Linear motion guide unit and method for measuring load of linear motion guide unit

Abstract

To provide a linear motion guide unit capable of further correctly determining a direction of a load applied to a casing.SOLUTION: A linear motion guide unit is equipped with a rail, a casing, a plurality of rolling bodies, a side face strain sensor, an end face strain sensor, and a pair of direction conversion members. The rail includes a pair of rail side rolling faces disposed on both sides in a width direction. The casing includes a casing body, and a pair of sleeve portions connected to both sides in the width direction of the casing body. The pair of sleeve portions is formed with a casing side rolling face forming a pair of rolling body rolling paths between the rail side rolling faces. The casing is formed with a pair of return paths penetrating the casing. The pair of conversions is formed with a direction conversion path connecting the rolling body rolling paths and the return paths. The side face strain sensor is disposed on the casing side face. The end face strain sensor is disposed on a casing end face that is an end surface of the casing in a longitudinal direction.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to a linear motion guide unit and a load measuring method for a linear motion guide unit. [Background technology]

[0002] With the current advancement of IoT (Internet of Things), there is a growing demand in the market for technology to monitor the loads actually applied to mechanical components such as bearings, linear motion guide units, etc. This type of technology is described, for example, in Patent Document 1.

[0003] Patent Document 1 describes a strain detection method for a linear motion guide unit. This linear motion guide unit includes a track rail and a slider that slides along the track rail. The slider includes a casing and end caps provided on both ends of the casing in the sliding direction. The casing consists of a mounting part that is horizontal with the upper surface of the track rail and a pair of sleeve parts that extend downward from both ends of the mounting part in the width direction and face each other across the track rail.

[0004] In Patent Document 1, two strain detection sensors are arranged adjacent to each other on the side surface of the casing in the width direction. In this publication, the strain occurring on the side surface of the casing is detected by each sensor, and the direction of the load acting on the casing is determined by calculating the strain ratio based on the detected strain value. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2007-263286 Summary of the Invention [Problem to be solved by the invention]

[0006] In Patent Document 1, errors may occur in the value of the strain ratio due to measurement errors in the strain value on the side surface of the casing and individual differences in parts (casing, sensor, etc.). For this reason, Patent Document 1 has a problem in that it is difficult to accurately determine the direction of the load applied to the casing.

[0007] An object of the present disclosure is to provide a linear motion guide unit and a load measuring method for a linear motion guide unit that can more accurately determine the direction of a load applied to a casing. [Means for solving the problem]

[0008] A linear motion guide unit according to the present disclosure includes a rail, a casing movable along the longitudinal direction of the rail, a plurality of rolling elements disposed between the rail and the casing so as to be able to roll while in contact with the rail and the casing, a side strain sensor disposed on the casing, an end surface strain sensor disposed on the casing, and a pair of direction change members disposed at both ends of the casing in the longitudinal direction. The rail includes a pair of rail-side raceway surfaces disposed on both sides in a width direction perpendicular to the longitudinal direction and extending in the longitudinal direction. The casing includes a casing body extending in the width direction and a pair of sleeve portions connected to both sides of the casing body in the width direction. The pair of sleeve portions are formed with casing-side raceway surfaces that face the pair of rail-side raceway surfaces and extend in the longitudinal direction, forming a pair of rolling-element rolling paths between the pair of sleeve portions and the rail-side raceway surfaces. The casing is formed with a pair of return paths that are through-holes that extend along the pair of rail-side raceway surfaces and penetrate the casing. The pair of direction change members are formed with direction change paths that connect the rolling-element rolling paths and the return paths. The rolling elements circulate in a circular track formed by the rolling element rolling path, return path, and direction change path. The side strain sensors are arranged on the side of the casing, which is the surface opposite the side facing the rail of the sleeve portion in the width direction. The end surface strain sensors are arranged on the end surfaces of the casing, which are the end surfaces of the casing in the longitudinal direction.

