force directed towards the respective other pulley disc 5 so that the push belt 3 is moved to the disc 4. , 5.

  The push belt 3 includes endless pulling means 31 and a plurality of relatively thin transverse elements 32. The transverse element 32 is provided in the pulling means 31 so as to be movable along the longitudinal direction of the pulling means 31, and most of the transverse element 32 is oriented laterally with respect to the longitudinal direction. The element 32 receives the tightening force, so that when the drive pulley 1 rotates, the element 32 is driven from the drive pulley 1 in the direction of the movement M by friction between the disks 4 and 5 and the push belt 3. It is propelled to the pulley 2 and back again, so that it is guided and supported by the pulling means 31. The geometric transmission ratio of the transmission is determined by the ratio between the effective contact radius R2 of the push belt 3 in the non-drive pulley 2 and the effective contact radius R1 of the push belt 3 in the drive pulley 1, and this ratio is a plurality of ratios. It may be continuously changed in the range of the value of.

  FIG. 2 shows a cross-sectional view of a known push belt, which is oriented in the longitudinal direction of the belt 3. In FIG. 2, the transverse element component 32 of the push belt 3 is shown in a front view. The transverse element 32 is incorporated in the push belt 3 and is attached to the endless tension means 31 of the push belt 3. The endless pulling means 31 consists of two stacked members, at least in this example. Each member is formed by a plurality of endless flexible metal bands 30. The metal band 30 is relatively thin and flat, with one overlaid around the other in the radial direction. Each member is accommodated in a respective opening 33 of the transverse element 32. Further, a protrusion 39 is provided on the front main surface of the transverse element 32. The protrusion 39 is accommodated in a hole (not visible) provided in the rear main surface of the adjacent transverse element 32. Protrusions 39 and holes are provided for connecting and aligning adjacent transverse elements 32 of push belt 3 to each other during operation in the transmission. The lower part of the transverse element 32 below the so-called inclined edge 36 is wedge-shaped so that when it is clamped between the disks 4 and 5 of the pulleys 1 and 2, adjacent elements 32 are centered on each other in the axial direction. Makes it possible to incline.

  FIG. 3 shows the relevant parts of a known manufacturing method for the flexible metal band component 30 of the drive belt. This known manufacturing method is generally applied in the art for the manufacture of metal drive belts 3 for automotive applications. The separate process steps of the known manufacturing method are indicated by Roman numerals.

  In the first process step I, a thin sheet or plate 11 of maraging steel base material having a thickness of about 0.4 mm is bent into a cylindrical shape and the abutted plate end 12 is in the second process step II. They are welded together to form a hollow cylinder or tube 13. In the third step III of the process, the tube 13 is annealed. Thereafter, in a fourth process step IV, the tube 13 is cut into a plurality of annular or endless rings 14, which are then stretched, usually in a fifth process step V, while being stretched. Rolled to reduce its thickness to about 0.2 mm. After rolling, the ring 14 is referred to herein as a metal band 30.

  The metal band 30 may be subjected to another annealing process step VI to remove the effect of work hardening of the previous rolling process step by recovery and recrystallization of the ring material at a temperature significantly higher than 600 ° C., eg about 800 ° C. Receive. Thereafter, in a seventh process step VII, the metal band 30 is attached to the periphery of the two rotating rollers and the metal band 30 is stretched to a predetermined circumferential length by separating the rollers. It is calibrated. In this seventh process step VII of metal band calibration, internal stress is also imposed on the metal band 30.

  Thereafter, the metal band 30 is heat treated in an eighth process step VIII of combined aging or bulk precipitation hardening and nitriding or surface hardening. In particular, such a combined heat treatment requires holding the metal band 30 in an oven chamber containing a controlled gas atmosphere containing ammonia, nitrogen and hydrogen gas. In the oven chamber, that is, the process atmosphere, ammonia molecules decompose into hydrogen gas and nitrogen atoms at the surface of the metal band 30, and the nitrogen atoms can enter the metal lattice of the metal band 30. These intervening nitrogen atoms are known to significantly enhance resistance to wear and fatigue failure. Typically, the combined aging and nitriding eighth process step VIII is performed until the nitride layer or nitrogen diffusion zone formed on the outer surface of the metal band 30 is 25-35 microns thick. A plurality of such machined endless and flexible metal bands 30 are radially stacked with a minimum of radial play or gap between each pair of adjacent metal bands 30; In other words, the endless pulling means 31 is assembled by concentrically overlapping.

  In particular, the following is noted. That is, instead, immediately after the seventh process step VII of the metal band calibration, ie before the combined aging and nitriding eighth process step VIII of the metal band 30, the tensioning means 31 is connected to a plurality of individual means. Assembly from other metal bands 30 is also known in the art. Furthermore, it is known in the art that this latter combined heat treatment (process step VIII) can alternatively be performed in two separate back-and-forth stages of aging and nitriding.

  As part of the overall manufacturing process of the metal drive belt 3, the quality of the raw material of the metal band 30 is typically tested randomly. In particular, it is practiced to use a test piece in the form of a strip 50 of maraging steel plate 11 and to measure the bending fatigue strength of this test piece. FIG. 4 schematically shows a known arrangement for this purpose of measuring the bending fatigue strength of the raw material of the flexible metal band component 30 of the drive belt.

  In FIG. 4, the test strip 50 is disposed in the length direction between the linear actuator 51 and the fixed surface 52. For the actual test of the bending fatigue strength of the test strip 50, as indicated by the arrow O in FIG. 4 until a predetermined number of vibrations of the linear actuator 51 and the test strip 50 occur or until the test strip 50 breaks. The linear actuator 51 is vibrated in the length direction of the test strip 50. In this known test configuration, the linear actuator 51 uses a significant amount of power when bending and relaxing the test sample, i.e., to generate the required vibration of bending stress in the test sample.

