Stress detection device

Abstract

To realize a stress detection device capable of detecting stress with high sensitivity and highly accuracy, obtaining stable detection values by reducing detection noise, and being incorporated into a system while suppressing an increase in size.SOLUTION: A stress detection device 100 includes a bearing portion 106 that pivotally supports an external force receiver 105, a support frame 100A that supports the external force receiver through the bearing portion, and a torque detection structure 100B that detects torque in a rotational direction. The torque detection structure includes: an elastic deformation body 117 for torque detection which extends from a fixed portion located on one side of an axis to the other side of the axis, has a displacement portion at an intermediate position, and in which a region between the fixed portion and the displacement portion is configured to be elastically deformable in the rotational direction; a deformation detector 127 for torque detection which detects an amount of elastic deformation; and external force transmission portions 111, 112 for torque detection which are connected to the external force receiver in the rotational direction and come into contact with the displacement portion in the rotational direction.SELECTED DRAWING: Figure 9

Description

[Technical Field]

[0001] The present invention relates to a stress detection device. [Background technology]

[0002] Conventionally, there has been known a machining device that, when machining an object with a tool such as a drill or a cutting tool in a machine tool, detects cutting resistance such as excessive torque or thrust load that the tool receives from the object, and controls the machining operation so that excessive load is not applied to the tool (see, for example, Patent Document 1 below).

[0003] Some of the above-mentioned machining devices are configured to detect the load on the tool by providing a sensor in the bearing portion of the spindle. For example, there is a spindle equipped with sensors that detects cutting resistance by providing a radial sensor and a thrust sensor made of a highly rigid material in the bearing portion of the spindle (see, for example, Patent Document 2 below). Also proposed is a tool holder that can detect both torque and thrust load overloads by detecting the relative rotation between the tool holder barrel and the holder shaft (see, for example, Patent Document 3 below).

[0004] Furthermore, a cutting dynamometer has been reported to prevent breakage of a micro-diameter drill when machining (see, for example, Non-Patent Document 1). In this report, by using a strain gauge and an air hydrostatic bearing structure, it is possible to measure the minute cutting resistance in order to prevent breakage of an extremely thin drill with a diameter of 0.1 mm or less. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2001-341014 [Patent Document 2] Specification of Unexamined Utility Model Application Publication No. 3-47748 [Patent Document 3] Special Publication No. 7-41520 [Non-patent literature]

[0006] [Non-Patent Document 1] "Development of a cutting dynamometer for micro-drilling using strain gauges and an air hydrostatic bearing structure" Ryoichi Arai et al., Journal of the Japan Society for Abrasive Technology, Vol. 56, No. 6, 2012 JUN. 408-413 Summary of the Invention [Problem to be solved by the invention]

[0007] However, when detecting cutting resistance using a sensor provided on the conventional spindle to prevent excessive load from being applied to the tool, the torque and thrust load must be detected while transmitting the driving force required for cutting to the tool and ensuring sufficient rigidity to withstand the torque and thrust load applied to the tool by cutting. Therefore, since it is theoretically impossible to generate a displacement sufficient to accurately detect the load itself, the conventional detection method has a problem of insufficient detection accuracy. In particular, it is extremely difficult to accurately detect slight loads required to prevent damage to tools such as thin drills with diameters of several millimeters or less. Therefore, there is a problem that accurate detection requires sacrificing the rigidity of the spindle and processing accuracy.

[0008] Furthermore, with the above-mentioned conventional detection structures, the detection sensitivity is highly dependent on the structure of the spindle and the structure of the detection unit (their rigidity), making it impossible to detect the absolute magnitude of torque or thrust load. Furthermore, if the spindle or detection unit has a different structure, different detection characteristics will be exhibited, which makes it difficult to deal with overload in a unified manner, as it is necessary to investigate in advance the relationship between the detection value and the tool load for each spindle and machine tool.

[0009] Furthermore, although the report in the above-mentioned Non-Patent Document 1 is capable of detecting weak cutting resistance, the detection value is significantly affected by noise such as vibration, making it difficult to obtain a stable detection value. In addition, the device structure is large, making it difficult to incorporate into existing systems such as actual processing devices.

[0010] Therefore, the present invention solves the above problems, and its object is to realize a stress detection device that detects stress when subjected to an external force, which is capable of detecting stress with high sensitivity and high accuracy, can reduce detection noise to obtain stable detection values, and can be incorporated into a system without increasing in size. [Means for solving the problem]

[0011] In order to achieve the above object, the stress detection device of the present invention comprises an external force receptor that receives an external force directly or indirectly, a bearing portion that supports the external force receptor in a radial direction, a support frame that supports the external force receptor via the bearing portion, and a torque detection structure that detects torque in a rotational direction about the axis of the external force receptor, wherein the torque detection structure comprises an elastically deformable body for torque detection that has a fixed portion attached to the support frame at a position on one side of the axis of the external force receptor, extends from the fixed portion to the other side of the axis, and has a displacement portion at a position on the other side, and is configured so that the region between the fixed portion and the displacement portion is elastically deformable in the rotational direction, a torque detection deformation detector that detects the amount of elastic deformation of the region of the elastically deformable body for torque detection, and a torque detection external force transmission portion that is connected to the external force receptor in the rotational direction and abuts against the displacement portion in the rotational direction.

