Method for detecting the preload of a linear guide

Abstract

Method for detecting a preload of a linear guide (10) comprising the steps: a) Applying an external force to the linear guide (10) using an external force exerting device, wherein the external force exerting device emits an action signal while the external force is being applied; b) Detecting a technical order-of-magnitude signal with a sensor (20) emitted by the linear guide (10) due to a vibration thereto occurring under the external force; and c) Receiving the action signal of the device exerting an external force and the technical order-of-magnitude signal of the sensor (20), and calculating the preload of the linear guide (10) according to a received result using a signal analyzer (22), wherein the signal analyzer (22) calculates a frequency response function according to a ratio of the action signal of the device exerting an external force to the technical order-of-magnitude signal of the sensor (20) and then calculates the preload of the linear guide (10) according to the frequency response function.

Description

BACKGROUND OF THE INVENTION 1. Technical Field

[0001] The present invention relates to linear guides and in particular to a method for detecting a preload of a linear guide. 2. Description of the state of the art

[0002] A linear guide comprises rolling elements, such as balls or rollers, a carrier, and a rail. The rolling elements rotate within the carrier, allowing the carrier to move along the rail with high precision. Due to friction and collisions between the rail and the rolling elements, the linear guide can vibrate slightly during rapid movement, leading to a reduced service life. In an attempt to overcome the aforementioned disadvantages of the prior art, it is advisable to apply a preload to the linear guide to increase its structural strength and eliminate play.

[0003] To apply a preload to a linear guide, a conventional test procedure involves calculating the friction between the rail and the rolling elements according to the stress required for the support, and then calculating the preload range according to the linear relationship between friction and preload. However, the aforementioned test procedure has the following disadvantage: the friction is subject to errors due to the environment of the linear guide, so the preload calculated in this way is inaccurate. DE 199 40 869 A1 discloses a device with a vibration element that excites a bearing to vibrate. Output signals from sensors for detecting the outer ring vibration of an outer ring are summed over time by an adder and then fed to a transfer function calculation unit.An output signal from a sensor for detecting inner ring vibrations is also supplied to the transfer function calculation unit. This unit calculates a transfer function between the inner and outer rings of the bearing using a fast Fourier transform to determine the vibration mode. A stiffness transformation unit then determines the bearing stiffness based on the resonant frequency. SUMMARY OF THE INVENTION

[0004] One object of the present invention is to provide a method for highly accurate detection of a preload of a linear guide.

[0005] To solve these and other problems, the present invention provides a method for detecting a preload. The method for detecting a preload requires several steps. The first step involves applying an external force to a linear guide by means of a force-exercising device, wherein the force-exercising device emits an operating signal while the external force is being applied. The second step involves detecting a technical order-of-magnitude signal emitted by the linear guide due to the vibration occurring under the external force using a sensor. The technical order-of-magnitude signal can relate to the displacement, velocity, acceleration, or pressure.The third step involves receiving the action signal of the device exerting an external force and the technical magnitude signal of the sensor with a signal analyzer, and calculating a preload of the linear guide according to the obtained result.

[0006] The test method of the present invention thus solves the problems of calculating friction and therefore eliminates the negative effects of environmental factors on the test result, thereby increasing the test precision. BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS Fig. Figure 1 is a structural schematic view of a method for detecting a preload according to an embodiment of the present invention; Fig. Figure 2 is a further structural schematic view of the method for detecting a preload according to the embodiment of the present invention; Fig. Figure 3 is a schematic view of the sequence of the method for detecting a preload according to the embodiment of the present invention; Fig. Figure 4 shows graphs of the results of experiments carried out on three beams that differ in terms of prestress; Fig. Figure 5 shows graphs of the results of experiments carried out on the supports in three different thrust directions; Fig. Figures 6a-6c are structural schematic views of the methods for detecting a prestress according to the present invention, showing three different thrust directions of the supports; Fig. Figure 7 shows graphs of the results of experiments carried out on the same support in three different thrust directions and in two scenarios, i.e., a linear guide that had setup-related errors and a linear guide that was free of setup-related errors; and Fig. Figures 8a-8c are structural schematic views showing three different impact positions of the support. DETAILED DESCRIPTION OF THE FORM OF EXECUTION OF THE INVENTION

[0007] In Fig. 1 comprises a linear guide 10, a rail 12, and a support 14 which is slidably mounted on the rail 12. In Fig. 3 according to the present invention comprises a method for detecting a preload, comprising the steps described below.

[0008] Step a) S1: Applying an external force 14 to the linear guide 10 with an external force-applying device 16, which is operated by a robot arm or manually, wherein the external force-applying device 16 emits an action signal while the external force is being applied. The external force-applying device 16 is a hammer or a shaker, although the present invention is not limited to this. Before the external force-applying device 16 is operated, it is possible to mount the linear guide 10 on a base 18 to prevent the linear guide 10 from being displaced under the influence of the external force applied by the external force-applying device 16. The base 18 is less rigid than the linear guide 10, as in one embodiment of the present invention where the base 18 consists of a sponge to prevent erroneous measurements during the investigations.Alternatively, the base 18 exhibits higher strength than the linear guide 10, as in a variant embodiment of the present invention where the base 18 is made of a conventional lining. The present invention is not limited to the material of which the base 18 is made.

[0009] Step b) S2: Detecting a technical order-of-magnitude signal emitted by the linear guide 10 due to its vibration under the external force by means of a sensor 20. The sensor 20 is an accelerometer, a velocity sensor, a displacement sensor or a microphone, the present invention being no longer limited to these.

