Bearing mechanism

Abstract

[Problem] To provide a bearing mechanism comprising a rolling bearing and a sliding bearing, and capable of supplying sufficient lubricant to the sliding bearing. [Solution] A bearing mechanism 1 comprises: first track bases 4L, 4R; second track bases 5L, 5R that move relative to the first track bases 4L, 4R and are shorter than the first track bases 4L, 4R; rolling bearings 6L, 6R disposed between the first track bases 4L, 4R and the second track bases 5L, 5R; sliding bearings 7L, 7R disposed on both sides in the front-rear direction of the rolling bearings 6L, 6R between the first track bases 4L, 4R and the second track bases 5L, 5R; and lubricant supply parts 18L, 18R that supply a lubricant 13 to the slide bearings 7L, 7R in conjunction with the movement of the second track bases 5L, 5R due to the rolling bearings 6L, 6R.

Description

Bearing mechanism

[0001] The present invention relates to a bearing mechanism in which a first raceway rail and a second raceway rail move relative to each other via a rolling bearing and a sliding bearing.

[0002] Bearing mechanisms can be broadly divided into those equipped with rolling bearings that use the rolling motion of rolling elements such as balls or rollers, and those equipped with plain bearings that use sliding motion. Bearing mechanisms using rolling bearings are often used under light to medium loads due to their features such as high precision, low sliding resistance without stick-slip, easy oil management, and the ability to calculate lifespan. However, they can be unsuitable for ultra-high precision equipment, grinding, or heavy cutting due to characteristics such as deformation of the rolling elements, vibration caused by the rolling elements entering and leaving the bearings, and low rigidity. On the other hand, bearing mechanisms using plain bearings have advantages such as high rigidity and high damping, but also disadvantages such as the occurrence of stick-slip and the need for a large oil film, which results in significant wear.

[0003] Therefore, a bearing mechanism has been proposed that can compensate for the shortcomings of both rolling bearings and plain bearings by including both. For example, Patent Document 1 describes a linear bearing in which a linear ball bearing is accommodated in a housing, and a pair of plain bearings are accommodated with a linear ball bearing sandwiched between them at both ends of the housing. In this linear bearing, two linear ball bearings are arranged in series on the axis, and an annular oil groove is arranged between each linear ball bearing, surrounding the outer periphery of the shaft.

[0004] Japanese Patent Application Laid-Open No. 2000-352420

[0005] For a bearing mechanism equipped with both a rolling bearing and a plain bearing to operate smoothly, oil film formation in the plain bearing is extremely important. In the above-mentioned conventional technology, oil is supplied to the linear ball bearing and plain bearing from the oil groove via the shaft, which poses the problem of insufficient oil supply to the plain bearing.

[0006] An object of the present invention is to provide a bearing mechanism that includes a rolling bearing portion and a plain bearing portion and that is capable of supplying a sufficient amount of lubricant to the plain bearing portion.

[0007] In order to achieve the above object, the bearing mechanism of the present invention comprises a first track, a second track that moves relative to the first track and is shorter than the first track, a rolling bearing unit arranged between the first and second track, a plain bearing unit arranged between the first and second track in the axial direction of the rolling bearing unit, and a lubricant supply unit that supplies lubricant to the plain bearing unit in conjunction with movement of the second track by the rolling bearing unit, and also has a preload adjustment screw that allows preload control.

[0008] The bearing mechanism of the present invention includes a rolling bearing and a plain bearing disposed axially of the rolling bearing between the first and second rails. The mechanism also includes a preload-applying screw that allows for preload adjustment according to operating conditions. For example, during fast forward movement or under light load, the rolling bearing supports the relative movement between the first and second rails, achieving stick-slip-free operation. Furthermore, during rapid acceleration / deceleration, heavy loads, or loads accompanied by vibration, both the rolling bearing and plain bearing support the relative movement between the first and second rails, achieving billow-free operation. In this invention, lubricant is supplied to the plain bearing in conjunction with table movement by the rolling bearing. This allows sufficient lubricant to be supplied to the plain bearing, resulting in favorable oil film formation in the plain bearing. Therefore, a bearing mechanism equipped with both a rolling bearing and a plain bearing can operate smoothly.

[0009] According to the present invention, in a bearing mechanism having both a rolling bearing portion and a plain bearing portion, it is possible to supply a sufficient amount of lubricant to the plain bearing portion.

[0010] 1. A perspective view showing the overall configuration of a bearing mechanism according to an embodiment. 2. A top view of the bearing mechanism when the table is located at the stroke center. 3. A side view of the bearing mechanism when the table is located at the stroke center. 4. A top view of the bearing mechanism when the table is located at the front stroke end. 5. A side view of the bearing mechanism when the table is located at the front stroke end. 6. A top view of the bearing mechanism when the table is located at the rear stroke end. 7. A side view of the bearing mechanism when the table is located at the rear stroke end. 8. A front view of the bearing mechanism as seen from the stroke direction. 9. A cross-sectional view showing the cross-sectional structures of the first raceway, the second raceway, and the plain bearing, taken along the line IX-IX in FIG. 2. 10. A perspective view showing the overall configuration of a bearing mechanism according to a modified example in which a seal member is provided. 11. A cross-sectional view showing the cross-sectional structures of the second raceway, the plain bearing, and the seal member, taken along the line XI-XI in FIG. 10. 12. A diagram showing an example of a displacement prevention mechanism according to a modified example in which a retainer displacement prevention mechanism is provided. 13. A diagram showing an example of the structure of a packing according to a modified example in which a packing for preventing lubricant leakage is provided.