[0012] According to the present invention, when an external force is applied to the external force receptor, causing a rotational displacement of the external force receptor journaled by the bearing, the rotational component of the external force is transmitted by the torque-detecting external force transmission section to the displacement section of the elastically deformable body for torque detection, causing the region between the fixed section and the displacement section to elastically deform in the rotational direction. This elastic deformation is detected by the torque-detecting deformation detector, allowing the stress corresponding to the rotational torque caused by the external force to be detected. This minimizes frictional resistance by journaling the bearing section in the radial direction, making it possible to detect weak torque with high sensitivity and accuracy based on the amount of elastic deformation. In particular, because the elastically deformable body for torque detection extends from one side of the axis of the external force receptor to the other, the elastic deformation region of the elastically deformable body for torque detection can be set to a wide range, thereby improving detection sensitivity and detection accuracy while reducing the size of the torque detection structure.

[0013] In the present invention, it is preferable that the torque detection elastically deformable body is attached so that the fixed portion and the displacement portion are arranged one above the other and extend vertically downward from the fixed portion. In this way, the amount of elastic deformation in the region between the fixed portion and the displacement portion of the torque detection elastically deformable body is less affected by the weight of the torque detection elastically deformable body, making it possible to detect stress corresponding to torque caused by external force with even higher sensitivity and accuracy.

[0014] In the present invention, it is preferable that the displacement portion of the elastically deformable body for torque detection is a free end, which makes it difficult for the elastic deformation of the region to be hindered by the contact of the external force transmission portion for torque detection, thereby enabling the detection of stress corresponding to torque with even higher sensitivity and accuracy.

[0015] In the present invention, it is preferable that the torque detection structure further includes a holding member that holds the displacement portion in a direction opposite to the direction of contact of the external force transmission portion for torque detection and that applies a holding force that prevents the displacement portion from separating from the external force transmission portion for torque detection. This suppresses vibration of the elastically deformable body for torque detection caused by vibration in the rotational direction of the external force receptor, and prevents detection failure of the stress corresponding to torque due to vibration or other noise.

[0016] In the present invention, it is preferable that the torque detection structure further includes a reference body for torque comparison that is made of the same material, has the same shape and dimensions, and is installed in the same orientation as the elastically deformable body for torque detection, and a deformation detector for torque comparison that detects the amount of elastic deformation in a region of the reference body for torque comparison that corresponds to the region of the elastically deformable body for torque detection. This makes it possible to reduce the effects of temperature, vibration, and the like on the detected values ​​by comparing the detected values ​​of the deformation detector for torque detection and the deformation detector for torque comparison and outputting the comparison result, such as a differential signal. Here, it is preferable that the elastically deformable body for torque detection and the reference body for torque comparison are arranged along the axis. According to this, by arranging the elastically deformable body for torque detection and the reference body for torque comparison, which are made of the same material, have the same shape and dimensions, and have the same posture, along the axis of the external force receptor, the positional relationship around the axis relative to the external force receptor between the elastically deformable body for torque detection and the reference body for torque comparison becomes equivalent, and they are equally subjected to vibrations in the rotational direction of the external force receptor.As a result, the elastically deformable body for torque detection and the reference body for torque comparison are in a relationship that is convenient for canceling out noise such as vibrations when detecting torque in the rotational direction, and it becomes possible to detect torque with even greater sensitivity and accuracy.

[0017] In the present invention, it is preferable that the bearing portion has a thrust direction support portion that supports the external force receptor in the thrust direction, and further includes a thrust load detection structure that detects stress corresponding to an axial thrust load along the axis of the external force receptor, and the thrust load detection structure includes: an elastic deformation body for thrust load detection, which has a pair of fixed portions on both sides of the axis of the external force receptor, attached to the support frame, extending between the pair of fixed portions and including a displacement portion located in the vicinity of the axis therebetween, and wherein the regions between the pair of fixed portions and the displacement portions are configured to be elastically deformable in the axial direction; a thrust load detection deformation detector that detects the amount of elastic deformation of the regions of the elastic deformation body for thrust load detection; and an external force transmission portion for thrust load detection that faces the external force receptor in the axial direction via the thrust direction support portion and abuts the displacement portion in the axial direction. According to this, an elastic deformation body for detecting thrust loads is provided which has a pair of fixed portions on both sides of the axis of the external force receptor and a displacement portion located in the vicinity of the axis, and an external force transmission portion for detecting thrust loads which faces the external force receptor via a support portion in the thrust direction abuts against the displacement portion, thereby making it possible to detect stress corresponding to the thrust load of the external force receptor caused by an external force in a stable manner with high sensitivity and high accuracy.