[0009] A load measurement method for a linear motion guide unit according to the present disclosure is a method for measuring a load applied to a casing in the linear motion guide unit. In this method, the magnitude of the load applied to the casing is determined based on the output of a side strain sensor, and the direction of the load applied to the casing is determined based on the output of an end face strain sensor. [Effects of the Invention]

[0010] According to the present disclosure, it is possible to provide a linear motion guide unit and a method for measuring a load on a linear motion guide unit that can more accurately determine the direction of a load applied to a casing. [Brief explanation of the drawings]

[0011] [Figure 1] FIG. 1 is a perspective view showing the overall configuration of a linear motion guide unit according to an embodiment. [Figure 2] FIG. 2 is a front view showing an end face of a casing of the linear motion guide unit according to the embodiment. [Figure 3] FIG. 3 is a block diagram showing the configuration of a strain detector for a linear motion guide unit according to the embodiment. [Figure 4] FIG. 4 is a graph showing the relationship between the load applied to the casing and the strain on the end face of the casing. [Figure 5] FIG. 5 is a graph showing the relationship between the load applied to the casing and the strain on the side surface of the casing. DETAILED DESCRIPTION OF THE INVENTION

[0012] [Outline of the embodiment] A linear motion guide unit according to the present disclosure includes a rail, a casing movable along the longitudinal direction of the rail, a plurality of rolling elements disposed between the rail and the casing so as to be able to roll while in contact with the rail and the casing, a side strain sensor disposed on the casing, an end surface strain sensor disposed on the casing, and a pair of direction change members disposed at both ends of the casing in the longitudinal direction. The rail includes a pair of rail-side raceway surfaces disposed on both sides in a width direction perpendicular to the longitudinal direction and extending in the longitudinal direction. The casing includes a casing body extending in the width direction and a pair of sleeve portions connected to both sides of the casing body in the width direction. The pair of sleeve portions are formed with casing-side raceway surfaces that face the pair of rail-side raceway surfaces and extend in the longitudinal direction, forming a pair of rolling-element rolling paths between the pair of sleeve portions and the rail-side raceway surfaces. The casing is formed with a pair of return paths that are through-holes that extend along the pair of rail-side raceway surfaces and penetrate the casing. The pair of direction change members are formed with direction change paths that connect the rolling-element rolling paths and the return paths. The rolling elements circulate in a circular track formed by the rolling element rolling path, return path, and direction change path. The side strain sensors are arranged on the side of the casing, which is the surface opposite the side facing the rail of the sleeve portion in the width direction. The end surface strain sensors are arranged on the end surfaces of the casing, which are the end surfaces of the casing in the longitudinal direction.

[0013] An intensive study was carried out to find a way to accurately determine the direction of the load applied to the casing of a linear motion guide unit. As a result, it was discovered that, at the end face of the casing, when a compressive load (downward load) is applied to the casing in the vertical direction, the strain value becomes negative, whereas when a tensile load (upward load) is applied to the casing in the vertical direction, the strain value becomes positive.

[0014] The present disclosure is based on the above viewpoint. That is, in a linear motion guide unit according to the present disclosure, a strain sensor (end surface strain sensor) is disposed on the end surface of the casing, and based on the positive or negative detected value of the end surface strain sensor, it is possible to determine whether the load applied in the vertical direction to the casing is a compressive load or a tensile load. Therefore, the linear motion guide unit of the present disclosure makes it possible to more accurately determine the direction of the load applied to the casing.

[0015] Furthermore, in the linear motion guide unit according to the present disclosure, in addition to the end face strain sensors, strain sensors are also arranged on the side surfaces of the casing (side surface strain sensors). This makes it possible to avoid having strain sensors adjacent to each other. This relaxes the size restrictions on the strain sensors, making it easy to arrange multiple strain sensors even in a small casing.

[0016] In the linear motion guide unit, an opening may be formed in the end face of the casing, which is the end of the return path. The casing body may include a rail-facing surface that faces the rail, and an upper surface located opposite the rail-facing surface in the up-down direction perpendicular to the longitudinal and width directions. The end face strain sensor may be located in a position on the end face closer to the upper surface than the opening. This configuration allows for more sensitive detection of strain occurring in the casing end face.

[0017] In the linear motion guide unit, an opening may be formed in the end face of the casing, which is the end of the return path. The end face strain sensor may be disposed in a position on the end face in the width direction that is closer to the side surface of the casing than the rail-side rolling surface and closer to the rail-side rolling surface than the opening. This configuration makes it possible to detect strain occurring in the casing end face with even higher sensitivity.

[0018] In the linear motion guide unit, the casing body may include a rail-facing surface that faces the rail and an upper surface located on the opposite side of the rail-facing surface in the up-down direction perpendicular to the longitudinal and width directions. The end surface strain sensors may be located closer to the upper surface than the side surface strain sensors. This configuration allows for even more sensitive detection of strain occurring on the casing end surfaces.