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] 1. Bearing Mechanism Configuration The configuration of a bearing mechanism 1 according to an embodiment will be described with reference to FIGS. 1 to 9. FIG. 1 is a perspective view illustrating the overall configuration of the bearing mechanism 1 according to an embodiment. FIGS. 2 and 3 are top and side views of the bearing mechanism 1 when the table is positioned at the center of the stroke. FIGS. 4 and 5 are top and side views of the bearing mechanism 1 when the table is positioned at the front stroke end. FIGS. 6 and 7 are top and side views of the bearing mechanism 1 when the table is positioned at the rear stroke end. FIG. 8 is a front view of the bearing mechanism 1 as viewed from the stroke direction. FIG. 9 is a cross-sectional view of the first and second raceways and plain bearings taken along the line IX-IX in FIG. 2. Note that FIG. 8 shows, with dashed lines, screws that maintain the position of the plain bearings and adjust the preload. Screws are not shown in FIGS. 2 to 7 and 9. In the following description, directions such as up, down, left, right, front, and back are used as appropriate, and these directions correspond to the directions of the arrows shown in the figures.

[0013] 1 to 9, the bearing mechanism 1 is a linear guide mechanism that moves a table 3 linearly relative to a base 2. The bearing mechanism 1 has the base 2, the table 3, first track rails 4L, 4R, second track rails 5L, 5R, rolling bearings 6L, 6R, plain bearings 7L, 7R, and lubricant supply units 18L, 18R.

[0014] The base 2 is a member that serves as a base for the bearing mechanism 1 and is also called a bed. As shown in FIG. 8 , the base 2 has a substantially rectangular flat plate portion 2a and a protruding portion 2b that protrudes upward from the flat plate portion 2a, and is formed so that its shape is convex when viewed from the front-to-rear direction. The base 2 has mounting reference surfaces 2d on both left and right sides of the protruding portion 2b and on the top surface of the flat plate portion 2a. As shown in FIGS. 1 , 2 , 4 , and 6 , the protruding portion 2b extends in the front-to-rear direction on the flat plate portion 2a. The flat plate portion 2a and the protruding portion 2b have approximately the same length in the front-to-rear direction. It is noted that the bearing mechanism 1 may not include the base 2, and the base 2 may be installed on a user's device to which the bearing mechanism 1 is attached.

[0015] The table 3 is a member that is moved linearly in the front-to-rear direction relative to the base 2 and is positioned relative to the base 2, and is also called a block or stage. As shown in Figures 1 and 8, the table 3 has a substantially rectangular flat plate portion 3a and two side wall portions 3b that protrude downward from both left and right ends of the flat plate portion 3a, and is formed so that its shape when viewed from the front-to-rear direction is concave. The table 3 has mounting reference surfaces 3c on the inside of the flat plate portion 3a and on the inside of the two side wall portions 3b, respectively. The flat plate portion 3a and each side wall portion 3b have substantially the same length in the front-to-rear direction.

[0016] The first track rails 4L, 4R are linear members that guide the table 3 and are also called guide rails. The first track rails 4L, 4R are fixed to the base 2 with a plurality of bolts (not shown) so as to abut against the mounting reference surfaces 2d on both the left and right sides of the protrusion 2b of the base 2 and the mounting reference surface 2d on the top surface of the flat plate portion 2a. The first track rail 4R is disposed to the right of the protrusion 2b of the base 2, and the first track rail 4L is disposed to the left of the protrusion 2b of the base 2. The length of the first track rails 4L, 4R in the front-to-rear direction is approximately the same as the length of the base 2 in the front-to-rear direction. The lengths of the first track rails 4L, 4R and the base 2 in the front-to-rear direction may also be equal. The first track rails 4L, 4R may also be integral with the base 2.

[0017] 1, 3, 5, 7 and 8, V-shaped guide grooves 8L, 8R are formed on the outer sides of each of the first track rails 4L, 4R in the left-right direction. The guide groove 8R has rolling surfaces 8R1, 8R2 that come into contact with the outer peripheral surfaces of the rolling elements 9. The guide groove 8L has rolling surfaces 8L1, 8L2 that come into contact with the outer peripheral surfaces of the rolling elements 9. Note that if the rolling elements 9 are, for example, spherical, the guide grooves 8L, 8R may be formed in an arc shape.

[0018] The second track rails 5L, 5R are linear members that guide the table 3. The second track rails 5L, 5R are fixed to the underside of the table 3 with multiple bolts (not shown) so as to abut against the inner mounting reference surfaces 3c of the flat plate portion 3a of the table 3 and the inner mounting reference surfaces 3c of the two sidewall portions 3b. The second track rails 5L, 5R may be formed integrally with the table 3. As shown in FIG. 8 , the second track rail 5R is disposed between the right sidewall portion 3b of the table 3 and the first track rail 4R, facing the first track rail 4R in the left-right direction with a small gap GP (see FIG. 9 ). The second track rail 5L is disposed between the left sidewall portion 3b of the table 3 and the first track rail 4L, facing the first track rail 4L in the left-right direction with a small gap GP. The lengths of the second track rails 5L, 5R and the table 3 in the front-to-rear direction are approximately the same. In other words, the length of the second rails 5L, 5R in the front-rear direction is shorter than the length of the first rails 4L, 4R in the front-rear direction.