[0018] In the present invention, it is preferable that the thrust load detection structure further includes a reference body for thrust load comparison that is made of the same material, has the same shape and dimensions, and is installed in the same orientation as the elastically deformable body for thrust load detection, and a deformation detector for thrust load comparison that detects the amount of elastic deformation in a region of the reference body for thrust load comparison that corresponds to the region of the elastically deformable body for thrust load detection. This makes it possible to reduce the effects of temperature, vibration, and the like on the detection values ​​by using the comparison result between the deformation detector for thrust load detection and the deformation detector for thrust load comparison. Here, it is preferable that the elastically deformable body for thrust load detection and the reference body for thrust load comparison are arranged along a plane perpendicular to the axis. According to this, by arranging the elastically deformable body for thrust load detection and the reference body for thrust load comparison, which are made of the same material, have the same shape and dimensions, and have the same attitude, along a plane perpendicular to the axis of the external force receptor, the axial positional relationship between the elastically deformable body for thrust load detection and the reference body for thrust load comparison with respect to the external force receptor becomes equivalent, and they are also equally subjected to axial vibrations of the external force receptor.As a result, the elastically deformable body for thrust load detection and the reference body for thrust load comparison are in a relationship that is convenient for canceling out noise such as vibrations when detecting thrust loads, and it becomes possible to detect stress corresponding to thrust loads with even greater sensitivity and accuracy.

[0019] In the present invention, the elastically deformable body for detecting thrust loads preferably extends between the pair of fixed portions and includes two sets of elastically deformable portions having the displacement portion therebetween, on both sides along a direction perpendicular to the direction connecting the pair of fixed portions with respect to the axis. Thus, in the elastically deformable body for detecting thrust loads, two sets of elastically deformable portions, each including a pair of fixed portions and a displacement portion, are provided on both sides of the axis, thereby enabling more balanced detection of axial displacement of the external force receptor. For example, by arranging a pair of fixed portions above and below and providing elastically deformable portions having intermediate displacement portions on the left and right sides of the axis, detection of stress corresponding to thrust loads can be performed in a balanced manner with high sensitivity and accuracy by a support structure from above, below, left, and right. It is preferable that a deformation detector for detecting thrust loads is provided on each of the two sets of elastically deformable portions. Thus, by using the detection values ​​of each deformation detector in combination, even more sensitive and accurate stress detection can be performed in a stable state. [Effects of the Invention]

[0020] According to the present invention, it is possible to realize a stress detection device that can detect slight stress caused by external force, improve the stress detection sensitivity and detection accuracy, and stably obtain detection values ​​corresponding to external force.

[0021] In particular, by setting the area between the fixed portion and the displacement portion in a range extending from one side of the axis of the external force receptor to the other side of the elastic deformation body for torque detection, the elastic deformation area of ​​the elastic deformation body for torque detection can be set over a wide range, thereby increasing the detection sensitivity and detection accuracy while reducing the size of the torque detection structure. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a front perspective view showing an embodiment of a stress detection device according to the present invention as viewed obliquely from the front. [Figure 2] FIG. 2 is a rear perspective view showing the embodiment as viewed from diagonally rearward. [Figure 3] FIG. [Figure 4] FIG. [Figure 5] FIG. 2 is a partial front perspective view showing the state in which a part of the support frame is removed according to the embodiment. [Figure 6] FIG. 2 is a partial rear perspective view showing the state in which a part of the support frame is removed according to the embodiment. [Figure 7] FIG. 2 is a partial rear perspective view showing the measurement structure of the embodiment. [Figure 8] FIG. 2 is a partially transparent rear perspective view of the torque detection structure according to the embodiment; [Figure 9] FIG. 2 is a partial rear perspective view showing the embodiment with a part of the support frame removed and the thrust load detection structure omitted. [Figure 10] FIG. 2 is a partial rear perspective view showing the embodiment with a portion of the support frame removed and a torque detection structure omitted. [Figure 11] FIG. 2 is a side view showing the workpiece table, torque detection structure, and thrust load detection structure, with the support frame omitted. [Figure 12] FIG. 3 is a partial cross-sectional view schematically showing a bearing structure of the workpiece table. [Figure 13] 1A and 1B are a plan view and a longitudinal sectional view, respectively, showing a method for calibrating the detection values ​​of an elastic deformation body for torque detection and a deformation detector for torque detection using a detection value calibration jig. [Figure 14] 1A and 1B are a plan view and a longitudinal cross-sectional view showing a method for calibrating the detection values ​​of an elastic deformation body for detecting thrust loads and a deformation detector for detecting thrust loads using a detection value calibration jig; DETAILED DESCRIPTION OF THE INVENTION

[0023] Next, an embodiment of a stress detection device according to the present invention will be described in detail with reference to the accompanying drawings. As shown in Fig. 12, a stress detection device 100 according to an embodiment of the present invention is an apparatus configured to measure the torque in the rotational direction and the thrust load in the axial direction that the workpiece T is subjected to by using a torque detection structure and a thrust load detection structure to detect stress that occurs when a workpiece table 104, which fixes a workpiece T that is the target of a machining process such as cutting in a machine tool, receives an external force from a tool S such as a drill. The measured torque and thrust load can be directly regarded as the torque load and thrust load that the tool S, such as a drill, receives.

