阅读说明：本技术 用于测量螺纹的方法和测量仪器 (Method and measuring instrument for measuring a thread ) 是由 迈克尔·普许克伦克 马丁·梅夫斯 马丁·施米特-科思 于 2019-03-13 设计创作，主要内容包括：本发明涉及一种用于测量螺纹,特别是测量滚珠丝杠传动的主轴的螺纹的方法,在所述方法中,使非接触式距离传感器平行于所述螺纹的轴向方向移动；检测对应于所述距离传感器与所述螺纹的上侧之间的距离的测量信号(14)；检测具有基准值(16)的所述测量信号(14)的交点(F<Sub>S</Sub>、F<Sub>F</Sub>),所述基准值处于所述测量信号(14)的最大值与最小值之间；将彼此紧随的两个交点(F<Sub>S</Sub>、F<Sub>F</Sub>)组合成第一测量值元组,并且将彼此紧随且紧随所述第一测量值元组的两个交点(F<Sub>S</Sub>、F<Sub>F</Sub>)组合成第二测量值元组；通过所述第一测量值元组的所述交点(F<Sub>S</Sub>、F<Sub>F</Sub>)计算出第一平均值(M<Sub>n</Sub>),并且通过所述第二测量值元组的所述交点(F<Sub>S</Sub>、F<Sub>F</Sub>)计算出第二平均值(M<Sub>n+1</Sub>)；并且通过所述第一平均值(M<Sub>n</Sub>)和所述第二平均值(M<Sub>n+1</Sub>)计算出时间-角度分辨率(ZW)。通过在同一高度以非接触方式测量螺纹的螺距的牙侧,可快速精确地测量螺纹的特性,从而能够快速测量螺纹。(The invention relates to a method for measuring a thread, in particular of a spindle of a ball screw drive, in which method a contactless distance sensor is moved parallel to the axial direction of the thread; detecting a measurement signal (14) corresponding to the distance between the distance sensor and the upper side of the thread; detecting an intersection point (F) of the measurement signal (14) having a reference value (16) S 、F F ) -said reference value is between a maximum value and a minimum value of said measurement signal (14); two points of intersection (F) which will follow each other S 、F F ) Are combined into a first measurement value tuple and two intersections (F) that are to follow each other and that follow the first measurement value tuple S 、F F ) Combining into a second measurement value tuple; passing through the intersection point (F) of the first measurement value tuple S 、F F ) Calculating a first mean value (M) n ) And passing through said intersection (F) of said second measurement value tuples S 、F F ) Calculating a second average value (M) n+1 ) (ii) a And passes said first mean value (M) n ) And said second mean value (M) n+1 ) The time-angle resolution (ZW) is calculated. By measuring the flanks of the pitch of the thread at the same height in a non-contact manner, the properties of the thread can be measured quickly and accurately, enabling a quick measurement of the thread.)

1. Method for measuring a thread, in particular of a spindle of a ball screw drive, wherein

Moving a non-contact distance sensor parallel to an axial direction of the thread;

detecting a measurement signal (14) corresponding to the distance between the distance sensor and the upper side of the thread;

detecting an intersection point (F) of the measurement signal (14) having a reference value (16)_F、F_L) -said reference value is between a maximum value and a minimum value of said measurement signal (14);

two points of intersection (F) which will follow each other_S、F_F) Are combined into a first measurement value tuple and two intersections (F) that are to follow each other and that follow the first measurement value tuple_S、F_F) Combining into a second measurement value tuple;

passing through the intersection point (F) of the first measurement value tuple_S、F_F) Calculating a first mean value (M)_n-2) And passing through said intersection (F) of said second measurement value tuples_S、F_F) Calculating a second average value (M)_n-1) (ii) a And is

Passing said first mean value (M)_n) And said second mean value (M)_n+1) The time-angle resolution (ZW) is calculated.

2. A method according to claim 1, wherein the measured value (14) is determined as a function of a measurement time (12) starting from a start time or as a function of an axial displacement starting from a start position.

3. Method according to claim 1 or 2, wherein the method is performed by averaging a plurality of averages (M) from two or more immediately following measurement value tuples_n) Averaging to calculate the time-angle resolution (ZW).