[0019] As shown in Figure 8, V-shaped guide grooves 10L, 10R are formed on the inside in the left-right direction of each of the second track rails 5L, 5R. Guide groove 10R has rolling surfaces 10R1, 10R2 that come into contact with the outer peripheral surfaces of the rolling elements 9. Guide groove 10L has rolling surfaces 10L1, 10L2 that come into contact with the outer peripheral surfaces of the rolling elements 9. The first track rail 4R and the second track rail 5R are arranged so that guide groove 8R and guide groove 10R face each other in the left-right direction. Similarly, the first track rail 4L and the second track rail 5L are arranged so that guide groove 8L and guide groove 10L face each other in the left-right direction.

[0020] The rolling bearings 6L, 6R are bearings that utilize the rolling motion of rolling elements 9. As shown in FIGS. 1 to 7 , the rolling bearing 6L is disposed between the first raceway rail 4L and the second raceway rail 5L, and the rolling bearing 6R is disposed between the first raceway rail 4R and the second raceway rail 5R. The rolling bearing 6L has a retainer 12L and multiple rolling elements 9, and the rolling bearing 6R has a retainer 12R and multiple rolling elements 9. The retainers 12L, 12R are sheet-like members that hold the multiple rolling elements 9. The rolling elements 9 are cylindrical roller members that are rotatably held by the retainers 12L, 12R. The rolling elements 9 are made of, for example, metal, and the retainers 12L, 12R are made of, for example, resin. The retainers 12L, 12R may be made of an oil-retaining material or a fluorine-containing resin material. Furthermore, the retainers 12L and 12R may be made of a metal material such as stainless steel, aluminum alloy, brass, or brass.

[0021] As shown in FIG. 9 , the retainer 12R is disposed between the first rail 4R and the second rail 5R so as to be movable in the front-rear direction. The retainer 12L is disposed between the first rail 4L and the second rail 5L so as to be movable in the front-rear direction. The thickness TH (see FIG. 9 ) of the retainers 12L, 12R is slightly smaller than the aforementioned gap GP. This allows the retainers 12L, 12R to substantially close the gap GP, preventing leakage of the lubricant 13, while allowing smooth front-rear movement together with the second rails 5L, 5R relative to the first rails 4L, 4R. As shown in FIGS. 1 to 7 , the retainers 12L, 12R rotatably hold the multiple rolling elements 9 so that the rolling elements 9a and 9b, whose rotational axis directions are approximately 90 degrees apart from each other, are alternately arranged in the front-rear direction and so that adjacent rolling elements 9a, 9b do not come into contact with each other. 1 to 7, for example, the outer peripheral surface of the rolling element 9a of the rolling bearing unit 6L contacts the rolling surface 8L1 of the first rail 4L and the rolling surface 10L2 of the second rail 5L. Also, for example, the outer peripheral surface of the rolling element 9b of the rolling bearing unit 6L contacts the rolling surface 8L2 of the first rail 4L and the rolling surface 10L1 of the second rail 5L. Also, for example, the outer peripheral surface of the rolling element 9a of the rolling bearing unit 6R contacts the rolling surface 8R1 of the first rail 4R and the rolling surface 10R2 of the second rail 5R. Also, for example, the outer peripheral surface of the rolling element 9b of the rolling bearing unit 6R contacts the rolling surface 8R2 of the first rail 4R and the rolling surface 10R1 of the second rail 5R.

[0022] The plain bearings 7L, 7R are bearings that utilize sliding motion. As shown in FIGS. 1 to 7 , the plain bearing 7L is disposed between the first raceway rail 4L and the second raceway rail 5L, on both sides of the rolling bearing 6L in the front-to-rear direction (an example of the axial direction), and the plain bearing 7R is disposed between the first raceway rail 4R and the second raceway rail 5R, on both sides of the rolling bearing 6R in the front-to-rear direction (an example of the axial direction). The plain bearing 7L includes a plain bearing 7Lf disposed in front of the rolling bearing 6L and a plain bearing 7Lb disposed behind the rolling bearing 6L. In other words, the plain bearings 7Lf, 7Lb are disposed at both ends of the second raceway rail 5L in the front-to-rear direction. The plain bearing 7R includes a plain bearing 7Rf disposed in front of the rolling bearing 6R and a plain bearing 7Rb disposed behind the rolling bearing 6R. That is, the plain bearings 7Rf, 7Rb are disposed at both ends of the second track rail 5R in the front-to-rear direction. The plain bearings 7L, 7R are fixedly held on the second track rails 5L, 5R and slide against the guide grooves 8L, 8R of the first track rails 4L, 4R as the table 3 moves. As shown in FIGS. 8 and 9 , the plain bearings 7L, 7R are generally rectangular prism-shaped components that fit into the V-shaped guide grooves 8L, 8R and the V-shaped guide grooves 10L, 10R, respectively. A lubricant supply groove 11 (see FIG. 9 ) is formed on the sliding surfaces of the plain bearings 7L, 7R that come into contact with the guide grooves 8L, 8R of the first track rails 4L, 4R. The plain bearings 7L, 7R may be made of a material such as a fluorine-containing resin material such as PTFE, an oil-impregnated material such as an oil-impregnated metal, a coating material, a composite material, or a ceramic material. The length L1 (see FIGS. 2 and 3) of the plain bearing portions 7L, 7R in the front-rear direction may be set based on, for example, the maximum value of the load acting on the bearing mechanism 1.

[0023] As shown in Figures 2 and 3, the length L2 of the retainer 12L in the front-rear direction is shorter than the length L3 obtained by subtracting the length L1 x 2 of the two plain bearings 7Lf and 7Lb from the length of the second track rail 5L in the front-rear direction. Similarly, the length L2 of the retainer 12R in the front-rear direction is shorter than the length L3 obtained by subtracting the length L1 x 2 of the two plain bearings 7Rf and 7Rb from the length of the second track rail 5R in the front-rear direction. Specifically, as shown in Figures 2 and 3, when the table 3 is positioned at the stroke center, the stroke length L4 over which the table 3 can move forward is approximately twice the length L5 between the front ends of the retainers 12L and 12R and the rear ends of the plain bearings 7Lf and 7Rf. Similarly, the stroke length L6 over which the table 3 can move rearward is approximately twice the length L7 between the rear ends of the retainers 12L and 12R and the front ends of the plain bearings 7Lb and 7Rb.