  In order to improve such a known bending fatigue strength test method, in particular from the viewpoint of power consumption of the test method, a new test method schematically shown in FIG. 5 was considered.

  In the new test method of FIG. 5, the test piece is provided in the form of a ring 53 and a spring 54 is attached to such a test ring 53. The linear actuator 51 is then connected to the test ring 53 or spring 54 (as shown in FIG. 5) to vibrate the entire test system 53, 54 of such test ring 53 and spring 54 at its resonant frequency. Is done. By exciting the test systems 53 and 54 at the resonant frequency, the power required for bending fatigue strength actuation, i.e. vibration of bending stress in the test ring 53, is actually compared to the known test method of FIG. Can be greatly reduced. By providing the spring 54 with specific stiffness, the resonant frequency of the new test system 53, 54 can be affected relatively easily.

  Another advantage of the new test method according to the present disclosure is that the test ring 53 applied in this test method does not have to be manufactured separately, but simply the form of the endless ring 14 which is preferably manufactured as a semi-finished product. It can be obtained from the above-described generally practiced manufacturing method for the flexible metal band component 30 of the drive belt.

  FIG. 6 illustrates an alternative embodiment of the novel test method according to the present disclosure. In this alternative embodiment, the spring 54 is provided in the form of a metal ring. This metal ring can even fit the test ring 53 (14) in its shape, size and material, and thus can also be obtained from said known manufacturing method. In addition, in the embodiment of FIG. 6, a separate mass 55 is provided in the test system 53, 54, 55 between the test ring 53 (14) and the spring 54 (14). By applying a separate mass 55, the amplitude of the bending stress applied to the specimen 53 (14) can be increased. On the other hand, the overall resonant frequency of the test system 53, 54, 55 is reduced by adding a separate mass 55, but this effect can be achieved by providing a stiffer spring 54 (14) and / or test. It can be countered by increasing the rigidity of the piece 53 (14) itself.

  FIG. 7 is a photograph of a physical embodiment of the new test method according to FIG. In this physical embodiment of the new test method, both the test ring 53 (14) and the spring 54 (14) were obtained by a commonly practiced manufacturing method for an endless flexible metal band 30. It is represented by the intermediate ring product 14. These two rings 14 are held at predetermined positions with respect to the linear actuator 51 and the fixed surface 52 by the respective magnets 56. Further, the two rings 14 are connected to each other by nut and bolt connectors 57, which also provide additional mass to the test system, i.e., test systems 53, 54, 55 (14, 14, 57).

  In fact, in FIG. 7, the test system 53, 54, 55 (14, 14, 57) is shown in operation, ie at two moments during vibration at the resonant frequency by the linear actuator 51. Yes. It can be seen from FIG. 7 that due to the resonance of the test systems 53, 54, 55 (14, 14, 57), the displacement of the separate mass 57 (55) representing the (bending) deformation of the test ring 53 It is significantly larger than the displacement. On the other hand, in the known configuration for measuring the bending fatigue strength according to FIG. 4, the (bending) deformation of the test ring 53 corresponds to the displacement of the linear actuator 51. As a result, in a new configuration for measuring bending fatigue strength, the linear actuator 51 uses significantly less power.

  The present disclosure relates to and includes all features of the appended claims in addition to all the details of the foregoing description and the accompanying drawings. Reference signs in parentheses in the claims do not limit the scope of the claims, but are provided merely as an unconstrained example of each feature. The features recited in the claims can optionally be applied separately in any product or method, but any combination of two or more of these features can also be applied.

  The invention presented by this disclosure is not limited to the embodiments and / or examples explicitly mentioned in the specification, but its amendments, modifications and practical applications, in particular the reach of those skilled in the art. The thing in is included.

Claims (6)

In a method for measuring fatigue properties of a metal test member (53),
The pre-Symbol test member (53), provided with ring-shaped mounting said to a spring (54) in the test member (53) and a spring connected to the linear actuator in one of (54) (51), said test member ( 53) and the entire spring (54) are periodically compressed and expanded at a frequency that matches at least the resonant frequency of the test system (53, 54) comprising at least the test member (53) and the spring (54). A method for measuring the fatigue characteristics of a metal test member (53), characterized by causing vibrations.   The test system (53, 54) further includes a separate mass (55), the mass (55) being mounted between the test member (53) and the spring (54) and the test. The method for measuring fatigue properties of a metal test member (53) according to claim 1, wherein the member (53) and the spring (54) are connected to each other.   The method for measuring fatigue properties of a metal test member (53) according to claim 1 or 2, wherein the spring (54) is ring-shaped and made of metal.   The method of measuring fatigue properties of a metal test member (53) according to claim 3, wherein the spring (54) fits the test member (53) in size and composition. The method for measuring fatigue characteristics of a metal test member (53) according to any one of claims 1 to 4 , wherein the fatigue characteristics are bending fatigue strength. The method of measuring is at least accidentally and / or randomly in a part of the process for producing a drive belt (3) for a continuously variable transmission or of a process for producing a drive belt (3) for a continuously variable transmission. Applied as part, the drive belt (3) includes at least one endless flexible metal band (30), and the metal test member (53) includes the endless flexible metal band (30). A method for measuring fatigue properties of a metal test member (53) according to any one of claims 1 to 5 , which is a semi-finished product.

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