4. Method according to any one of claims 1 to 3, wherein the respective measured value tuple has an intersection point (F) assigned to the rising flank of the pitch_S) And the point of intersection (F) of the falling flank assigned to the subsequent thread pitch_F)。

5. The method according to any one of claims 1 to 4, wherein the measurement of the distance sensor is triggered by a trigger fixed in the longitudinal direction of the thread.

6. The method of any one of claims 1 to 5, wherein the mean value (MP) is determined by_n) Average value (MB) of a reference measurement (20)_n) In the circumferential direction relative to a reference angular position of the thread of the reference measurement (20)

7. Method according to any one of claims 1 to 6, wherein the travel speed and/or the travel path and/or the travel time of the distance sensor is detected, wherein the first mean value (M) is passed_n) And the second mean value (M)_n+1) And/or by a plurality of successive averages (M)_n) The average of the distances therebetween to calculate a thread lead (18) of the thread.

8. The method according to any one of claims 1 to 7, wherein the thread of the main shaft of the ball screw drive is measured.

9. A measuring instrument for measuring a thread, in particular of a spindle of a ball screw drive, has

A holding device for holding the thread;

a non-contact distance sensor movable parallel to an axial direction of the thread; and

an evaluation device for evaluating the measurement signal (14) detected by the distance sensor,

wherein the evaluation device for performing the method is designed according to the method of any one of claims 1 to 8.

Technical Field

The invention relates to a method and a measuring instrument by means of which a thread can be measured.

Background

It is known to scan a ball screw driven spindle using a tactile probe to verify the characteristics of the spindle, in particular the position and pitch of the thread in the spindle.

There is a continuing need to increase the speed of thread measurement.

Disclosure of Invention

The object of the invention is to show a method that enables a quick measurement of the thread.

According to the invention, this object is achieved by a method having the features of claim 1 and a measuring instrument having the features of claim 9. Preferred embodiments of the invention are set forth in the dependent claims and in the description below, each of which can represent an aspect of the invention either individually or in combination.

According to the present invention, a method for measuring a thread, in particular of a spindle of a ball screw drive, is provided. In the method, a contactless distance sensor is moved parallel to the axial direction of the thread; detecting a measurement signal corresponding to a distance between the distance sensor and an upper side of the thread; detecting an intersection point of the measurement signal having a reference value between a maximum value and a minimum value of the measurement signal; combining two intersection points that follow each other into a first measurement value tuple, and combining two intersection points that follow each other and follow the first measurement value tuple into a second measurement value tuple; calculating a first average value through the intersection points of the first measurement value tuples and calculating a second average value through the intersection points of the second measurement value tuples; and calculating the time-angle resolution from the first average value and the second average value.

Since the measurement of the thread takes place in a non-contact manner, for example by means of ultrasound, and no contact is involved, the measurement process can already be accelerated considerably. In addition, the absolute value of the thread was not measured. Measuring the precise position of the base of the thread is difficult and prone to error. For this purpose, it is also necessary to detect the extremum corresponding to the base in the measurement signal, which requires several calculation steps. The intermediate region between the two threads has a significant extension in the axial direction, so that the measured values corresponding to the intermediate region are in a plateau state. Therefore, the measurement is difficult to resolve. In addition, the start and end points of the intermediate region between subsequent pitches may not be accurately determined, resulting in significant errors in determining the intermediate region. In contrast, in this method, the reference value is used to detect the intersection of the measurement curves generated from the measurement values. If the reference value lies between a maximum value occurring during the measurement and a minimum value occurring during the measurement, the reference value can in principle be selected substantially as desired. Here, it is known that the flanks of the pitch of the thread are substantially symmetrical. This means that the centre point between two points of opposite flanks of the same pitch distributed at the same height corresponds very precisely to the base of the pitch. Likewise, the center point between two points, which are distributed at the same height on flanks of subsequent thread pitches respectively pointing in opposite directions, is very precisely in the center of the intermediate region between the thread pitches. In principle, it does not matter which height of the points on the pitch corresponds to the reference value. In order to determine these center points, the measured values which produce the reference values of the distance sensor are supplied in pairs to measured value tuples, wherein the respective consecutive measured value tuples each have two consecutive measured values which correspond to the reference value and which represent the intersection of the measured value curve with the reference value. The average value is determined by the respective subsequent measurement value tuple. The distance between the first average value and the second average value corresponds to the distance in the axial direction between subsequent thread pitches. In addition, the number of turns of the measured threads is known such that the axial distance between the threads corresponds to a certain rotational angle of the threads (taking the number of turns into account). The thread of the spindle of the ball screw drive is typically a single thread such that a 360 rotation of the spindle corresponds to a feed rate equal to the axial distance of the subsequent thread pitch. In addition, the measurement times of the intersections with the reference values are determined by the measurements of the distance sensors and the measurement curves generated therefrom, and the time intervals between the average values are determined by averaging these measurement times. The time-angle resolution can then be calculated therefrom. For example, if the travel speed and/or travel distance of the distance sensor is also known and/or measured, the thread lead of the thread or other characteristics of the thread can be determined therefrom by means of the calculated time-angle resolution. By measuring the flanks of the pitch of the thread at the same height in a non-contact manner, the properties of the thread can be measured quickly and accurately, enabling a quick measurement of the thread.

