Spindle pressure sensing device and pressure sensing method of machine tool

Abstract

In a spindle pressure sensing device and method for a machine tool, a spindle capable of rotating while holding a friction stir welding member is provided in the longitudinal direction at the center of the tip of a spindle housing, and a pressure sensing unit is provided in the circumferential direction between the tip of the spindle housing and the spindle. The pressure sensor is used for detecting the pressure applied to the main shaft in the axial direction.

Description

Technical Field

[0001] This invention relates to a spindle pressure sensing device and method for a machine tool, and more specifically, to a pressure sensing unit and method that uses a pressure sensor mounted on the spindle to detect the pressure applied by the spindle to the workpiece. Background Technology

[0002] Friction stir welding (FSW) involves mounting a friction stir welding component with threaded protrusions on a machine tool spindle. The spindle is rotated at high speed under pressure, thereby generating heat due to friction between the component and the material (workpiece). The frictional heat causes the frictional parts of the component and the material to melt, and the friction surfaces of the component and the material are forced to mix through plastic flow, thus achieving welding.

[0003] The bonding materials used in this type of friction stir welding are mainly lightweight non-ferrous metals (Al, M, Cu, etc.). In addition, this type of friction stir welding requires a relatively strong axial force (pressure), and vibrations are generated due to the stirring action during the rotation of the components used in friction stir welding.

[0004] Therefore, it is crucial to maintain a constant axial pressure applied to the material along the spindle of the machine tool, depending on the material type, thickness, and other processing conditions.

[0005] Therefore, it is necessary to measure the pressure of the component used for friction stir welding by pressing the material through the spindle during the processing; and in order to measure such pressure, a pressure sensor needs to be installed on the spindle.

[0006] As existing technology, refer to Figure 1 ,like Figure 1 As shown in (a), in conventional spindle pressure sensing devices, multiple pressure sensors 4000 that sense vertical applied pressure are inserted and disposed within a sensor ring 3000, which is disposed between the spindle 2000 and the spindle housing 1000.

[0007] Reference Figure 1 (b) Multiple sensors inserted into the sensor ring 3000 configured between the spindle 2000 and the spindle housing 1000 are respectively in a form in which the spindle 2000, the pressure sensor 4000 and the spindle housing 1000 are combined at one time by bolts 5000.

[0008] Thus, in the past, pressure sensing devices, because the main shaft 2000 was ultimately fixed by the bolt portion 5000 that passed through the pressure sensor 4000, had a problem that the bolt portion 5000 could not connect to the pressure sensor 4000 with sufficient tightening force.

[0009] On the other hand, the pressure sensor 4000 should be fixed to the bolt part 5000 with an initial preload within 10 to 20% of the sensing range.

[0010] Furthermore, the preload state of this sensor 4000 must be maintained continuously during the friction stir welding process in order to achieve precise sensing.

[0011] However, if the bolt 5000 is tightened too forcefully to tighten the pressure sensor 4000 with sufficient tightening force, it will exceed the sensing range of the pressure sensor 4000, thus causing another problem of not being able to accurately measure the vertical applied pressure.

[0012] Reference Figure 1 (c) In the past, pressure sensing devices had the following problem: when a large vertical pressure was applied, the pressure sensor 4000 would be compressed, causing the bolt part 5000 to be unable to be fixed, and eventually becoming susceptible to vibration, resulting in the pressure sensor 4000 being unable to be positioned accurately.

[0013] On the other hand, when a large vertical pressure is applied, similarly, in order for the bolts 5000 to tighten the pressure sensor 4000 with sufficient tightening force, more bolt parts 5000 are required, and multiple expensive pressure sensors 4000 need to be configured. Therefore, there have been problems such as increased costs and larger device size due to the configuration of multiple bolt parts 5000 and pressure sensors 4000.

[0014] On the other hand, as prior art, Patent Document 1 relates to a deburring tool for a friction stir welding apparatus, the structure of which includes: a shoulder disposed at the lower end of a main body; a pin disposed at the center of the shoulder, which stirs the pair of base materials by rotation while in contact with a pair of overlapping base materials; and a deburring section attached to one side of the main body for removing burrs generated along the welding line in the upper overlapping base materials. However, Patent Document 1 does not describe a structure for detecting the pressure of the spindle as described in this application.