[0019] In the linear motion guide unit, the sensor mounting area of ​​the end face of the casing where the end face strain sensor is mounted may have a surface roughness greater than that of the area of ​​the end face other than the sensor mounting area. With this configuration, the end face strain sensor can be easily mounted on the casing end face.

[0020] The linear motion guide unit may further include an end surface strain detection unit that detects the output of the end surface strain sensor, an end surface strain determination unit that determines whether the output of the end surface strain sensor is positive or negative, and a load direction determination unit that determines the direction of the load applied to the casing based on the determination result of the end surface strain determination unit. With this configuration, the direction of the load applied to the casing can be automatically and accurately determined. Note that the end surface strain detection unit, end surface strain determination unit, and load direction determination unit may be configured as a single unit in part or in whole.

[0021] A load measurement method for a linear motion guide unit according to the present disclosure is a method for measuring the load applied to a casing in the linear motion guide unit. This method determines the magnitude of the load applied to the casing based on the output of the side strain sensor, and determines the direction of the load applied to the casing based on the output of the end face strain sensor. This method makes it possible to more accurately determine the direction of the load applied to the casing based on the strain value of the casing end face.

[0022] In the load measurement method for the linear motion guide unit, it may be determined that a tensile load is being applied to the casing when the output of the end face strain sensor is a positive value, or that a compressive load is being applied to the casing when the output of the end face strain sensor is a negative value. With this method, the direction of the load being applied to the casing can be determined simply and accurately.

[0023] [Specific example of embodiment] Next, an example of a specific embodiment of the linear guide unit and the load measuring method for the linear guide unit of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are given the same reference characters, and their description will not be repeated.

[0024] First, the configuration of a linear motion guide unit 1 according to this embodiment will be described with reference to Figs. 1 to 3. Fig. 1 is a perspective view showing the overall configuration of the linear motion guide unit 1. Fig. 2 is a front view of the linear motion guide unit 1 as seen from the longitudinal direction D1 of the rail 10, with the first end cap 22 removed from the casing 21. Fig. 3 is a block diagram showing the configuration of a strain detector 70 of the linear motion guide unit 1.

[0025] Referring to FIG. 1, the linear motion guide unit 1 mainly includes a rail 10 and a slider 20. The rail 10 extends linearly in a longitudinal direction D1. The slider 20 is attached to the rail 10 so as to sandwich the rail 10 from both sides in a width direction D2 (a direction perpendicular to the longitudinal direction D1), and is movable along the longitudinal direction D1. The slider 20 includes a casing 21, and a first end cap 22 and a second end cap 23 (a pair of direction change members). As shown in FIG. 1, the first end cap 22 and the second end cap 23 are disposed at both ends of the casing 21 in the longitudinal direction D1.

[0026] Referring to Figure 2, rail 10 includes a rail upper surface 15, a rail lower surface 16 opposite to rail upper surface 15 in the up-down direction D3 (a direction perpendicular to longitudinal direction D1 and width direction D2), and a pair of rail raceways (first rail raceway surface 11 and second rail raceway surface 12) located on both sides in width direction D2. Rail upper surface 15, rail lower surface 16, first rail raceway surface 11, and second rail raceway surface 12 extend in longitudinal direction D1 (a direction into the depth of the paper in Figure 2). Two first rail raceways 11 and two second rail raceways 12 are formed side by side in the up-down direction D3.

[0027] The casing 21 includes a casing body 24 and a pair of sleeve portions (a first sleeve portion 25 and a second sleeve portion 26). As shown in FIG. 2, the casing body 24 extends in a width direction D2 when viewed from a longitudinal direction D1. The casing body 24 includes a first end portion 24A located outside the rail 10 in the width direction D2, and a second end portion 24B located outside the rail 10 in the width direction D2 and opposite the first end portion 24A. The pair of sleeve portions are connected to both sides of the casing body 24 in the width direction D2. The first sleeve portion 25 extends in the vertical direction D3 from the first end portion 24A of the casing body 24 toward the rail lower surface 16. The second sleeve portion 26 extends in the vertical direction D3 from the second end portion 24B of the casing body 24 toward the rail lower surface 16.

