JP7767033B2 - Linear motion guide unit and method for measuring load of linear motion guide unit - Google Patents

Description

This disclosure relates to a linear guide unit and a method for measuring the load of a linear guide unit.

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

Patent Document 1 describes a method for detecting strain in 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 attached to both ends of the casing in the sliding direction. The casing consists of a mounting portion that is horizontal with the upper surface of the track rail, and a pair of sleeve portions that extend downward from both widthwise ends of the mounting portion and face each other across the track rail.

In Patent Document 1, two strain detection sensors are arranged adjacent to each other on the widthwise side of the casing. In this publication, each sensor detects strain occurring on the side of the casing, and the direction of the load acting on the casing is determined by calculating the strain ratio based on the detected strain value.

Japanese Patent Application Laid-Open No. 2007-263286

In Patent Document 1, errors in the strain ratio value may occur due to measurement errors in the strain value on the side of the casing and individual differences in parts (casings, sensors, etc.). For this reason, Patent Document 1 has the problem of making it difficult to accurately determine the direction of the load applied to the casing.

The purpose of this disclosure is to provide a linear guide unit and a load measurement method for a linear guide unit that can more accurately determine the direction of the load applied to the casing.

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 arranged 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 arranged on the casing, an end surface strain sensor arranged on the casing, and a pair of direction change members arranged at both longitudinal ends of the casing. The rail includes a pair of rail-side raceway surfaces arranged on both sides in a width direction perpendicular to the longitudinal direction and extending in the longitudinal direction. The casing includes a casing main body extending in the width direction and a pair of sleeve portions connected to both sides of the casing main body in the width direction. The pair of sleeve portions form 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 rollway paths between the pair of rail-side raceway surfaces. The casing is formed with a pair of return paths that extend along each of the pair of rail-side raceway surfaces and are through-holes that penetrate the casing. The pair of direction change members have a direction change path formed that connects the rolling element rolling path and the return path. The rolling elements circulate in a circular track formed by the rolling element rolling path, return path, and direction change path. The side strain sensor is located 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 sensor is located on the casing end surface, which is the end surface of the casing in the longitudinal direction.

The load measurement method for a linear motion guide unit according to the present disclosure is a method for measuring the load applied to the casing of 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 surface strain sensor.

This disclosure provides a linear guide unit and a method for measuring the load on a linear guide unit that can more accurately determine the direction of the load applied to the casing.

FIG. 1 is a perspective view showing the overall configuration of a linear motion guide unit according to an embodiment of the present invention. FIG. 2 is a front view showing an end face of a casing of the linear motion guide unit according to the embodiment. FIG. 3 is a block diagram showing the configuration of a strain detector for a linear motion guide unit according to an embodiment of the present invention. 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. 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.

[Overview 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.

Intensive research was conducted into ways 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.

The present disclosure is based on the above viewpoint. In other words, 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.

Furthermore, in the linear 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 strain sensors being placed adjacent to each other. This relaxes restrictions on the size of the strain sensors, making it easy to arrange multiple strain sensors even in a small casing.

In the linear motion guide unit described above, 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 on the opposite side of the rail-facing surface in the up-down direction perpendicular to the longitudinal and width directions. The end face strain sensor may be positioned on the end face closer to the upper surface than the opening. This configuration allows for more sensitive detection of strain occurring on the casing end face.

In the linear motion guide unit described above, 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 positioned in the width direction at a position on the end face closer to the side of the casing than the rail-side rolling surface, and closer to the rail-side rolling surface than the opening. This configuration allows for even more sensitive detection of strain occurring on the casing end face.

In the linear motion guide unit described above, 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 sensor may be positioned closer to the upper surface than the side surface strain sensor. This configuration allows for even more sensitive detection of strain occurring on the casing end surface.

In the linear motion guide unit described above, the sensor mounting area of the casing end face where the end face strain sensor is mounted may have a greater surface roughness than the area of the end face other than the sensor mounting area. This configuration makes it easy to mount the end face strain sensor on the casing end face.

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. This configuration allows the direction of the load applied to the casing to 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.

The 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.

In the load measurement method for the linear motion guide unit described above, 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. It may also be determined that a compressive load is being applied to the casing when the output of the end face strain sensor is a negative value. This method makes it possible to easily and accurately determine the direction of the load being applied to the casing.