[0024] The lubricant supply units 18L, 18R supply lubricant 13 to the plain bearings 7L, 7R in conjunction with the movement of the table 3 by the rolling bearings 6L, 6R. The lubricant 13 is, for example, lubricating oil or grease, and is contained in lubricant reservoirs 14L, 14R. As shown in Figures 2 and 3 , the lubricant reservoir 14L is a space surrounded by the guide groove 8L of the first rail 4L, the guide groove 10L of the second rail 5L, the rear end of the plain bearing 7Lf, and the front end of the plain bearing 7Lb. The lubricant reservoir 14R is a space surrounded by the guide groove 8R of the first rail 4R, the guide groove 10R of the second rail 5R, the rear end of the plain bearing 7Rf, and the front end of the plain bearing 7Rb. 1 to 7, the lubricant reservoirs 14L, 14R are shown with dotted hatching to clearly identify their areas. The lubricant reservoirs 14L, 14R are filled with lubricant 13 supplied from a lubricant supply port (not shown) provided in the table 3. As shown in FIG. 9, a gap GP exists between the guide groove 8R of the first rail 4R and the guide groove 10R of the second rail 5R. However, this gap is very small (e.g., approximately 0.7 mm), and the retainer 12R is sandwiched in the gap, preventing leakage of the lubricant 13 from the lubricant reservoir 14R. The same applies to the lubricant reservoir 14L.

[0025] The lubricant supply units 18L, 18R supply lubricant 13 to the plain bearings 7L, 7R located on the movement side of the table 3 in response to the movement of the table 3 by the rolling bearings 6L, 6R. Specifically, when the table 3 moves from a state in which it is positioned at the center of its stroke as shown in Figures 2 and 3 to a state in which it moves to the front stroke end as shown in Figures 4 and 5, the rolling bearings 6L, 6R, including the retainers 12L, 12R and rolling elements 9, move forward by half the amount of movement of the table 3, so that the front ends of the retainers 12L, 12R and the rear ends of the plain bearings 7Lf, 7Rf are approximately aligned. As a result, the rolling elements 9, which move forward inside the guide grooves 8L, 10L and 8R, 10R in response to the forward movement of the table 3, pressure-feed the lubricant 13 contained in the lubricant reservoirs 14L, 14R to the plain bearings 7Lf, 7Rf located on the front side, that is, in the movement direction of the table 3. The lubricant 13 pumped to the plain bearing 7Lf is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Lf and the guide groove 8L, and the lubricant 13 pumped to the plain bearing 7Rf is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Rf and the guide groove 8R. Of the pumped lubricant 13, any excess lubricant 13 other than the lubricant 13 supplied to the plain bearings 7Lf, 7Rf moves through the minute gaps between the guide grooves 8L, 10L and the rolling elements 9 and the minute gaps between the guide grooves 8R, 10R and the rolling elements 9 to the space behind the rolling bearings 6L, 6R in the lubricant reservoirs 14L, 14R.

[0026] 2 and 3 to the rear stroke end as shown in Figures 6 and 7, the rolling bearings 6L, 6R including the retainers 12L, 12R and the rolling elements 9 move rearward by half the amount of movement of the table 3, so that the rear ends of the retainers 12L, 12R and the front ends of the plain bearings 7Lb, 7Rb are aligned. As a result, the rolling elements 9, which move rearward inside the guide grooves 8L, 10L and 8R, 10R in conjunction with the rearward movement of the table 3, pressure-feed the lubricant 13 contained inside the lubricant reservoirs 14L, 14R to the plain bearings 7Lb, 7Rb located on the rear side, in the direction of movement of the table 3. The lubricant 13 pumped to the plain bearing 7Lb is supplied to the sliding surface between the plain bearing 7Lb and the guide groove 8L, and the lubricant 13 pumped to the plain bearing 7Rb is supplied to the sliding surface between the plain bearing 7Rb and the guide groove 8R. Of the pumped lubricant 13, any surplus lubricant 13 other than the lubricant 13 supplied to the plain bearings 7Lb, 7Rb moves through the minute gaps between the guide grooves 8L, 10L and the rolling elements 9 and the minute gaps between the guide grooves 8R, 10R and the rolling elements 9 to the space in front of the rolling bearings 6L, 6R in the lubricant reservoirs 14L, 14R.

[0027] As described above, excess lubricant 13 inside the rolling bearings 6L, 6R is likely to leak out of the rolling bearings 6L, 6R as the bearing mechanism 1 slides. The lubricant 13 in the lubricant supply parts 18L, 18R is then pressure-fed to the plain bearings 7L, 7R provided at the ends by the movement of the retainers 12L, 12R, forming an oil film. As mentioned above, the lubricant supply groove 11 is formed on the sliding surfaces of the plain bearings 7L, 7R where they abut against the guide grooves 8L, 8R of the first raceways 4L, 4R.