[0010] In Fig. In 1, sensor 20 is a piezoelectric accelerometer. Sensor 20 is attached directly to the linear guide 10. The technical magnitude signal emitted by the linear guide 10 due to its vibration under the external force, and detected by sensor 20, relates to the acceleration.

[0011] In Fig. In Figure 2, sensor 20 is a microphone for use in measurement. Sensor 20 is spaced a certain distance from linear guide 10 and is therefore not in contact with it. The technical order-of-magnitude signal emitted by linear guide 10 due to its vibration under external force, and received by sensor 20, relates to sound pressure.

[0012] Step c) S3: Receiving the action signal from the device 16 exerting an external force and a vibration signal from the sensor 20, calculating a frequency response function (FRF) according to the ratio of the action signal to the vibration signal, and calculating the preload of the linear guide 10 according to a frequency change shown by the FRF, using a signal analyzer 22. The ratio of the action signal to the vibration signal is calculated using a denominator, which represents a value obtained as a result of converting the action signal or the vibration signal.

[0013] A transfer function is a mathematical relationship between an input factor and an output result of a phenomenon, when the phenomenon is mathematically described. For example, if we take a mathematical relationship y = ax, where y denotes the output and x is the input, then y / x = a, where a is the mathematical relationship between the output y and the input x, thus providing a transfer function of a control system.

[0014] In Fig. Figure 4 shows graphs of functions that illustrate the results of experiments conducted on beams which were struck three times under different prestress values ​​and in the same position, where each of the three beams has a first prestress value (P1) and a second prestress value (P2), the first prestress value (P1) being greater than the second prestress value (P2). As shown in Fig. As shown in section 4, carriers with the same preload value behave in the same way at the peak value of a natural frequency.

[0015] Fig. Figure 5 shows graphs of functions that show the result of experiments carried out on two beams 14 that differ in their prestress, which were recorded in 3 different tapping directions. Fig. Figure 6a shows that the device 16 exerting an external force taps against the support 14 on its upper surface and shows that the sensor 20 is attached to the lower surface of the rail 12. The result of the experiment, which is shown in Fig. 6a is shown, is Fig. 5 as follows: P3 designates the beam 14 with a small prestress value, and P4 designates the beam 14 with a large prestress value. Fig. Figure 6b shows that the device 16 exerting an external force taps against the support 14 on its upper surface and shows that the sensor 20 is attached to the upper surface of the support 14. The result of the experiment, which is shown in Fig. 6b is explained in Fig. 5 as shown below: P5 designates the beam 14 with a small prestress value, and P6 designates the beam 14 with a large prestress value. Fig. Figure 6c shows that the device 16 exerting an external force taps on the support 14 on a side surface thereof and shows that the sensor 20 is attached to the tapped side surface of the rail 12. The result of the in Fig. The experiment described in 6c is in Fig. Figure 5 shows the following: P7 designates the carrier 14 with a small preload value, and P8 designates the carrier 14 with a large preload value. The tapping direction therefore affects the peak value of the natural frequency (oscillation), although it is also possible to distinguish the difference in preload between two carriers 14.

[0016] Fig. Figure 7 shows graphs of functions that explain the results of experiments performed on the same support at three different tapping positions. The tapping positions are shown in the Fig. Figures 8a-8c show that the external force-exerting device 16 taps the upper surface of the carrier 14 at the left, central, and right positions, with the sensor 20 attached to a lateral surface of the carrier 14, indicating that the peak value of the natural frequency / oscillation is not affected despite different tapping positions on the carrier 14. Fig. 7. The FRF listed above is assigned to the situation where a linear guide has no setup-associated errors, and P9 denotes the peak value of the natural frequency. The FRF listed below is assigned to the situation where a linear guide has setup-associated errors, and P10 denotes the peak value of the natural frequency. As in Fig. Figure 7 shows that the peak value of the natural frequency is not affected, regardless of whether the same linear guide has setup-associated errors or not.

[0017] The test method of the present invention therefore has no problems associated with the calculation of friction and thus excludes the negative effects of environmental factors on the test result, thereby increasing the accuracy of the test.

Claims

[1] Method for detecting a preload of a linear guide (10), comprising the steps of: a) applying an external force to the linear guide (10) with an external force applying device, wherein the external force applying device emits an action signal while the external force is applied; b) detecting with a sensor (20) a technical magnitude signal emitted by the linear guide (10) due to a vibration thereof occurring under the external force; and c) receiving the effect signal of the device applying an external force and the technical magnitude signal of the sensor (20), and calculating the preload of the linear guide (10) according to a received result with a signal analyzer (22), wherein the signal analyzer (22) calculates a frequency response function according to a ratio of the effect signal of the device applying an external force to the technical magnitude signal of the sensor (20) and then calculates the preload of the linear guide (10) according to the frequency response function. [2] The method according to claim 1, wherein before the operation of the external force applying device starts, the linear guide (10) is fixed to a base (18) to prevent the linear guide (10) from displacing under the action of the external force applied by the external force applying device. [3] The method of claim 1, wherein the external force applying device is operated by a robot arm or manually. [4] The method of claim 1, wherein the external force applying device is a percussion hammer. [5] The method of claim 1, wherein the sensor (20) is a piezoelectric accelerometer, and the sensor (20) is mounted directly on the linear guide (10), so that the engineering magnitude signal received by the sensor (20) relates to the acceleration and is emitted by the linear guide (10) due to the vibration occurring upon application of the external force. [6] The method of claim 1, wherein the sensor (20) is a microphone and the sensor (20) is spaced from the linear guide (10) for measurement by a distance such that the engineering magnitude signal received by the sensor (20) relates to sound pressure and is emitted by the linear guide (10) due to the vibration occurring upon application of the external force.

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