[0024] The stress detection device 100 comprises a gate-shaped support frame 100A as a whole, which includes a main support plate 101 at the front and left and right support side plates 102 and 103 fixed to the main support plate 101. The stress detection device 100 is primarily used in the position shown in FIGS. 1 and 2 , and is not limited to this position. However, the orientation and position of each component in the illustrated position will be used in the description of the various components. In the illustrated example, a workpiece table 104 is provided on which a workpiece T is mounted. The workpiece table 104 is connected and fixed to a front end 105a of an external force receptor 105 shown in FIGS. 11 and 12 . The external force receptor 105 is generally axially shaped and is mounted in a position extending horizontally. The workpiece table 104 may be of any shape and may be integrally formed with the external force receiver 105, but when used as the workpiece table 104 of a machine tool, it is desirable that it be equipped with a gripping structure such as a chuck for gripping the workpiece T.

[0025] Hydrostatic bearings 106, 107 are attached to main support plate 101. These hydrostatic bearings support external force receptor 105 so that it can rotate freely around axis 105x and hold it in the axial direction along axis 105x. Radial support 106 of the hydrostatic bearings radially supports external force receptor 105 so that it can rotate freely in the rotation direction. Thrust support 107 of the hydrostatic bearings includes thrust support portions 107A and 107B that support flange-shaped thrust plate 105b provided on external force receptor 105 by sandwiching the thrust support portion 107A from both sides in the axial direction, with front thrust support portion 107A fixed to main support plate 101 and rear thrust support portion 107B fixed to elastically deformable body 108, which will be described later. Note that Figure 12 shows a schematic illustration of a hydrostatic bearing structure in which fluids such as air, other gases, and liquids are introduced from fluid introduction portions 106a, 107a, and 107b to opposing locations inside in the radial and thrust directions, but is not limited to the illustrated example.

[0026] As shown in Fig. 12, the hydrostatic bearing portion consisting of radial support portion 106 and thrust support portion 107 supports external force receptor 105 in both the radial and thrust directions using a hydrostatic bearing structure. For example, it is preferable to support external force receptor 105 rotatably around axis 105x using a gas bearing structure such as air. The specific structure (throttle structure, etc.) of the hydrostatic bearing is not particularly limited, but it is preferable to have an inherent throttle structure with a number of holes in opposing locations.

[0027] In the support frame 100A, a space surrounded by the main support plate 101 and the left and right support side plate portions 102, 103 is provided with a torque detection structure 100B connected to the external force receptor 105 as shown in Fig. 9, and a thrust load detection structure 100C as shown in Fig. 10. Here, Fig. 9 shows the structure without the components of the thrust load detection structure 100C, and Fig. 10 shows the structure without the components of the torque detection structure 100B.

[0028] 9, torque detection structure 100B includes connecting member 111, which is a bracket fastened and fixed to rear end portion 105c of external force receptor 105 shown in Fig. 12, transmission member 112 fixed to connecting member 111, and elastically deformable body 117 for torque detection that is elastically deformed by tip end portion 112a (see Fig. 8) of transmission member 112. Connecting member 111 extends downward from axis 105x of external force receptor 105 in the figure, and transmission member 112 is attached to the portion of connecting member 111 that extends downward in the figure, and transmission member 112 extends further downward in the figure, with tip end portion 112a abutting against tip end portion 117a, which is a displacement portion of elastically deformable body 117 for torque detection, in the direction of rotation about axis 105x. The elastically deformable body 117 for torque detection is a strip-shaped plate-like body extending in the vertical direction in the figure, and has a fixed portion at its upper end attached to a beam 101c that is attached to the main support plate 101 and extends rearward, with the body hanging downward in the figure. A reference body 118 for torque comparison, which is a strip-shaped plate-like body made of the same material and having the same shape and dimensions as the elastically deformable body 117 for torque detection, is arranged in parallel to the beam 101c in an axially aligned manner in the same position as the elastically deformable body 117 for torque detection. The connecting member 111 and the transmission member 112 constitute the above-mentioned "external force transmission unit for torque detection."