[0015] Existing technical documents

[0016] Patent documents

[0017] Patent Document 1: Korean Patent No. 10-2433561. Summary of the Invention

[0018] Technical issues

[0019] The object of the present invention for solving the above problems is to fasten the pressure sensing unit installed between the spindle and the spindle housing so that it can have the initial preload required by the spindle and be fastened to the spindle housing with sufficient fastening force, and to improve the measurement accuracy of the pressure applied along the axial direction of the spindle.

[0020] Technical solution

[0021] To address the problems described above, the present invention provides a spindle pressure sensing device for a machine tool, characterized in that it comprises: a spindle rotatably disposed at the center of the front end of a spindle housing, capable of holding a friction stir welding component along its length; and a spindle pressure sensing unit disposed circumferentially between the front end of the spindle housing and the spindle to detect pressure applied axially to the spindle. The pressure sensing unit has an axially elastic, plate-shaped annular ring disposed between the front end of the spindle housing and an upper base. The base is perpendicular to the axial direction and formed circumferentially on the outer periphery of the spindle. Between the elastic ring and the base, a plurality of pressure sensors are circumferentially and equally spaced, secured with a pre-set preload by first fastening bolts. The elastic ring is fixed to the base of the spindle by a plurality of second fastening bolts disposed circumferentially to supplement the fastening force of the elastic ring to the portion other than the portion secured by the first fastening bolts, and is further secured to the spindle housing by a plurality of third fastening bolts disposed circumferentially.

[0022] As a preferred embodiment, the spindle pressure sensing device of the machine tool is characterized in that an anti-loosening nut is tightened at the front end of the first fastening bolt fastened to the base of the spindle.

[0023] As a preferred embodiment, the spindle pressure sensing device of the machine tool is characterized in that a ring plate is provided along the circumferential direction on the upper part of the elastic ring on which the pressure sensor is provided, and the ring plate is fastened to the spindle housing together with the elastic ring by the third fastening bolt.

[0024] As a preferred embodiment, the spindle pressure sensing device of the machine tool is characterized in that the section in the elastic ring in which the pressure sensor is disposed is thinner than the other sections.

[0025] As a preferred embodiment, the spindle pressure sensing device of the machine tool is characterized in that an annular cover ring is provided on the outer edge of the elastic ring in the circumferential direction to protect the spindle housing and the spindle from the outside.

[0026] As a preferred embodiment, the spindle pressure sensing device of the machine tool is characterized in that a spacer is inserted in the circumferential direction between the base and the pressure sensor.

[0027] On the other hand, to solve the problems mentioned above, the present invention provides a spindle pressure sensing method for a machine tool, wherein a spindle capable of rotating and holding a friction stir welding component is disposed at the center of the front end of the spindle housing along the length direction, and a pressure sensing unit is disposed between the front end of the spindle housing and the spindle along the circumferential direction to detect the pressure applied to the spindle axially. The spindle pressure sensing method for a machine tool is characterized in that…

[0028] The axial pressure (F_axial) of the spindle is calculated using the following formula:

[0029] (Mathematical formula) F_axial = m × F_sensor + (2m × F_elactic ring)

[0030] Where m is the number of pressure sensors, F_sensor is the pressure of the pressure sensor installed on the pressure sensing unit, and F_elactic ring is the pressure on the elastic ring.

[0031] On another front, to address the problems described above, the present invention provides a spindle pressure sensing method for a machine tool, wherein a spindle capable of rotating and holding a friction stir welding component is disposed at the center of the front end of the spindle housing along the length direction, and a pressure sensing unit is disposed between the front end of the spindle housing and the spindle along the circumferential direction to detect the pressure applied to the spindle axially. The spindle pressure sensing method for a machine tool is characterized in that…

[0032] The axial pressure (F_axial) of the spindle is calculated using the following formula:

[0033] (numeric expression) F_axial = n × m × F_sensor

[0034] Where n is the error correction constant, m is the number of pressure sensors, and F_sensor is the pressure of the pressure sensor installed on the pressure sensing unit.

[0035] The effects of the invention

[0036] The spindle pressure sensing device of the machine tool of the present invention has the following effects: during friction stir welding, the pressure sensing unit installed between the spindle and the spindle housing can be fastened in a manner that has the initial preload required by the spindle and is fastened to the spindle housing with sufficient fastening force, thereby improving the measurement accuracy of the pressure applied along the axial direction of the spindle, and being sufficiently fastened between the spindle and the spindle housing and maintained.