[0028] The casing body 24 includes a rail-opposing surface 36 that faces the rail upper surface 15, and a casing upper surface 35 (upper surface) located on the opposite side of the rail-opposing surface 36 in the vertical direction D3. The pair of sleeve portions are formed with a pair of casing-side raceway surfaces (first casing-side raceway surface 31 and second casing-side raceway surface 32) that face the pair of rail-side raceway surfaces. The first casing-side raceway surface 31 is parallel to the first rail-side raceway surface 11 and extends in the longitudinal direction D1. The second casing-side raceway surface 32 is parallel to the second rail-side raceway surface 12 and extends in the longitudinal direction D1. As shown in FIG. 2, the first casing-side raceway surface 31 and the second casing-side raceway surface 32 are formed in pairs, aligned in the vertical direction D3.

[0029] The casing 21 includes a casing end surface 37, which is the end surface of the casing 21 in the longitudinal direction D1. The first end cap 22 and the second end cap 23 (FIG. 1) are respectively arranged on this casing end surface 37. The first sleeve portion 25 includes a first casing side surface 38, which is the surface opposite to the side facing the rail 10 in the width direction D2. The second sleeve portion 26 includes a second casing side surface 39, which is the surface opposite to the side facing the rail 10 in the width direction D2.

[0030] 2, the linear motion guide unit 1 is provided with a plurality of rolling elements (first rolling elements 41 and second rolling elements 42) that are arranged between the rail 10 and the casing 21 and are capable of rolling while contacting the rail 10 and the casing 21. The first casing side raceway surface 31 forms a first rolling element transfer path (one of a pair of rolling element transfer paths) between itself and the first rail side raceway surface 11, and the first rolling elements 41 are arranged in this first rolling element transfer path. The first rolling elements 41 are in contact with the first rail side raceway surface 11 and the first casing side raceway surface 31. The second casing side raceway surface 32 forms a second rolling element transfer path (the other of the pair of rolling element transfer paths) between itself and the second rail side raceway surface 12, and the second rolling elements 42 are arranged in this second rolling element transfer path. The second rolling elements 42 are in contact with the second rail-side rolling surface 12 and the second casing-side rolling surface 32. The first rolling elements 41 and the second rolling elements 42 are, for example, cylindrical rollers, but are not limited to this.

[0031] The casing 21 is formed with a pair of return paths (a first return path 51 and a second return path 52), which are through holes that extend along the pair of rail-side rolling surfaces and penetrate the casing 21 in the longitudinal direction D1. As shown in FIG. 2 , the first return path 51 is a circular through hole when viewed from the longitudinal direction D1, and penetrates the first sleeve portion 25 in the longitudinal direction D1 so as to reach from one casing end face 37 to the other casing end face 37. Two first return paths 51 are formed in the first sleeve portion 25, side by side in the up-down direction D3. Like the first return path 51, the second return path 52 is also a circular through hole when viewed from the longitudinal direction D1. The second return path 52 penetrates the second sleeve portion 26 in the longitudinal direction D1 so as to reach from one casing end face 37 to the other casing end face 37. Two second return paths 52 are formed in the second sleeve portion 26, side by side in the up-down direction D3. An opening is formed on the end face of the first sleeve portion 25 in the longitudinal direction D1, which is the end face of the first return path 51 in the longitudinal direction D1, and an opening is formed on the end face of the second sleeve portion 26 in the longitudinal direction D1, which is the end face of the second return path 52 in the longitudinal direction D1.

[0032] The first end cap 22 is formed with a first direction change path that connects the first rolling element rolling path (the space between the first rail-side rolling surface 11 and the first casing-side rolling surface 31) and the first return path 51. More specifically, the first rolling element rolling path that is closer to the casing top surface 35 of the two first rolling element rolling paths is connected to the first return path 51 that is farther from the casing top surface 35 of the two first return paths 51 by the first direction change path. The first rolling element rolling path that is farther from the casing top surface 35 of the two first rolling element rolling paths is also connected to the first return path 51 that is closer to the casing top surface 35 of the two first return paths 51 by the first direction change path. Note that the second end cap 23 also has a first direction change path, similar to the first end cap 22. When the slider 20 (FIG. 1) moves linearly along the longitudinal direction D1 of the rail 10, the first rolling element 41 (FIG. 2) circulates in a circular track formed by the first rolling element rolling path, the first return path 51, and the first direction change path.