[0029] Here, the plate surface of the elastically deformable body 117 for torque detection has an orientation perpendicular to the rotation direction, and is therefore configured to be elastically deformable in the rotation direction. A strain sensor 127 is attached between a fixed portion, which is the upper end of the elastically deformable body 117 for torque detection attached to the beam 101c, and a displacement portion with which the tip end 112a of the transmission member 112 abuts. This strain sensor 127 is the above-mentioned "torque detection deformation detector" that detects the amount of elastic deformation in the region between the fixed portion (upper end) and the displacement portion (lower end or tip end 112a) of the elastically deformable body 117 for torque detection. In addition, a strain sensor 128 of the same type (corresponding to the above-mentioned "torque comparison deformation detector") is attached to the reference body 118 for torque comparison at the same position as the strain sensor 127 of the elastically deformable body 117 for torque detection. By outputting the comparison result such as the difference between the detected values ​​of the strain sensors 127 and 128, it is possible to derive stress (torque) while suppressing the influence of temperature on the detected values ​​and the influence of noise such as machining vibrations. Note that all of the strain gauges in this embodiment can be configured as semiconductor strain gauges or the like.

[0030] When workpiece T is attached to workpiece table 104 and is subjected to drilling or other processing by tool S, such as a small-diameter drill, attached to a spindle (not shown), connecting member 111 is set so that tip end 112a of transmission member 112 abuts against elastically deformable body 117 for torque detection in the rotation direction in which external force receptor 105 receives an external force (processing load) from tool S. Normally, if tool S is a drill, it drills holes by rotating clockwise, so the torque received from tool S is applied clockwise when viewed from the front side of external force receptor 105. Therefore, tip end 112a of transmission member 112 also abuts against elastically deformable body 117 for torque detection in the same rotation direction around axis 105x.

[0031] Here, elastically deformable body 117 for torque detection and reference body 118 for torque comparison are both arranged in an orientation such that their plate surfaces (surfaces perpendicular to the direction of elastic deformation) face the rotation direction about axis 105x of external force receptor 105, and are arranged in the axial direction along axis 105x, with the same material, shape and dimensions, and the same orientation. As a result, elastically deformable body 117 for torque detection and reference body 118 for torque comparison are both arranged in an orientation suitable for primarily detecting the torque of external force receptor 105, and are also arranged so as to have an equivalent positional relationship with respect to external force receptor 105 in the rotation direction about the axis along which torque is detected. For this reason, elastically deformable body 117 for torque detection and reference body 118 for torque comparison are configured so as to be equally affected by noise elements, such as vibrations in the rotation direction about the axis, among the influences received from external force receptor 105 when detecting torque. Therefore, by outputting comparison results such as the difference or ratio of the detected values ​​of the deformation detector 127 for torque detection and the deformation detector 128 for torque comparison, it is possible to reduce the effects of temperature and noise on the detected torque values.

[0032] On the other hand, a tip end 113a of a holding member 113 is configured to abut against elastically deformable body 117 for torque detection in the opposite rotation direction to the abutment direction of tip end 112a of transmission member 112. By abutting tip end 113a of holding member 113 in the opposite direction, it is possible to suppress vibration of elastically deformable body 117 due to the abutment of transmission member 112. This holding member 113 is attached rotatably in the rotation direction by a support shaft 115 attached inside connecting member 111 shown in a transparent form in Fig. 8, and is elastically held by an elastic member 114 such as a leaf spring whose upper end is attached to connecting member 111 so that tip end 113a of holding member 113 does not rotate in a direction away from elastically deformable body 117.

[0033] With the above configuration, when the workpiece T is subjected by the tool S to torque in the contact direction of the tip end 12a of the transmission member 112 against the elastic deformable body 117, it is possible to prevent problems such as vibrations caused by machining that also vibrate the elastic deformable body 117 for torque detection, hindering the signal output and detection accuracy of the strain sensor 127. In particular, vibrations at the tip end of the elastic deformable body 117 for torque detection that are caused by the contact force of the transmission member 112 are absorbed by the elastic force of the elastic member 114, making it easier to detect minute torques. Furthermore, by adjusting the elastic characteristics of the elastic member 114, it is possible to appropriately set the degree of suppression of the effects of machining vibrations, prevention of resonance, and other effects.

[0034] On the other hand, the thrust load detection structure 100C has an elastically deformable body 108 for thrust load detection that is a fixed part having its upper and lower ends attached to the main support plate 101 and has a displacement part midway between the upper and lower parts attached to the rear thrust support part 107B, and a reference body 109 for thrust load comparison that has its upper and lower ends attached to the main support plate 101 in the same way as the elastically deformable body 108 for thrust load detection. Here, the elastically deformable body 108 for thrust load detection is made of a band-like plate-like body that is configured in the shape of a rectangular frame in a plan view when viewed from the rear, and main parts of the torque detection structure 100B are provided to penetrate without contact through a central opening in a plan view of the elastically deformable body 108 for thrust load detection so that the connecting member 111, transmission member 112, beam member 101c, etc., connected to the external force receptor 105, protrude rearward. The thrust support portion 107B constitutes an "external force transmission portion for detecting thrust load" that transmits the external force from the external force receptor 105 to the displacement portion of the elastic deformation body 108 for detecting thrust load.