[0037] Furthermore, the spindle pressure sensing unit of the machine tool of the present invention has less influence on the axial direction of the pressure sensor, while increasing the radial rigidity.

[0038] Furthermore, it can minimize the number of pressure sensors that make up the spindle pressure sensing unit, thereby not only reducing costs but also enabling the miniaturization of the friction stir welding device. Attached Figure Description

[0039] Figure 1 This is a conceptual diagram of a previous machine tool spindle pressure sensing unit.

[0040] Figure 2 This is a partial perspective view of the interior of a machine tool spindle head equipped with a spindle pressure sensing device, according to an embodiment of the present invention.

[0041] Figure 3 This is a partial cross-sectional view of a machine tool spindle head equipped with a spindle pressure sensing device, according to an embodiment of the present invention.

[0042] Figure 4 yes Figure 3 Enlarged view of section A.

[0043] Figure 5 This is an assembly diagram of the pressure sensing unit of the spindle pressure device according to an embodiment of the present invention.

[0044] Figure 6 This is a conceptual diagram of the spindle pressure sensing unit sensing pressure according to an embodiment of the present invention.

[0045] Figure 7 This is an exemplary chart of the present invention, which calculates spindle pressure based on pressure detected by the spindle pressure sensing unit.

[0046] Figure Labels

[0047] 10: Spindle housing, 20: Spindle, 21: Base, 30: Component, 40: Elastic ring, 41: First fastening bolt, 42: Second fastening bolt, 43: Third fastening bolt, 44: Anti-loosening nut, 50: Pressure sensing unit, 51: Pressure sensor, 60: Ring plate, 70: Cover ring, 71: Spacer. Detailed Implementation

[0048] The following reference Figures 2 to 7 Preferred embodiments of the present invention will be described.

[0049] First, refer to Figure 2 and Figure 3 At the front end of the spindle housing 10 of the machine tool, a spindle 20 for holding the friction stir welding component 30 is rotatably arranged along the length direction at the center.

[0050] In addition, a pressure sensing unit 50 for detecting the pressure applied to the spindle 20 along the axial direction is provided at the front end of the spindle housing 10 and between it and the spindle 20.

[0051] The pressure sensing unit 50 functions to sense the pressure applied to the component 30 along the axial direction when the friction stir welding component 30 mounted on the spindle 20 rotates in a state of applying pressure to the workpiece material and performs friction stir welding.

[0052] Such a pressure sensing unit 50 mainly uses a pressure sensor 51, such as a piezoelectric sensor, to detect the axial pressure applied to the spindle 20 during friction stir welding, and feeds back the detected pressure to the control unit (not shown) of the machine tool to control the spindle feed motor (not shown) of the spindle 20. This helps to control the spindle 20 to maintain a constant pressure along the axial direction toward the workpiece material, thereby enabling the friction stir welding component 30 to perform friction stir welding on the workpiece material with good quality.

[0053] like Figures 3 to 5 As shown, the pressure sensing unit 50 has a plate-shaped annular elastic ring 40 between the front end of the spindle housing 10 and the upper part of the base 21 formed on the outer periphery of the spindle 20 at a right angle to the axial direction and along the circumferential direction. The annular elastic ring 40 is elastic in the axial direction.

[0054] A plurality of pressure sensors 51 are disposed between the elastic ring 40 and the base 21, and each pressure sensor 51 is fastened between the elastic ring 40 and the base 21 with a preset preload by a first fastening bolt 41. At this time, the preload of the first fastening bolt 41 is set within the range of the initial required preload applied to the pressure sensor 51.

[0055] In this way, by tightening the pressure sensor 51 within the initial pre-pressure range of approximately 10 to 20% of the sensing pressure range, the detection accuracy of the pressure sensor 51 can be improved.

[0056] This is to overcome the problem that the detection accuracy of pressure sensor 51 decreases when it is tightened with pressure exceeding the initial required pre-pressure range during the tightening process.

[0057] On the other hand, the pressure sensors 51 are arranged at equal intervals along the circumference of the elastic ring 40, and three pressure sensors are provided in this embodiment.