[Specific Example of the 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.

First, the configuration of the linear guide unit 1 according to this embodiment will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing the overall configuration of the linear guide unit 1. Figure 2 is a front view of the linear 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. Figure 3 is a block diagram showing the configuration of the strain detection device 70 of the linear guide unit 1.

Referring to FIG. 1, the linear motion guide unit 1 mainly comprises a rail 10 and a slider 20. The rail 10 extends linearly in the longitudinal direction D1. The slider 20 is attached to the rail 10 so as to sandwich the rail 10 from both sides in the 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.

Referring to Figure 2, the rail 10 includes a rail upper surface 15, a rail lower surface 16 opposite the rail upper surface 15 in the up-down direction D3 (a direction perpendicular to the longitudinal direction D1 and the width direction D2), and a pair of rail rolling surfaces (a first rail rolling surface 11 and a second rail rolling surface 12) arranged on both sides in the width direction D2. The rail upper surface 15, the rail lower surface 16, the first rail rolling surface 11, and the second rail rolling surface 12 extend in the longitudinal direction D1 (a direction into the plane of the paper in Figure 2). Two first rail rolling surfaces 11 and two second rail rolling surfaces 12 are formed side by side in the up-down direction D3.

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

The casing body 24 includes a rail-facing 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-facing surface 36 in the vertical direction D3. 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 are formed on the pair of sleeve portions. 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.

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 (Figure 1) are respectively disposed on this casing end surface 37. The first sleeve portion 25 includes a first casing side surface 38, which is the surface opposite 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 the side facing the rail 10 in the width direction D2.

Referring to FIG. 2, the linear guide unit 1 is provided with a plurality of rolling elements (first rolling elements 41 and second rolling elements 42) arranged between the rail 10 and the casing 21 so as to be able to roll while in contact with the rail 10 and the casing 21. The first casing-side rolling 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 rolling surface 11, with the first rolling elements 41 arranged in this first rolling element transfer path. The first rolling elements 41 are in contact with the first rail-side rolling surface 11 and the first casing-side rolling surface 31. The second casing-side rolling 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 rolling surface 12, with the second rolling elements 42 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.

The casing 21 is formed with a pair of return paths (first return path 51 and second return path 52), which are through-holes that extend along each of 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, penetrating the first sleeve portion 25 in the longitudinal direction D1 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 vertical 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 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 vertical 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.

The first end cap 22 has 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 closest to the casing top surface 35 of the two first rolling element rolling paths is connected to the first return path 51 that is farthest from the casing top surface 35 of the two first return paths 51 by the first direction change path. Furthermore, the first rolling element rolling path that is farthest from the casing top surface 35 of the two first rolling element rolling paths is 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. Similar to the first end cap 22, the second end cap 23 also has a first direction change path. When the slider 20 (Figure 1) moves linearly along the longitudinal direction D1 of the rail 10, the first rolling element 41 (Figure 2) circulates in the annular track formed by the first rolling element rolling path, the first return path 51, and the first direction change path.

Although not shown, the first end cap 22 and the second end cap 23 are formed with a second direction change path connecting the second rolling element rolling path and the second return path 52 (Figure 2), similar to the first direction change path. Therefore, as the slider 20 moves linearly, the second rolling element 42 (Figure 2) circulates in a circular orbit formed by the second rolling element rolling path, the second return path 52, and the second direction change path.

The linear motion guide unit 1 is equipped with a side strain sensor 61 and an end strain sensor 62 arranged on the casing 21. As shown in FIG. 1, in this embodiment, two side strain sensors 61 are arranged side by side in the longitudinal direction D1 on the first casing side surface 38. Two side 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 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 strain sensors 61 are strain gauges and are attached to the first casing side surface 38 and the second casing side surface 39, respectively, for example, with an adhesive.

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. In other words, 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, for example, with an adhesive. Note that Figure 2 shows an end surface strain sensor 62 placed on one casing end surface 37, but two end surface strain sensors 62 are similarly placed on the other casing end surface 37.