[0035] Here, the plate surface of the elastically deformable body 108 for thrust load detection is a surface having an orientation perpendicular to the axial direction, and therefore the elastically deformable body 108 is configured to be elastically deformable in the axial direction. The elastically deformable body 108 for thrust load detection has two vertically extending band-like portions (corresponding to the above-mentioned "two sets of elastic deformation portions") on the left and right of the rectangular frame-shaped portion, respectively, to which a strain sensor 138 (corresponding to the above-mentioned "deformation detector for thrust load detection") is attached, thereby alleviating the bias between the left and right of the amount of elastic deformation in the middle portion above and below the elastically deformable body 108 and improving the detection sensitivity and detection accuracy. Note that the reference body 109 for thrust load comparison is not frame-shaped, but is a single band-shaped plate-like body that extends vertically in parallel with the elastically deformable body 108, and has a strain sensor 139 (corresponding to the above-mentioned "deformation detector for thrust load comparison") attached at a position corresponding to the strain sensor 138. Similar to the above-mentioned strain sensors 127 and 128, the strain sensors 138 and 139 are used to suppress the influence of noise such as temperature and vibration on the detected value of the thrust load by comparing the detected values ​​of the two and outputting the result of the comparison.

[0036] Here, elastically deformable body 108 for thrust load detection and reference body 109 for thrust load comparison are both arranged in an orientation such that their plate surfaces (planes perpendicular to the direction of elastic deformation) face the axial direction along axis 105x of external force receptor 105, and are arranged with the same material, shape and dimensions, and orientation in a direction along the plane perpendicular to axis 105x. As a result, elastically deformable body 108 for thrust load detection and reference body 109 for thrust load comparison are both arranged in an orientation suitable for primarily detecting the thrust load of external force receptor 105, and are arranged so as to have an equivalent positional relationship with respect to external force receptor 105 when viewed in the axial direction along the axis along which the thrust load is detected. Therefore, elastically deformable body 108 for thrust load detection and reference body 109 for thrust load comparison are configured to be equally affected by noise elements, such as axial vibrations along the axis, among the influences received from external force receptor 105 when detecting a thrust load. Therefore, by outputting the comparison results such as the difference or ratio between the detection values ​​of the deformation detector 138 for detecting thrust loads and the deformation detector 139 for comparing thrust loads, it is possible to further reduce the effects of temperature and noise on the detection values ​​of thrust loads.

[0037] As will be described later, the calibration of the torque detection values ​​by strain sensors 127, 128 in torque detection structure 100B described above can be performed by deriving the relationship between the torque value applied in the rotational direction to external force receptor 105 and the detection value according to this embodiment. In this case, in torque detection structure 100B, external force receptor 105 is configured as a hydrostatic bearing structure by radial support portion 106, and therefore, even for minute torque values, there is almost no friction involved and the detection value is not affected, so that the torque that workpiece T receives from tool S, i.e., the torque load that tool S receives, can be detected with high sensitivity and accuracy.

[0038] In particular, in torque detection structure 100B, displacement in the rotational direction around axis 105x of external force receptor 105 is transmitted to elastically deformable body 117 for torque detection by connecting member 111 and transmission member 112, which are external force transmission parts for torque detection, causing elastic deformation, but because the fixed part of elastically deformable body 117 is arranged above axis 105x and the displacement part of elastically deformable body 117 is arranged below axis 105x, the length of the area where elastic deformation occurs can be sufficiently ensured, thereby preventing the detection structure from becoming larger and improving detection sensitivity and detection accuracy. In this case, elastically deformable body 117 for torque detection has a displacement part (tip) on the opposite side from the fixed part as a free end, so detection sensitivity and detection accuracy can be further improved so that even extremely slight torque can be detected.

[0039] Furthermore, in torque detection structure 100B, when displacement in a predetermined rotation direction among the rotation directions of external force receptor 105 about axis 105x is transmitted to elastically deformable body 117 for torque detection and elastic deformation occurs, vibration in the rotation direction of external force receptor 105 also causes vibration in the amount of elastic deformation, which may adversely affect torque detection. This is all the more true because the displacement portion of elastically deformable body 117 is a free end. However, in this embodiment, holding member 113 is provided that applies a holding force to elastically deformable body 117 in a direction opposite to the direction of displacement of transmission member 112. This holding member 113 receives the elastic force of elastic member 114 and suppresses the elastic deformation of elastically deformable body 117 in the opposite direction, thereby absorbing vibration in the rotation direction of the displacement portion (tip portion) of elastically deformable body 117 and contributing to stable torque detection.