[0058] Tighten the anti-loosening nut 44 at the front end of the first fastening bolt 41, which is fastened to the base 21 of the main shaft 20, to prevent the first fastening bolt 41 from loosening.

[0059] Furthermore, the elastic ring 40 is fixed to the base 21 of the spindle 20 by the first fastening bolt 41, but with a weaker fastening force equivalent to the initial preload applied to the pressure sensor 51. Therefore, in order to supplement the fastening force, in addition to the portion that is fastened by the first fastening bolt 41, it is further fixed to the base 21 of the spindle 20 in the circumferential direction by a plurality of second fastening bolts 42.

[0060] Thus, the spindle 20, which has its own weight in the initial assembly state, is fixed to the elastic ring 40 with sufficient fastening force.

[0061] Furthermore, the elastic ring 40 is fastened to the spindle housing 10 by a plurality of third fastening bolts 43 arranged along the circumferential direction, thereby making the spindle 20, pressure sensor 51 and spindle housing 10 connected in series.

[0062] On the other hand, a ring plate 60 is provided in the circumferential direction above the elastic ring 40 where the pressure sensor 51 is located. The ring plate 60 is fastened to the spindle housing 10 together with the elastic ring 40 by the third fastening bolt 43.

[0063] The ring plate 60 serves as a space for elastic deformation of the circumferential elastic ring 40 portion without pressure sensor 51 when axial pressure is applied to the main shaft 20, and can be structurally integrated with 40.

[0064] On the other hand, in the elastic ring 40, the section where the pressure sensor 51 is provided between adjacent second fastening bolts 42 is formed to be thinner than the section where the second fastening bolts 42 are fastened. As a result, when axial pressure is applied to the spindle 20, the portion of the elastic ring 40 where the pressure sensor 51 is provided undergoes elastic deformation even under a small pressure. Therefore, while being sufficiently rigid for radial forces on the spindle 20, the thinner thickness can improve the sensitivity of the pressure sensor 51 for axial pressure on the spindle 20.

[0065] On the other hand, an annular cover ring 70 is provided on the outer edge of the elastic ring 40 in the circumferential direction, which protects the elastic ring 40 between the spindle housing 10 and the spindle 20 from external influences.

[0066] Furthermore, a spacer 71 can be inserted circumferentially between the base 21 of the spindle 20 and the pressure sensor 51. The spacer 71 manages the assembly tolerance between the upper surface of the base 21 and the pressure sensor 51, thereby accurately transmitting the axial pressure applied from the base 21 to the pressure sensor 51.

[0067] The following refers to the accompanying diagrams illustrated above and Figures 6 to 7The calculation process for calculating the pressure applied to the main shaft 20 along the axial direction using the pressure sensing unit 50 is explained.

[0068] In addition, such as Figure 6 As shown, when the friction stir welding component 30 is held at the front end of the spindle 20 and rotated at high speed, pressure is applied to the workpiece material and friction stir welding is performed. The axial pressure F_axial of the spindle 20 transmitted through the component 30 to the spindle 20 functions as the sensor pressure F_sensor applied to each pressure sensor 51 of the pressure sensing unit 50 through the base 21 and spacer 71 of the spindle 20. Therefore, including the pressure F_elactic ring on the elastic ring 40, the axial pressure F_axial of the spindle 20 can be expressed as Equation 1 below.

[0069] (Equation 1) F_axial = m × F_sensor + (2m × F_elactic ring)

[0070] Where m is the number of pressure sensors 51.

[0071] On the other hand, such as Figure 7 As shown, the elastic ring 40 is designed such that the pressure (2m × F_elatic ring) on ​​the elastic ring 40, except for the part where the pressure sensor 51 is set, is much smaller than the overall axial pressure F_axial on the spindle 20. However, there is a slight difference between the axial pressure F_axial on the spindle 20 and the pressure (m × F_sensor) sensed by the m pressure sensors 51.

[0072] To correct for this discrepancy, as shown in Equation 2 below, the error correction value n obtained through repeated measurements can be used to more accurately calculate the total axial pressure F_axial on the spindle 20.

[0073] (Formula 2) F_axial = n × m × F_sensor

[0074] Where n is the error correction constant.