[0028] As shown in FIGS. 1 and 8 , the table 3 is provided with multiple (e.g., three) preload adjustment screws 15 and multiple (e.g., six) set screws 16. The preload adjustment screws 15 are provided at three locations, front and rear, corresponding to the second track rail 5L on the side wall 3b on one side (the left side in this example) of the table 3. As shown in FIG. 8 , the tip of each preload adjustment screw 15 abuts the end face of the second track rail 5L opposite the first track rail 4L. When turned clockwise or counterclockwise, the second track rail 5L advances or retreats relative to the first track rail 4L, thereby adjusting the preload of each of the plain bearings 7Lf, 7Lb, 7Rf, and 7Rb. Note that, to avoid complication, the set screws 21, which are provided at approximately the same height as the preload adjustment screws 15, are not shown in FIG. 8 .

[0029] The fixing screws 16 are provided at a total of six locations: three locations at the front and rear of the flat plate portion 3a of the table 3 corresponding to the second track rail 5L, and three locations at the front and rear of the flat plate portion 3a of the table 3 corresponding to the second track rail 5R. When the fixing screws 16 are turned in the tightening direction, the second track rails 5L, 5R, whose positions (pressure) have been adjusted by the preload adjustment screws 15, are fixed to the table 3. The number of preload adjustment screws 15 and the number of fixing screws 16 are not limited to those described above. For example, the number of preload adjustment screws 15 may be a plurality other than one or three, and one, two, or four or more fixing screws 16 may be provided for each of the second track rails 5L, 5R.

[0030] 1 and 9, the second track rails 5L, 5R are provided with a plurality of (e.g., eight) fixing screws 21. The fixing screws 21 are provided at a total of eight locations: four front and rear locations corresponding to the plain bearings 7Lf, 7Lb on the back surface of the second track rail 5L opposite the first track rail 4L, and four front and rear locations corresponding to the plain bearings 7Rf, 7Rb on the back surface of the second track rail 5R opposite the first track rail 4R. The fixing screws 21 secure the plain bearings 7Lf, 7Lb to the second track rail 5L, and also secure the plain bearings 7Rf, 7Rb to the second track rail 5R, so that the plain bearings 7Lf, 7Lb and 7Rf, 7Rb do not shift in the front-to-rear direction, which is the direction of movement. 9, the fixing screws 21 are inserted from the back surface of the second rail 5R until their tips reach the first rail 4R side of the left-right center of the plain bearing 7Rf, fixing the second rail 5R and the plain bearing 7Rf. The same applies to the other fixing screws 21. The number of fixing screws 21 is not limited to eight. For example, one fixing screw 21 may be provided for each of the plain bearings 7Lf, 7Lb, 7Rf, and 7Rb, or three or more fixing screws may be provided for each.

[0031] As shown in Figure 9, the retainer 12R is sandwiched between the first and second rails 4R and 5R. If the gap GP between the first and second rails 4R and 5R is, for example, 0.7 mm and the thickness TH of the retainer 12R is, for example, 0.5 mm, then minute gaps of approximately 0.1 mm are formed between the retainer 12R and the first and second rails 4R and 5R on both the left and right sides. This allows the retainer 12R to move in the front-to-rear direction with little sliding resistance. The same is true for the retainer 12L.

[0032] In the above, the thickness TH of the retainer 12R is set to, for example, 0.5 mm, but the thickness TH may be set to a value other than 0.5 mm. For example, the thickness TH of the retainers 12L, 12R is preferably set to a value within the range of 40% to 90% of the gap GP between the first rail 4R and the second rail 5R.

[0033] 2. Effects of the Embodiment As described above, the bearing mechanism 1 according to this embodiment has rolling bearings 6L, 6R and plain bearings 7L, 7R arranged on both front-to-rear sides of the rolling bearings 6L, 6R between the first rails 4L, 4R and the second rails 5L, 5R. As a result, for example, during fast forward of the equipment or under light load, the relative movement between the first rails 4L, 4R and the second rails 5L, 5R is primarily borne by the rolling bearings 6L, 6R, thereby achieving operation without stick-slip. Furthermore, for example, during rapid acceleration / deceleration, under heavy load, or when subjected to loads accompanied by vibration, the relative movement between the first rails 4L, 4R and the second rails 5L, 5R is borne by both the rolling bearings 6L, 6R and the plain bearings 7L, 7R, thereby achieving operation without billowing. In this embodiment, the lubricant 13 is supplied to the plain bearings 7L, 7R in conjunction with the movement of the table 3 by the rolling bearings 6L, 6R. This allows a sufficient amount of lubricant 13 to be supplied to the plain bearings 7L, 7R, ensuring good oil film formation in the plain bearings 7L, 7R. This allows the bearing mechanism 1, which includes both a rolling bearing and a plain bearing, to operate smoothly.

[0034] Furthermore, this embodiment particularly provides the following effect. That is, when the table 3 moves, the plain bearings 7L, 7R located on the side opposite the direction of movement of the table 3 come into contact with the guide grooves 8L, 8R of the first track rails 4L, 4R that were located inside the table 3, whereas the plain bearings 7L, 7R located on the side toward the direction of movement of the table 3 come into contact with the guide grooves 8L, 8R of the first track rails 4L, 4R that were located outside the table 3. This tends to result in an insufficient supply of lubricant 13 to the plain bearings 7L, 7R located on the side toward the direction of movement of the table 3. In this embodiment, the lubricant 13 is supplied to the plain bearings 7L, 7R located on the side toward the direction of movement of the table 3 in conjunction with the movement of the table 3 by the rolling bearings 6L, 6R, so that a sufficient supply of lubricant can be made to the plain bearings 7L, 7R on both sides in the direction of movement of the table 3, regardless of the direction of movement of the table 3.