[0033] Although not shown, a second direction change path connecting the second rolling element rolling path and the second return path 52 (FIG. 2) is formed in the first end cap 22 and the second end cap 23 in the same manner as the first direction change path. Therefore, as the slider 20 moves linearly, the second rolling element 42 (FIG. 2) circulates in a circular track formed by the second rolling element rolling path, the second return path 52, and the second direction change path.

[0034] The linear motion guide unit 1 is equipped with a side surface strain sensor 61 and an end surface strain sensor 62 arranged in the casing 21. As shown in FIG. 1, in this embodiment, two side surface strain sensors 61 are arranged side by side in the longitudinal direction D1 on the first casing side surface 38. Two side surface strain sensors 61 are also arranged side by side in the longitudinal direction D1 on the second casing side surface 39 (FIG. 2). The side surface strain sensors 61 detect strain in the up-down direction D3 that occurs on the first casing side surface 38 and the second casing side surface 39. The side surface strain sensors 61 are strain gauges, and are attached to the first casing side surface 38 and the second casing side surface 39, respectively, by, for example, an adhesive.

[0035] Referring to FIG. 2, two end surface strain sensors 62 are arranged side by side in the width direction D2 on the casing end surface 37. More specifically, the end surface strain sensors 62 are arranged in a position on the casing end surface 37 closer to the casing top surface 35 in the up-down direction D3 than the openings of the first return path 51 and the second return path 52. That is, the end surface strain sensors 62 are located closer to the casing top surface 35 than the dashed line L1 in FIG. 2. Also as shown in FIG. 2, the end surface strain sensors 62 are arranged in a position closer to the casing top surface 35 than the side surface strain sensors 61. The end surface strain sensors 62 detect strain in the up-down direction D3 that occurs on the casing end surface 37. The end surface strain sensors 62 are strain gauges and are attached to the casing end surface 37 with, for example, an adhesive. Although FIG. 2 shows the end surface strain sensor 62 arranged on one casing end surface 37, two end surface strain sensors 62 are similarly arranged on the other casing end surface 37 as well.

[0036] One of the end surface strain sensors 62 (the end surface strain sensor 62 on the right side in FIG. 2) is disposed in the width direction D2 at a position on the casing end face 37 closer to the first casing side surface 38 than the first rail raceway surface 11 and closer to the first rail raceway surface 11 than the opening of the first return path 51. In other words, the one end surface strain sensor 62 is disposed closer to the first casing side surface 38 than the dashed line L2 in FIG. 2 and closer to the first rail raceway surface 11 than the dashed line L3. Similarly, the other end surface strain sensor 62 (the end surface strain sensor 62 on the left side in FIG. 2) is disposed in the width direction D2 at a position on the casing end face 37 closer to the second casing side surface 39 than the second rail raceway surface 12 and closer to the second rail raceway surface 12 than the opening of the second return path 52. That is, the other end face strain sensor 62 is located closer to the second casing side surface 39 than the dashed line L4 in FIG. 2 and closer to the second rail-side rolling surface 12 than the dashed line L5.

[0037] In this embodiment, the sensor mounting area of ​​the casing end face 37 where the end face strain sensor 62 is mounted has a greater surface roughness than the other areas of the casing end face 37. However, the linear motion guide unit of the present disclosure is not limited to this, and the surface roughness of the casing end face 37 may be uniform.

[0038] 3, the linear motion guide unit 1 further includes a strain detection device 70. As shown in FIG. 3, the strain detection device 70 includes an end surface strain detection unit 71, a side surface strain detection unit 72, an end surface strain determination unit 73, a load estimation unit 74, and a load direction determination unit 75.

[0039] The end surface strain detection unit 71 detects the output of the end surface strain sensor 62. The side surface strain detection unit 72 detects the output of the side surface strain sensor 61. The end surface strain detection unit 71 and the side surface strain detection unit 72 constitute a receiving unit that receives data from the end surface strain sensor 62 and the side surface strain sensor 61. The end surface strain determination unit 73 determines whether the output of the end surface strain sensor 62 is positive or negative. The load estimation unit 74 estimates the magnitude of the load applied to the casing 21 based on the output of the side surface strain sensor 61. The load direction determination unit 75 determines the direction of the load applied to the casing 21 based on the determination result of the end surface strain determination unit 73. The end surface strain determination unit 73, the load estimation unit 74, and the load direction determination unit 75 constitute a calculation unit. The load estimation unit 74 and the load direction determination unit 75 are communicably connected to a display unit 80 such as a display, and the estimated value of the load and the direction of the load are displayed on the display unit 80. Hereinafter, the load measurement of the casing 21 performed using the strain detection device 70 will be described.