[0075] Thus, the spindle pressure sensing device of the machine tool of the present invention has the following effect: the pressure sensing unit 50 installed between the spindle 20 and the spindle housing 10 during friction stir welding can be fastened in a manner that has the initial preload required by the spindle 20 and is fastened to the spindle housing 10 with sufficient fastening force, thereby improving the measurement accuracy of the pressure applied along the axial direction of the spindle 20 and fastening it to the spindle 20 and the spindle housing 10 with sufficient fastening force.

[0076] Furthermore, the spindle pressure sensing device of the machine tool of the present invention is less affected by the axial direction of the pressure sensor 51, while the radial rigidity is increased.

[0077] Furthermore, the number of pressure sensors 51 constituting the spindle pressure sensing device can be minimized, thereby not only reducing costs but also enabling the miniaturization of the friction stir welding device.

[0078] Although the invention has been described above with reference to preferred embodiments, those skilled in the art or with ordinary knowledge in the field will understand that various modifications and alterations can be made to the invention without departing from the spirit and technical field defined by the claims. Therefore, the scope of the invention should not be limited to the contents described in the detailed specification, but should be defined by the claims.

Claims

1. A spindle pressure sensing device for a machine tool, characterized in that, include: The spindle is arranged at the center of the front end of the spindle housing, and is able to hold the friction stir welding component and rotate it along the length direction; as well as A spindle pressure sensing unit is disposed circumferentially between the front end of the spindle housing and the spindle to detect the pressure applied axially to the spindle. The pressure sensing unit has a plate-shaped annular elastic ring that is elastic in the axial direction between the front end of the spindle housing and the upper part of the base. The base is perpendicular to the axial direction and is formed along the circumferential direction on the outer periphery of the spindle. Between the elastic ring and the base, multiple pressure sensors are equally spaced along the circumferential direction and fastened with a pre-set preload using a first fastening bolt. The elastic ring is fixed to the base of the spindle by a plurality of second fastening bolts arranged in a circumferential direction to supplement the fastening force of the elastic ring to the portion other than the portion fastened by the first fastening bolt, and is fastened to the spindle housing by a plurality of third fastening bolts arranged in a circumferential direction.

2. The spindle pressure sensing device for a machine tool according to claim 1, characterized in that, Tighten the anti-loosening nut at the front end of the first fastening bolt that is fastened to the base of the spindle.

3. The spindle pressure sensing device for a machine tool according to claim 1, characterized in that, A ring plate is provided on the upper part of the elastic ring where the pressure sensor is located, along the circumferential direction. The ring plate is fastened to the main shaft housing together with the elastic ring by the third fastening bolt.

4. The spindle pressure sensing device for a machine tool according to claim 1, characterized in that, In the elastic ring, the section where the pressure sensor is located is formed to be thinner than the other sections.

5. The spindle pressure sensing device for a machine tool according to claim 1, characterized in that, An annular cover ring is provided on the outer edge of the elastic ring in the circumferential direction to protect the spindle housing from external contact with the spindle.

6. The spindle pressure sensing device for a machine tool according to claim 1, characterized in that, A spacer is inserted circumferentially between the base and the pressure sensor.

7. A method for sensing spindle pressure in a machine tool, wherein, A spindle capable of holding and rotating friction stir welding components is disposed at the center of the front end of the spindle housing along its length. A pressure sensing unit is disposed between the front end of the spindle housing and the spindle along the circumferential direction to detect the pressure applied to the spindle axially. The spindle pressure sensing method of the machine tool is characterized in that... The axial pressure (F_axial) of the spindle is calculated using the following formula: (Mathematical formula) F_axial = m × F_sensor + (2m × F_elactic ring) in, m represents the number of pressure sensors. F_sensor represents the pressure of the pressure sensor located on the pressure sensing unit. F_elactic ring represents the pressure exerted on the elastic ring.

8. A method for sensing spindle pressure in a machine tool, wherein, A spindle capable of holding and rotating friction stir welding components is disposed at the center of the front end of the spindle housing along its length. A pressure sensing unit is disposed between the front end of the spindle housing and the spindle along the circumferential direction to detect the pressure applied to the spindle axially. The spindle pressure sensing method of the machine tool is characterized in that... The axial pressure (F_axial) of the spindle is calculated using the following formula: (numeric expression) F_axial = n × m × F_sensor in, n is the error correction constant. m represents the number of pressure sensors. F_sensor is the pressure of the pressure sensor set on the pressure sensing unit.

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