[0035] Furthermore, particularly in this embodiment, for example, when the table 3 moves forward, the rolling elements 9 roll relative to the guide grooves 8L, 10L and the guide grooves 8R, 10R, causing the retainers 12L, 12R to move forward by half the amount of movement of the table 3. Conversely, when the table 3 moves rearward, the rolling elements 9 roll relative to the guide grooves 8L, 10L and the guide grooves 8R, 10R, causing the retainers 12L, 12R to move rearward by half the amount of movement of the table 3. In this way, the rolling elements 9 that move inside the guide grooves 8L, 10L and the guide grooves 8R, 10R in conjunction with the movement of the table 3 pressure-feed the lubricant 13 contained inside the guide grooves 8L, 10L and the guide grooves 8R, 10R to the plain bearing portions 7L, 7R as the table 3 moves. This allows lubricant 13 to be supplied to the sliding bearing portions 7L, 7R located in the direction of movement of the table 3 in conjunction with the movement of the table 3 without providing a power source for supplying the lubricant 13.

[0036] Furthermore, this embodiment particularly provides the following effects. That is, to ensure smooth operation of a bearing mechanism 1 equipped with both a rolling bearing and a plain bearing, it is extremely important to not only ensure good oil film formation in the plain bearings 7L, 7R, but also to adjust the gaps between the first rails 4L, 4R and the second rails 5L, 5R (the preload of the plain bearings 7L, 7R). In this embodiment, the preload of the plain bearings 7L, 7R and the rolling bearings 6L, 6R can be easily adjusted and fixed using the preload adjustment screws 15 and the fixing screws 16, thereby enabling smooth operation of the bearing mechanism 1. Furthermore, preload management according to the usage conditions becomes possible.

[0037] 3. Modifications The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit and technical concept of the present invention. Such modifications will be described below.

[0038] (3-1. When a sealing member is provided) A sealing member may be provided between the rolling bearings 6L, 6R and the plain bearings 7L, 7R. The configuration of a bearing mechanism 1A according to this modified example will be described using Figures 10 and 11. Figure 10 is a perspective view showing the overall configuration of the bearing mechanism 1A according to this modified example, and Figure 11 is a cross-sectional view taken along line XI-XI in Figure 10, showing the cross-sectional structure of the second raceway, plain bearing, and sealing member. Note that the base 2, table 3, etc. are not shown in Figure 11.

[0039] As shown in Figures 10 and 11, a seal member 17L is provided between the rolling bearing 6L and the plain bearing 7L. The seal member 17L includes a seal member 17Lf arranged between the rolling bearing 6L and the front plain bearing 7Lf, and a seal member 17Lb arranged between the rolling bearing 6L and the rear plain bearing 7Lb. The seal member 17Lf is formed in a substantially rectangular frame shape and is provided to surround the outer periphery of the rear end of the substantially rectangular prism-shaped plain bearing 7Lf. The seal member 17Lb is formed in a substantially rectangular frame shape and is provided to surround the outer periphery of the front end of the substantially rectangular prism-shaped plain bearing 7Lb. The installation structure of the seal member 17L is not particularly limited, and it may be installed, for example, as follows. That is, as shown in Figure 11, the second track rail 5L may be divided into three parts, for example, a front part 5La in which the plain bearing portion 7Lf is provided, a central part 5Lb in which the lubricant reservoir 14L is provided, and a rear part 5Lc in which the plain bearing portion 7Lb is provided, and after sealing members 17Lf, 17Lb are installed in the recesses at both ends of the central part 5Lb, the front part 5La and the rear part 5Lc may be connected to the central part 5Lb.

[0040] The seal members 17Lf, 17Lb each have a shape in which the inner circumferential side is bent toward the plain bearings 7Lf, 7Lb, so that the seal members 17Lf, 17Lb are configured to have higher rigidity against deformation that causes the lubricant 13 to infiltrate from the plain bearings 7Lf, 7Lb into the lubricant reservoir 14L (rolling bearing 6L) than the rigidity against deformation that causes the lubricant 13 to infiltrate from the lubricant reservoir 14L (rolling bearing 6L) into the plain bearings 7Lf, 7Lb.

[0041] Although not shown, a seal member 17R having the same configuration as the seal member 17L is also provided between the rolling bearing portion 6R and the plain bearing portion 7R.

[0042] According to this modification, after the lubricant 13 is supplied from the lubricant reservoirs 14L, 14R to the plain bearings 7L, 7R by pressure transfer using the rolling elements 9, the seal members 17L, 17R can prevent the lubricant 13 from returning from the plain bearings 7L, 7R to the lubricant reservoirs 14L, 14R. This allows the lubricant 13 to be effectively used to form an oil film in the plain bearings 7L, 7R, reducing the amount of lubricant 13 used and the environmental impact.

[0043] (3-2. When Crowning the Plain Bearings) The clearance between the plain bearings 7L, 7R and the first raceways 4L, 4R is extremely important. On the other hand, while the rolling bearings 6L, 6R provide high precision and light movement with little stick-slip, they tend to deform significantly due to deformation of the rolling elements 9. Therefore, by applying R-chamfering and crowning to both ends of the plain bearings 7L, 7R that abut against the first raceways 4L, 4R in accordance with the amount of deformation of the rolling bearings 6L, 6R, the locking phenomenon of the plain bearings under high loads can be eliminated, resulting in smooth sliding. For example, the end faces of the plain bearings 7Lf, 7Lb facing the first raceway 4L may be subjected to R-chamfering or crowning grinding so that the distance from the end faces of the guide grooves 8L of the first raceway 4L gradually increases toward the ends on both sides in the front-rear direction. Similarly, the end faces of the plain bearing portions 7Rf, 7Rb facing the first track rail 4R may be subjected to R-chamfering or crowning grinding so that the distance from the end face of the guide groove 8R of the first track rail 4R gradually increases towards both ends in the front-to-rear direction.