[0040] A method for measuring the load of the linear motion guide unit according to this embodiment will now be described. In this method, the load applied to the casing 21 of the linear motion guide unit 1 is measured as follows.

[0041] First, the side surface strain sensor 61 detects the strain in the vertical direction D3 occurring on the first casing side surface 38 and the second casing side surface 39, and the end surface strain sensor 62 detects the strain in the vertical direction D3 occurring on the casing end surface 37. These detection data are sent to the side surface strain detection unit 72 and the end surface strain detection unit 71, respectively.

[0042] Next, the strain detection device 70 determines the magnitude of the load applied to the casing 21 based on the output of the side strain sensor 61, and also determines the direction of the load applied to the casing 21 based on the output of the end surface strain sensor 62. First, the determination of the direction of the load applied to the casing 21 will be described.

[0043] 4 shows the relationship between the magnitude of the load applied to the casing 21 (horizontal axis) and the strain (vertical axis) of the casing end surface 37. In FIG. 4, (1) is data when a tensile load (upward load) in the vertical direction D3 is applied to the casing 21, and (2) is data when a compressive load (downward load) in the vertical direction D3 is applied to the casing 21. As shown in FIG. 4, the inventors have found that when a tensile load is applied to the casing 21, the strain generated at the casing end surface 37 is a positive value, and conversely, when a compressive load is applied to the casing 21, the strain generated at the casing end surface 37 is a negative value.

[0044] The end surface strain determination unit 73 determines whether the strain of the casing end surface 37 detected by the end surface strain detection unit 71 is positive or negative. Based on the result of this determination, the load direction determination unit 75 determines the direction of the load acting on the casing 21. That is, when the output of the end surface strain sensor 62 is a positive value, the load direction determination unit 75 determines that a tensile load is acting on the casing 21, and when the output of the end surface strain sensor 62 is a negative value, the load direction determination unit 75 determines that a compressive load is acting on the casing 21.

[0045] Next, the determination of the magnitude of the load applied to the casing 21 will be described. Fig. 5 shows the relationship between the magnitude of the load applied to the casing 21 (horizontal axis) and the strain on the side surface of the casing (vertical axis). In Fig. 5, (1) shows data when a tensile load (upward load) in the vertical direction D3 is applied to the casing 21, and (2) shows data when a compressive load (downward load) in the vertical direction D3 is applied to the casing 21. This correlation data is acquired in advance and stored in a storage unit (memory).

[0046] The load estimation unit 74 calculates the magnitude of the load applied to the casing 21 (the horizontal axis value in FIG. 5) based on the strain detected by the side strain detection unit 72 and the correlation data in FIG. 5. The direction of the load applied to the casing 21 is determined by the method described above. When a tensile load is applied to the casing 21, the correlation data (1) in FIG. 5 is used, whereas when a compressive load is applied to the casing 21, the correlation data (2) in FIG. 5 is used. That is, by using the strain on the side of the casing as the vertical axis value in the correlation data (1) or (2) in FIG. 5, an estimated value of the load applied to the casing 21 can be obtained as the horizontal axis value.

[0047] Next, a method for calculating the internal load in the casing 21 will be described. First, the detection value of the lateral strain sensor 61 is substituted as the vertical axis value for a line (the line showing the relationship between the load and the lateral strain when a lateral load in the width direction D2 is applied to the casing 21) having a slope between the slopes of lines (1) and (2) in the graph of Fig. 5. This allows an estimated value of the load applied to the casing 21 to be obtained.

[0048] Next, as shown in Figure 4, based on the estimated value A of the load applied to the casing 21, the theoretical value B1 of the end surface strain in the case of a tensile load (the case of line (1)) and the theoretical value B2 of the end surface strain in the case of a compressive load (the case of line (2)) are calculated. In the case of a tensile load, the load ratio on the pair of upper and lower first and second casing-side rolling surfaces 31, 32 (Figure 2) is 100% on the upper side and 0% on the lower side. On the other hand, in the case of a compressive load, the load ratio is 0% on the upper side and 100% on the lower side.