The measurement tuples do not overlap. This means that all measured values which form intersections with the reference value are divided into different measured value tuples. In this case, the second measured value tuple follows the first measured value tuple, so that no intersection exists between subsequent measured value tuples which are not assigned to the measured value tuple. This ensures that similar measured values are present in each measured value tuple, which correspond either to the falling flank and the rising flank of the same pitch or to the rising flank and the falling flank of different subsequent pitches. In the case of a multiple-start thread, the measured value tuples assigned to the same thread pitch are preferably compared with one another. Preferably each individual pitch is measured separately, particularly preferably for determining the pitch of the multiple start thread. The ability to quickly measure threads makes it possible, inter alia, to machine threads in multi-spindle automatic lathes and to measure threads during or after machining without significantly increasing the workpiece machining time.

In particular, the measured value is determined as a function of the measurement time starting from the start time or as a function of the axial displacement starting from the start position. With a time-resolved method, a measurement curve determined by the distance sensor can be determined, i.e. the measured values (e.g. voltage) of the distance sensor are plotted as a function of time. Alternatively, a measurement curve can be obtained using a method based on spatial resolution, i.e. the measured values (e.g. voltage) of the distance sensor are plotted as a function of the axial measurement path of the distance sensor. The measured value can be determined more easily from the measurement time if the distance sensor is always moved axially at a constant travel speed. If the travel speed can vary during the measurement, for example due to external disturbances or measurement problems, the measurement accuracy can be maintained more easily if the measured values are determined as a function of the axial displacement.

Preferably, the time-angle resolution is calculated by averaging a plurality of averages from two or more immediately following measurement value tuples. By taking in a plurality of averages of a plurality of measured value tuples, a correspondingly large number of distances between subsequent thread pitches and/or distances between thread pitches spaced by a certain number of measured value tuples can be taken into account. Taking into account a number of averages, the accuracy of the time-angle resolution determined by averaging the averages can be increased.

The respective measured value tuple particularly preferably has an intersection point of the rising flank assigned to a pitch and an intersection point of the falling flank assigned to the following pitch. The mean value of the respective measured value tuples thus corresponds to the center of the intermediate region between two threads following one another in the axial direction. The central region usually has an axial extension which is significantly greater than the thread width, so that measurement errors based on the resolution accuracy of the distance sensor are less pronounced. This improves the measurement accuracy of the thread.

In particular, the measurement of the distance sensor is triggered by a trigger fixed in the longitudinal direction of the thread. This creates a starting point for the measurement of the distance sensor, which is precisely defined in terms of time and/or position. In particular, this allows different measurements of the same thread to be compared with each other and/or with a reference measurement. In addition, it is also possible to measure and verify the axial relative position of the threads or the axial starting point and/or the axial end point of the threads for a given reference value. However, the lead of the thread and/or the lead error may be determined without a fixed trigger.

