Differential screw hardness measuring device

Abstract

The invention discloses a differential screw hardness measuring device, and overcomes the problem that the conventional hardness measuring device cannot be compact in structure, long in service life, accurate in measurement and low in cost at the same time. The differential screw hardness measuring device is characterized in that: the lead of a first thread at the lower end of a double-thread screw is P1, the lead of a second thread at the upper end is P2, and the P1 minus the P2 equals to delta P which is a relatively small numerical value; a first nut is arranged outside the first thread; the first nut is fixedly connected with the upper end of an inner sleeve; the lower end of the inner sleeve is fixedly connected with a force sensor; a second nut is arranged outside the second thread; the second nut is fixedly connected with the upper end of an outer sleeve; a tiny displacement distance is formed at the meshing position of a first driven gear and a second driven gear with a driving gear. The differential screw hardness measuring device has the following benefits: relatively small displacement can be generated through adopting a screw with a relatively large lead, so that the contradiction among accurate measurement of indentation depth residual increment, strength of screws and nuts and service life is solved; besides, a displacement sensor is avoided, so that the whole system is simpler in structure, low in cost and high in reliability.

Description

technical field [0001] The invention belongs to the technical field of hardness detection equipment, in particular to a differential screw hardness measurement device. Background technique [0002] At present, the hardness measuring devices that use the static test method to detect the hardness of metal materials and products often use three detection methods: Brinell, Rockwell and Vickers. In principle, a standard indenter with high hardness is used Press into the surface of the sample with the specified test force, measure the geometric dimensions of the indentation after the test force is removed, and calculate the hardness value according to the measurement results. The Brinell hardness test method and the Rockwell hardness test method are both for pressure measurement. First add the initial test force F 0 , plus the main test force F 1 , at the total test force F 0 +F 1 Under the action, the indenter is pressed into the surface of the sample, and the main test force...

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Problems solved by technology

[0003] Existing hardness measuring devices often adopt a lever loading method in providing test force. The problem with this method is that it is bulky and it is not convenient to be used as an independent working unit on an automatic measuring device.

[0004] Existing hardness measuring devices also adopt the hydraulic transmission loading method in providing test force. The problem with this method is that it is difficult to control the test force. The precise control of the test force requires a sophisticated and complex hydraulic servo control system. Manufacture and maintenance are more difficult

[0005] In terms of providing test force, existing hardness measuring devices also adopt servo motor drive, screw transmission and pressure sensor feedback loading methods. The problem with this method is that the transmission accuracy is greatly affected by the machining accuracy of the screw and nut.

[0006] In order to accurately measure the residual increment of indentation depth and calculate the hardness value based on the residual increment of indentation depth, existing hardness measuring devices need to be equipped with displacement measuring devices, such as dial indicators, screw micrometers, encoders or displacement sensors , among them, mechanical measurement methods such as dial indicators and spiral micrometers cannot automatically collect data and cannot be applied to automatic measurement devices

The use of an encoder to measure the displacement of the indenter needs to be matched with a precise screw transmission mechanism, and the use of a precision screw transmission mechanism to achieve precise displacement measurement requires accurate measurement of the rotation angle of the screw or nut. Under the same measurement accuracy of the rotation angle, the lead of the screw The smaller it is, the higher the accuracy of displacement measurement will be, but reducing the lead of the screw will inevitably reduce the thread strength, reduce the bearing capacity and service life of the thread, because the screw transmission mechanism in the hardness measurement device must provide precise displacement and at the same time The test force is transmitted, and when the small thread transmits the large test force, it is easy to wear, and the screw transmission accuracy will be reduced after wear, so the method of reducing the screw lead cannot provide long-term stable measurement accuracy

There are two problems in using displacement sensor to measure the residual increment of indentation depth. First, due to the limitation of the mechanical structure of the measuring device, the measurement axis of the sensor cannot coincide with the axis of the indenter, and there is a certain offset, which will introduce additional measurement errors. ; Second, the price of the displacement sensor is expensive, which also limits the promotion of this scheme

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