[0049] The difference between the theoretical values ​​of end surface strain under tensile load and compressive load is B1-B2. Here, the rate of change of the load ratio relative to the change in end surface strain is calculated by 100 / (B1-B2). Using this rate of change, the load ratio of the actual load on the pair of upper and lower casing-side rolling surfaces 31 and 32 (Fig. 2) can be calculated as follows: That is, the difference between the measured value of end surface strain detected by the end surface strain sensor 62 and the theoretical value of end surface strain under compressive load, B2, is calculated, and this difference is multiplied by the rate of change. This calculates the deviation of the load ratio from the case of a complete compressive load (upper load ratio: 0% and lower load ratio: 100%). When the load ratios of the pair of upper and lower casing-side rolling surfaces 31 and 32 (Fig. 2) are 50% each, a lateral load in the width direction D2 is applied to the casing 21.

[0050] Next, we will explain how to estimate the load on the entire casing 21. As shown in Fig. 1, the casing 21 can be divided into four regions (first to fourth regions R1 to R4) with the center C1 in the longitudinal direction D1 and width direction D2 as the origin. In this embodiment, one set of side strain sensor 61 and end surface strain sensor 62 is arranged in each of the first to fourth regions R1 to R4.

[0051] In the first region R1, the force F applied to the pair of upper and lower casing side rolling surfaces is calculated by multiplying the estimated load value by the load ratio. The moment M due to the force F, with the center C1 as the origin, is calculated by taking the cross product of the vector of this force F and the vector pointing from the center C1 toward the casing side rolling surfaces. This moment M is similarly calculated for the pair of upper and lower casing side rolling surfaces in the second to fourth regions R2 to R4, and by adding these up, the total load applied to the casing 21 can be estimated.

[0052] As described above, with the linear motion guide unit 1 according to this embodiment, the end surface strain sensor 62 is disposed on the casing end surface 37, so it is possible to determine whether the load acting on the casing 21 is a compressive load or a tensile load based on the positive or negative detected value of the end surface strain sensor 62. Therefore, the direction of the load acting on the casing 21 can be determined simply and accurately.

[0053] Here, other embodiments will be described.

[0054] The position of the end surface strain sensor 62 on the casing end surface 37 is not limited to the position shown in Fig. 2. For example, the end surface strain sensor 62 may be located closer to the rail underside 16 than the dashed line L1 in Fig. 2, or closer to the casing side surface than the dashed lines L3 and L5 in Fig. 2, or between the dashed lines L2 and L4 in Fig. 2. Furthermore, the side surface strain sensor 61 may be located closer to the casing top surface 35 than the end surface strain sensor 62.

[0055] The embodiments disclosed herein are illustrative in all respects and should not be construed as limiting. The scope of the present invention is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims. [Explanation of symbols]

[0056] 1 Linear motion guide unit, 10 Rail, 11 First rail side rolling surface, 12 Second rail side rolling surface, 15 Rail upper surface, 16 Rail lower surface, 20 Slider, 21 Casing, 22 First end cap, 23 Second end cap, 24 Casing body, 24A First end, 24B Second end, 25 First sleeve portion, 26 Second sleeve portion, 31 First casing side rolling surface, 32 Second casing side rolling surface, 35 Casing upper surface (upper surface), 36 Rail opposing surface, 37 Casing end surface, 38 First casing side surface, 39 Second casing side surface, 41 First rolling element, 42 Second rolling element, 51 First return path, 52 Second return path, 61 Side strain sensor, 62 End surface strain sensor, 70 Strain detection device, 71 End surface strain detection unit, 72 Side strain detection unit, 73 end strain determination unit, 74 load estimation unit, 75 load direction determination unit, 80 display unit, D1 longitudinal direction, D2 width direction, D3 up / down direction