In particular, the angular displacement of the thread in the circumferential direction relative to a reference angular position of the reference measured thread is calculated from the displacement of the average value relative to the average value of the reference measurement. If the thread to be measured is rotated by an angular amount for the reference measurement, the positioning of the respective thread pitch in the axial direction is slightly offset. This also produces an intersection of the measurement curve with a reference value which produces a phase shift in time and position. This phase shift, in turn, can be used to infer the angular displacement of the thread relative to a reference measurement and/or a reference angular position associated therewith. The undesired angular displacement may be reversed and/or taken into account in a subsequent step. This enables the thread for the ball screw drive to be mounted very precisely in the desired angular position relative to the spindle nut, whereby the accuracy of the ball screw drive can be improved. In particular, this makes it possible to set and/or position a desired angular position during the machining of a thread, in particular of a spindle of a ball screw drive.

Preferably, the travel speed and/or the travel path and/or the travel time of the distance sensor is detected, wherein the thread lead of the thread is calculated by the distance between the first average value and the second average value and/or by the average of the distances between a plurality of successive average values. By taking into account the movement behavior of the distance sensor, further properties of the thread can be measured and verified by means of the measuring curve. In particular, the thread lead and/or pitch can be calculated with multiple start threads.

The thread of the spindle of the ball screw drive is particularly preferably measured. Because the threads are measured and tested accurately, the threads can meet the highest accuracy requirements. This enables threads for ball screw drives to be machined at high production speeds, which is particularly useful for machine tools and high precision applications. The specific linear position of the ball screw drive can be controlled with high accuracy.

The invention further relates to a measuring instrument for measuring a thread, in particular of a spindle of a ball screw drive, having a holding device for holding the thread, a contactless distance sensor which can be moved parallel to the axial direction of the thread, and an evaluation device for evaluating a measurement signal detected by the distance sensor, wherein the evaluation device is used for carrying out the method, which method can be designed and developed as described above. By measuring the flanks of the pitch of the thread at the same height in a non-contact manner, the properties of the thread can be measured quickly and accurately, enabling a quick measurement of the thread.

Drawings

The invention is described hereinafter, by way of example, with reference to the accompanying drawings in which preferred exemplary embodiments are used, wherein the features shown below are capable of representing one aspect of the invention both in isolation and in combination, and wherein:

FIG. 1: a schematic diagram of a measurement curve obtained by a method of measuring a thread is shown.

Detailed Description

The graph shown in fig. 1 shows the measured values of the contactless distance sensor, which represent the voltage (in V) as a function of the measurement time 12 (in s). The measurement values of the distance sensor result in a measurement curve 14 which essentially corresponds to the course of the thread to be measured along the axis. The measurement curve 14 intersects a reference value 16 which lies almost arbitrarily between a maximum and a minimum of the measurement curve 14. The measurement curve 14 intersects the reference value 16 at a first intersection point F_SThe rising flank of the pitch has a positive lead and is at a second intersection F_FThe falling flank of the pitch has a negative lead. Two of themA point of intersection F_SAnd F_FForming a tuple of measured values, whereby the mean value M is calculated, for example, according to the following formula_n：

Where n is the nth considered pitch of the thread. Assuming that a total of N thread pitches are to be considered, which follow each other in the axial direction,

by averaging the considered pitches, a time-angle resolution ZW can be generated for a single thread

In particular for a single-start thread, the thread lead 18 can be determined by the distance between two subsequent averages, for example M_nAnd M_n+1. For greater clarity, the average value M is used in the figures_n-1And M_n-2This is shown by way of example. In addition, the measurement curve 14 may be compared to a reference curve 20. If the thread is rotated by an angular amount with respect to the angular position of the thread of the reference curve 20, the average value MP of the measurement curve 14 can be calculated according to the following formula_nCorresponding mean value MB of reference curve 20_nTime phase difference t between_s：

t_s＝t(MB_n)–t(MP_n)。

Thus, the angular displacement in the circumferential direction between the angular position of the thread of the measurement curve 14 and the angular position of the thread of the reference curve 20 can be determined according to the following formula

Description of the reference numerals

10 voltage 12 measurement time 14 measurement curve 16 referenceValue 18 thread lead 20 reference curve ZW time-angular resolution F_SAscending flank F at intersection_FDescending flank M of intersection_nMean value MP_nAverage value MB of measurement curve_nMean value t of the reference curve_sPhase differenceAngular displacement.