[0044] According to this modification, tapered reliefs can be formed in the plain bearings 7L, 7R to accommodate the elastic deformation of the rolling elements 9 of the rolling bearings 6L, 6R. This makes it possible to bring the first raceways 4L, 4R and the plain bearings 7L, 7R into contact with each other without any gaps (so-called solid contact) even when a moment load or the like acts on the table 3, thereby improving vibration absorption.

[0045] (3-3. When a mechanism to prevent retainer slippage is provided) As described above, as the table 3 moves forward and backward within the stroke range, the retainers 12L, 12R move forward and backward by half the amount of movement of the table 3. For this reason, as the table 3 moves repeatedly, the retainers 12L, 12R may become misaligned from their initially set positions.

[0046] Therefore, in this modified example, as shown in Figure 12, protrusions 19 are formed at a predetermined pitch on the outer peripheral surface of at least one of the plurality of rolling elements 9a, 9b (one rolling element 9a in Figure 12). Furthermore, dimple holes 20 into which the protrusions 19 of the rolling element 9a fit are formed on the rolling surfaces 8L1 or 8L2 and 8R1 or 8R2 of the guide grooves 8L, 8R of the first raceways 4L, 4R, and on the rolling surfaces 10L1 or 10L2 and 10R1 or 10R2 of the guide grooves 10L, 10R of the second raceways 5L, 5R. The dimple holes 20 are formed so that the protrusions 19 can engage with them to allow the rolling elements 9 to roll smoothly. 12 shows, as an example, a structure in which the protrusions 19 of the rolling elements 9a of the retainer 12L fit into the dimple holes 20 of the rolling surfaces 8L1 and 10L2, but similarly, the protrusions 19 of the rolling elements 9a of the retainer 12R fit into the dimple holes 20 of the rolling surfaces 8R1 and 10R2. Also, the retainer 12L is not shown in FIG.

[0047] This makes it possible to prevent slippage between the retainers 12L, 12R and the first raceway rails 4L, 4R and the second raceway rails 5L, 5R, and to prevent misalignment of the retainers 12L, 12R.

[0048] The cutting of the dimple holes 20 into each rolling surface is performed before the rolling surfaces are hardened. That is, if the cutting of the dimple holes 20 is performed after the rolling surfaces are hardened, for example, the hardness of each rolling surface will increase, which will result in a problem of time-consuming cutting using an end mill or the like and poor cutting efficiency. In this embodiment, by cutting the dimple holes 20 into each rolling surface before hardening, it is possible to cut the dimple holes before the hardness increases. This improves cutting efficiency and reduces costs.

[0049] In the above description, the rolling elements 9 are provided with the projections 19 and the rolling surfaces are formed with the dimpled holes 20. However, the mechanism for preventing the retainers 12L, 12R from shifting is not limited to this. For example, the retainers 12L, 12R may be prevented from shifting by a rack and pinion mechanism.

[0050] (3-4. When packing to prevent leakage of lubricant is provided) Packing may be provided to prevent leakage of lubricant 13 from the gap GP between the first rails 4L, 4R and the second rails 5L, 5R. This modification will be described with reference to FIG.

[0051] The bearing mechanism 1 according to this modified example has retainers 21L and 21R. The retainer 21L is disposed between the first and second rails 4L and 5L so as to be movable in the front-rear direction. The retainer 21R is disposed between the first and second rails 4R and 5R so as to be movable in the front-rear direction. FIG. 13 shows an example of the structure of the retainer 21L. As shown in FIG. 13, the retainer 21L has a support portion 21La and a packing portion 21Lb. The support portion 21La is formed in a substantially rectangular prism shape, and its cross-sectional area perpendicular to the front-rear direction is smaller than or equal to the cross-sectional area of ​​the lubricant reservoir 14L. The length L8 in the front-rear direction of the support portion 21La is substantially the same as the length L2 in the front-rear direction of the retainer 12L in the previously described embodiment. The support portion 21La rotatably holds the multiple rolling elements 9 so that the rolling elements 9a and 9b, whose rotation axis directions are approximately 90 degrees apart, are arranged alternately in the front-to-rear direction and so that adjacent rolling elements 9a, 9b do not come into contact with each other. The rolling elements 9a, 9b are provided so that a portion of their surfaces that come into contact with the rolling surfaces is exposed from the surface of the support portion 21La. Lubricant guide grooves 23 may be formed on the surfaces of the support portion 21La that face the rolling surfaces 8L1, 8L2 of the first track rail 4L and the rolling surfaces 10L1, 10L2 of the second track rail 5L.