[0040] 13 shows how the elastically deformable body 117 for torque detection is attached to a jig 150 for calibrating detection values ​​and calibration work is performed. The jig 150 has a step 151 to which a fixing portion 117s of the elastically deformable body 117 for torque detection is attached, and a step-down surface 152 that is one step (approximately 10 mm) lower than the step 151. The elastically deformable body 117 is installed such that the fixing portion 117s is fixed onto the step 151 with a bolt or the like, and the portion of the elastically deformable body 117 other than the fixing portion 117s protrudes above the step-down surface 152. A load is then applied to a displacement portion 117t (corresponding to the tip 117a) of the elastically deformable body 117 by a tip 160p of a pressure pin 160 of a strength testing machine or the like, and the detection value of the strain sensor 127, which is a deformation detector for torque detection, when pressure is applied is measured while the load is changed. The relationship between the load applied by the pressure pin 160 and the detection value of the strain sensor 127 is identified by the least squares method or the like, and a correspondence relationship such as a coefficient or function for obtaining a calibrated value (load) from the detection value is determined based on this relationship. The correspondence relationship obtained by this calibration work is incorporated into the output section of the torque detection signal of the stress detection device 100 so that a calibrated torque value can be output.

[0041] Next, the calibration of the thrust load detection value by strain sensors 138, 139 in thrust load detection structure 100C can be performed by deriving the relationship between the value of the thrust load applied in the axial direction to external force receptor 105 and the above-mentioned detection value in this embodiment, as will be described later. In this case, in thrust load detection structure 100C, external force receptor 105 is configured as a hydrostatic bearing structure by thrust support portion 107, and therefore there is almost no friction even for minute thrust values, so that the detection value is not affected, and therefore the thrust load that workpiece T receives from tool S, i.e., the thrust load that tool S receives, can be detected with high sensitivity and accuracy.

[0042] In particular, in thrust load detection structure 100C, thrust support portion 107B, which is the external force transmission portion, transmits axial displacement along axis 105x of external force receptor 105 to elastically deforming body 108 for thrust load detection, causing elastic deformation. Elastically deforming body 108 has a pair of fixed portions, located above and below axis 105x of external force receptor 105, fixed to support frame 100A, and a displacement portion attached to thrust support portion 107B midway between the pair of fixed portions, is supported from both sides. This makes it possible to generate a balanced elastic deformation pattern of elastically deforming body 108, thereby improving detection sensitivity and detection accuracy while preventing the detection structure from becoming larger. At this time, since the elastically deformable body 108 for thrust load detection is configured in a rectangular frame shape, elastically deformable portions each having a pair of fixed portion and displacement portion are provided on both the left and right sides of the axis 105x (along the direction perpendicular to the direction connecting the pair of upper and lower fixed portions), and therefore, by outputting the results using the detection values ​​by the deformation detectors 138, 138 in the elastically deformable portions on both the left and right sides, it is possible to obtain stable detection values ​​that are balanced vertically and horizontally. Also, since the elastically deformable body 108 for thrust load detection is configured in a rectangular frame shape, it is possible to arrange at least a part of the torque detection structure so that it passes through an opening in the frame without contacting it, and therefore the torque detection structure and thrust load detection structure can be configured compactly as a whole.

[0043] 14 shows how the elastically deformable body 108 for detecting thrust loads is attached to a jig 170 for calibrating detection values ​​and calibration work is performed. The jig 170 has stepped portions 171, 171 on the left and right sides in the figure to which are attached left and right fixing portions 108s, 108s of the elastically deformable body 108 for detecting thrust loads, and has a stepped undersurface 172 between these stepped portions 171 that is one step (approximately 10 mm) lower than the stepped portions 171. The elastically deformable body 108 is installed such that the fixing portions 108s, 108s on both sides are fixed onto the stepped portions 171 with bolts or the like, and the portion of the elastically deformable body 108 other than the fixing portions 108s protrudes above the stepped undersurface 172. A support plate 181 (the thrust direction support portion 107B itself may be used) corresponding to the thrust direction support portion 107B is attached to the displacement portion 108t (corresponding to the middle portion between the left and right in the figure) of the elastically deformable body 108, and a load is applied to this support plate 181 using the tip portion 180p of a pressure pin 180 of a strength testing machine or the like. While changing this load, the detection value of the strain sensor 138, which is a deformation detector for detecting the thrust load when this load is applied, is measured. The relationship between the load applied by the pressure pin 180 and the detection value of the strain sensor 138 is identified using the least squares method or the like, and a correspondence relationship such as a coefficient or function for obtaining a calibrated value (load) from the detection value is determined based on this relationship. The correspondence relationship obtained by this calibration work is incorporated into the output portion of the thrust load detection signal of the stress detection device 100 so that a calibrated thrust load value can be output.