Claims

1. Rails and a casing movable along the longitudinal direction of the rail; a plurality of rolling elements disposed between the rail and the casing so as to be able to roll while contacting the rail and the casing; a side strain sensor disposed on the casing; an end surface strain sensor disposed in the casing; a pair of direction-changing members disposed at both ends of the casing in the longitudinal direction, the rail includes a pair of rail-side rolling surfaces that are arranged on both sides in a width direction perpendicular to the longitudinal direction and extend in the longitudinal direction, The casing comprises: a casing body extending in the width direction; a pair of sleeve portions connected to both sides of the casing body in the width direction, the pair of sleeve portions are formed with casing-side rolling surfaces that face the pair of rail-side rolling surfaces, extend in the longitudinal direction, and form a pair of rolling element rolling paths between the casing-side rolling surfaces and the rail-side rolling surfaces, a pair of return paths, which are through holes that extend along the pair of rail-side rolling surfaces and penetrate the casing, are formed in the casing; The pair of direction change members are formed with direction change paths that connect the rolling element rolling paths and the return paths, the rolling elements circulate in an annular track formed by the rolling element rolling path, the return path, and the direction change path; the side strain sensor is disposed on a casing side surface, which is a surface of the sleeve portion opposite to a side facing the rail in the width direction, the end surface strain sensor is disposed on a casing end surface that is an end surface of the casing in the longitudinal direction, An opening, which is an end of the return path, is formed in the end surface of the casing, the end surface strain sensor is disposed in the width direction at a position on the end surface closer to the casing side surface than the rail-side rolling surface and closer to the rail-side rolling surface than the opening. Linear guide unit.

2. An opening, which is an end of the return path, is formed in the end surface of the casing, The casing body includes: a rail-facing surface that faces the rail; an upper surface located on the opposite side to the rail-opposing surface in a vertical direction perpendicular to the longitudinal direction and the width direction, 2. The linear motion guide unit according to claim 1, wherein said end surface strain sensor is disposed at a position on said end surface closer to said upper surface than said opening.

3. The casing body includes: a rail-facing surface that faces the rail; an upper surface located on the opposite side to the rail-opposing surface in a vertical direction perpendicular to the longitudinal direction and the width direction, 3. The linear motion guide unit according to claim 1, wherein the end surface strain sensor is disposed at a position closer to the upper surface than the side surface strain sensor.

4. 4. The linear motion guide unit according to claim 1, wherein a sensor mounting area of ​​said end face where said end face strain sensor is mounted has a surface roughness greater than that of an area of ​​said end face other than said sensor mounting area.

5. A rail; a casing movable along the longitudinal direction of the rail; a plurality of rolling elements disposed between the rail and the casing so as to be able to roll while contacting the rail and the casing; a side strain sensor disposed on the casing; an end surface strain sensor disposed in the casing; a pair of direction-changing members disposed at both ends of the casing in the longitudinal direction, the rail includes a pair of rail-side rolling surfaces that are arranged on both sides in a width direction perpendicular to the longitudinal direction and extend in the longitudinal direction, The casing comprises: a casing body extending in the width direction; a pair of sleeve portions connected to both sides of the casing body in the width direction, the pair of sleeve portions are formed with casing-side rolling surfaces that face the pair of rail-side rolling surfaces, extend in the longitudinal direction, and form a pair of rolling element rolling paths between the casing-side rolling surfaces and the rail-side rolling surfaces, a pair of return paths, which are through holes that extend along the pair of rail-side rolling surfaces and penetrate the casing, are formed in the casing; The pair of direction change members are formed with direction change paths that connect the rolling element rolling paths and the return paths, the rolling elements circulate in an annular track formed by the rolling element rolling path, the return path, and the direction change path; the side strain sensor is disposed on a casing side surface, which is a surface of the sleeve portion opposite to a side facing the rail in the width direction, the end surface strain sensor is disposed on a casing end surface that is an end surface of the casing in the longitudinal direction, an end surface strain detection unit that detects the output of the end surface strain sensor; an end surface strain determination unit that determines whether the output of the end surface strain sensor is positive or negative; a load direction determining section that determines a direction of a load applied to the casing based on a determination result of the end face strain determining section.

6. A method for measuring a load applied to the casing in the linear motion guide unit according to any one of claims 1 to 5, comprising: A load measuring method for a linear motion guide unit, which determines the magnitude of the load applied to the casing based on the output of the side strain sensor, and determines the direction of the load applied to the casing based on the output of the end face strain sensor.

7. determining that a tensile load is being applied to the casing when the output of the end surface strain sensor is a positive value; 7. A load measuring method for a linear motion guide unit according to claim 6, wherein it is determined that a compressive load is being applied to said casing when the output of said end face strain sensor is a negative value.

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