One end surface strain sensor 62 (the end surface strain sensor 62 on the right side in FIG. 2) is positioned on the casing end face 37 in the width direction D2, closer to the first casing side surface 38 than the first rail side raceway surface 11, and closer to the first rail side raceway surface 11 than the opening of the first return path 51. That is, this one end surface strain sensor 62 is positioned closer to the first casing side surface 38 than the dashed line L2 in FIG. 2 and closer to the first rail side 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 positioned on the casing end face 37 in the width direction D2, closer to the second casing side surface 39 than the second rail side raceway surface 12, and closer to the second rail side raceway surface 12 than the opening of the second return path 52. That is, the other end surface strain sensor 62 is located closer to the second casing side surface 39 than the dashed line L4 in Figure 2 and closer to the second rail-side rolling surface 12 than the dashed line L5.

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 areas of the casing end face 37 other than the sensor mounting area. 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.

Referring to FIG. 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.

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 load direction determination unit 75 are communicatively connected to a display unit 80, such as a display, and the estimated load value and load direction are displayed on the display unit 80. Below, we will explain how to measure the load on the casing 21 using the strain detection device 70.

This section describes a method for measuring the load on a linear motion guide unit according to this embodiment. This method measures the load applied to the casing 21 of the linear motion guide unit 1 as follows:

First, the side 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.

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 determines the direction of the load applied to the casing 21 based on the output of the end strain sensor 62. First, we will explain how to determine the direction of the load applied to the casing 21.

Figure 4 shows the relationship between the magnitude of the load applied to the casing 21 (horizontal axis) and the strain on the casing end surface 37 (vertical axis). In Figure 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 Figure 4, the inventors discovered that when a tensile load is applied to the casing 21, the strain generated on the casing end surface 37 is a positive value, while when a compressive load is applied to the casing 21, the strain generated on the casing end surface 37 is a negative value.

The end surface strain determination unit 73 determines whether the strain on the casing end surface 37 detected by the end surface strain detection unit 71 is positive or negative. Based on this determination result, 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, it determines that a compressive load is acting on the casing 21.

Next, we will explain how to determine the magnitude of the load applied to the casing 21. Figure 5 shows the relationship between the magnitude of the load applied to the casing 21 (horizontal axis) and the strain on the side of the casing (vertical axis). In Figure 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).

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

Next, we will explain how to calculate the internal load on the casing 21. First, the detection value of the lateral strain sensor 61 is substituted as the vertical axis value for a line having a slope between the slopes of lines (1) and (2) in the graph of Figure 5 (the line showing the relationship between the load and lateral strain when a lateral load in the width direction D2 is applied to the casing 21). This allows us to obtain an estimate of the load applied to the casing 21.

Next, as shown in Figure 4, the theoretical value B1 of end surface strain in the case of a tensile load (straight line (1)) and the theoretical value B2 of end surface strain in the case of a compressive load (straight line (2)) are calculated based on the estimated value A of the load applied to the casing 21. 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.

The difference between the theoretical values of end surface strain in the case of a tensile load and a compressive load is B1 - B2. Here, the rate of change of the load ratio relative to a 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 first and second casing side rolling surfaces 31, 32 (Figure 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 B2 in the case of a compressive load 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 perfect compressive load (upper load ratio 0% and lower load ratio 100%). When the load ratios of the pair of upper and lower first and second casing side rolling surfaces 31, 32 (Figure 2) are each 50%, this corresponds to a case in which a lateral load in the width direction D2 is applied to the casing 21.

Next, we will explain how to estimate the load on the entire casing 21. As shown in Figure 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 strain sensor 62 is arranged in each of the first to fourth regions R1 to R4.

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 described above. The moment M due to 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.

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 applied to 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 applied to the casing 21 can be determined easily and accurately.

Here, we will explain other embodiments.

The position of the end surface strain sensor 62 on the casing end surface 37 is not limited to the position shown in Figure 2. For example, the end surface strain sensor 62 may be located closer to the rail undersurface 16 than the dashed line L1 in Figure 2, or closer to the casing side surface than the dashed lines L3 and L5 in Figure 2, or between the dashed lines L2 and L4 in Figure 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.

The embodiments disclosed herein should be considered illustrative in all respects and not restrictive. The scope of the present invention is indicated by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

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 surface 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 (7)

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. 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. 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. 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. 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 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. 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. 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.