[0044] It should be noted that the stress detection device according to the present invention is not limited to the above-described illustrated example, and various modifications can be made without departing from the spirit and scope of the present invention. For example, in the above embodiment, an example is described in which the load on the tool S is grasped by detecting the torque and thrust load when machining a workpiece T attached to the machining table 104 using the tool S. However, the present invention is not limited to such machining processes, and can be used in various applications in which the torque and thrust load are detected by detecting the stress generated in each detection structure that receives an external force. [Explanation of symbols]

[0045] 100...Stress detection device, 100A...Support frame, 101...Support main plate portion, 102, 103...Support side plate portion, 104...Workpiece table (chuck, gripping structure), 105...External force receptor, 105x...Axis, 105a...Front end portion, 105b...Thrust plate portion, 105c...Rear end portion, 106...Radial support portion, 106a, 107a, 107b...Fluid introduction portion, 107...Thrust support portion, 107A...(Front) thrust support portion, 107B...(Rear) thrust support portion Holding portion, 100B...torque detection structure, 111...connecting member, 112...transmission member, 112a...tip portion, 113...holding member, 113a...tip portion, 114...elastic member (leaf spring), 115...support shaft, 117...elastically deformable body for torque detection, 118...reference body for torque comparison, 127, 128...strain sensor, 100C...thrust load detection structure, 108...elastically deformable body for thrust load detection, 109...reference body for thrust load comparison, 138, 139...strain sensor

Claims

1. an external force receptor that directly or indirectly receives an external force; a bearing portion that supports the external force receiver in a radial direction; a support frame that supports the external force receptor via the bearing portion; a torque detection structure for detecting torque in a rotational direction around an axis of the external force receptor; A stress detection device comprising: The torque detection structure includes: an elastically deformable body for torque detection, the elastically deformable body having a fixed portion attached to the support frame at a position on one side with respect to an axis of the external force receptor, extending from the fixed portion to the other side with respect to the axis, and including a displacement portion at a position on the other side, the region between the fixed portion and the displacement portion being configured to be elastically deformable in the rotation direction; a deformation detector for torque detection that detects an amount of elastic deformation in the region of the elastic deformation body for torque detection; an external force transmission unit for torque detection that is connected to the external force receptor in the rotational direction and that abuts against the displacement unit in the rotational direction; having A stress detection device characterized by:

2. The torque detection elastic deformation body is attached so that the fixed portion and the displacement portion are arranged vertically and extend vertically downward from the fixed portion. The stress detection device according to claim 1 .

3. the displacement portion of the torque detection elastic deformation body is a free end. The stress detection device according to claim 1 .

4. the torque detection structure further includes a holding member that holds the displacement portion in a direction opposite to a contact direction of the external force transmission portion for torque detection and that applies a holding force that prevents the displacement portion from being separated from the external force transmission portion for torque detection. A stress detection device according to any one of claims 1 to 3.

5. The torque detection structure further includes a reference body for torque comparison that is made of the same material, has the same shape and dimensions as the elastically deformable body for torque detection, and is installed in the same posture as the elastically deformable body for torque detection, and a deformation detector for torque comparison that detects an amount of elastic deformation in a region of the reference body for torque comparison that corresponds to the region of the elastically deformable body for torque detection. The stress detection device according to claim 1 .

6. the elastically deformable body for torque detection and the reference body for torque comparison are arranged along the axis; The stress detection device according to claim 5 .

7. the bearing portion has a thrust direction support portion that supports the external force receptor in a thrust direction, further comprising a thrust load detection structure that detects a thrust load in an axial direction along the axis of the external force receptor, The thrust load detection structure includes: an elastically deformable body for detecting a thrust load, the elastically deformable body having a pair of fixed parts attached to the support frame at positions on one side and the other side of the axis of the external force receptor, extending between the pair of fixed parts and including a displacement part located in the vicinity of the axis therebetween, the regions between the pair of fixed parts and the displacement part being configured to be elastically deformable in the axial direction; a deformation detector for detecting a thrust load that detects an amount of elastic deformation in the region of the elastic deformation body for detecting a thrust load; an external force transmission portion for detecting a thrust load, which faces the external force receptor in the axial direction via a support portion in the thrust direction and abuts against the displacement portion in the axial direction; having The stress detection device according to claim 1 .

8. The thrust load detection structure includes: a reference body for thrust load comparison, which is made of the same material as the elastically deformable body for thrust load detection, has the same shape and dimensions, and is installed in the same posture; a deformation detector for thrust load comparison that detects an amount of elastic deformation in a region of the reference body for thrust load comparison that corresponds to the region of the elastically deformable body for thrust load detection; further comprising The stress detection device according to claim 7.

9. the elastically deformable body for detecting the thrust load and the reference body for comparing the thrust load are arranged along a plane perpendicular to the axis; The stress detection device according to claim 8.

10. the elastically deformable body for detecting thrust load extends between the pair of fixed parts and includes two sets of elastically deformable parts with the displacement part therebetween, on both sides along a direction perpendicular to a direction connecting the pair of fixed parts with respect to the axis, A stress detection device according to any one of claims 7 to 9.

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