[0052] Two packing portions 21Lb are provided on both the upper and lower sides of the support portion 21La, extending in the front-rear direction. The packing portions 21Lb are sheet-like members elongated in the front-rear direction, and their thickness is approximately the same as the thickness TH of the retainers 12L and 12R. The front-rear length L9 of the portion of the packing portion 21Lb protruding forward from the support portion 21La is configured to be approximately the same as or shorter than the front-rear length L1 of the plain bearing portion 7Lf. Similarly, the front-rear length L10 of the portion of the packing portion 21Lb protruding rearward from the support portion 21La is configured to be approximately the same as or shorter than the front-rear length L1 of the plain bearing portion 7Lb. A V-shaped bearing guide groove 24 is formed on the inner edges of the portions of the two packing portions 21Lb protruding forward and rearward from the support portion 21La, facing each other. The upper and lower ends of the plain bearing portions 7Lf and 7Lb fit into the bearing guide grooves 24. Specifically, when the table 3 moves to the front stroke end as shown in Figures 4 and 5, the portion of the packing portion 21Lb protruding forward from the support portion 21La fits into almost the entire upper and lower ends of the plain bearing portion 7Lf, and at least a portion of the portion of the packing portion 21Lb protruding rearward from the support portion 21La fits into the upper and lower ends of the plain bearing portion 7Lb. Furthermore, when the table 3 moves to the rear stroke end as shown in Figures 6 and 7, the portion of the packing portion 21Lb protruding rearward from the support portion 21La fits into almost the entire upper and lower ends of the plain bearing portion 7Lb, and at least a portion of the portion of the packing portion 21Lb protruding frontward from the support portion 21La fits into the upper and lower ends of the plain bearing portion 7Lf.

[0053] Although not shown, the retainer 21R has the same configuration as the retainer 21L described above.

[0054] 2 and 3, when the table 3 moves from a state in which it is positioned at the center of its stroke to a state in which it is positioned at the front stroke end as shown in Figures 4 and 5, the rolling bearings 6L, 6R, including the retainers 21L, 21R and the rolling elements 9, move forward by half the amount of movement of the table 3, so that the front ends of the support portions 21La, 21Ra of the retainers 21L, 21R and the rear ends of the plain bearings 7Lf, 7Rf are approximately aligned. As a result, the support portions 21La, 21Ra, which move forward inside the guide grooves 8L, 10L and 8R, 10R in conjunction with the forward movement of the table 3, pressure-feed the lubricant 13 contained in the lubricant reservoirs 14L, 14R to the plain bearings 7Lf, 7Rf, which are positioned at the front, in the direction of movement of the table 3. At this time, packing portions 21Lb, 21Rb prevent leakage of lubricant 13 from the gap GP between the first track rails 4L, 4R and the second track rails 5L, 5R. The lubricant 13 pumped to the plain bearing 7Lf is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Lf and the guide groove 8L, and the lubricant 13 pumped to the plain bearing 7Rf is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Rf and the guide groove 8R. Of the pumped lubricant 13, any excess lubricant 13 other than the lubricant 13 supplied to the plain bearings 7Lf, 7Rf moves via lubricant guide grooves 23 formed in the supports 21La, 21Ra to the space behind the rolling bearings 6L, 6R in the lubricant reservoirs 14L, 14R.

[0055] 2 and 3 to the rear stroke end as shown in Figures 6 and 7, the rolling bearings 6L, 6R including the retainers 21L, 21R and the rolling elements 9 move rearward by half the amount of movement of the table 3, so that the rear ends of the support portions 21La, 21Ra of the retainers 21L, 21R and the front ends of the plain bearings 7Lb, 7Rb are aligned. As a result, the support portions 21La, 21Ra, which move rearward inside the guide grooves 8L, 10L and 8R, 10R in conjunction with the rearward movement of the table 3, pressure-feed the lubricant 13 contained inside the lubricant reservoirs 14L, 14R to the plain bearings 7Lb, 7Rb located on the rear side, in the direction of movement of the table 3. At this time, packing portions 21Lb, 21Rb prevent leakage of lubricant 13 from the gap GP between the first track rails 4L, 4R and the second track rails 5L, 5R. The lubricant 13 pumped to the plain bearing 7Lb is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Lb and the guide groove 8L, and the lubricant 13 pumped to the plain bearing 7Rb is supplied to the lubricant supply groove 11 on the sliding surface between the plain bearing 7Rb and the guide groove 8R. Of the pumped lubricant 13, any excess lubricant 13 other than that supplied to the plain bearings 7Lb, 7Rb moves via lubricant guide grooves 23 formed in the supports 21La, 21Ra to the space in front of the rolling bearings 6L, 6R in the lubricant reservoirs 14L, 14R.

[0056] According to the modified example described above, it is possible to effectively prevent leakage of lubricant 13 from the gap GP between the first rails 4L, 4R and the second rails 5L, 5R, and the retainers 21L, 21R sandwiched between the first rails 4L, 4R and the second rails 5L, 5R can stroke with an appropriate clearance.

[0057] (3-5. Others) In the above, a linear guide mechanism that moves the table 3 linearly relative to the base 2 has been described as an example of a bearing mechanism, but the present invention is not limited to this. For example, the present invention may be applied to a curved guide mechanism that moves the table 3 in a curved line, such as a circular arc or wave shape, relative to the base 2. In this case, the first and second track rails may be curved members. Furthermore, the bearing mechanism may be a mechanism in which a cylindrical second track rail moves linearly relative to a shaft-shaped first track rail (a so-called finite stroke rolling bearing). In this case, components such as the base 2 and table 3 are not required.

[0058] Furthermore, although the above description has been given of a case in which two first rails 4L, 4R are installed on the base 2, this is not limitative. For example, one first rail may be installed on the base 2, with the rolling bearings 6L, 6R and the plain bearings 7L, 7R disposed between the left and right side surfaces of the first rail and the second rails 5L, 5R. Even when the present invention is applied to a bearing mechanism configured in this manner, the same effects as those of the above embodiment can be obtained.

[0059] Furthermore, if the length of the first rail is long, a plurality of first rails may be connected in series.

[0060] In addition to the above, the methods according to the above embodiments and modifications may be used in appropriate combination.

[0061] Although not specifically illustrated, the present invention can be implemented with various modifications within the scope of the invention.

[0062] REFERENCE SIGNS LIST 1 Bearing mechanism 1A Bearing mechanism 2 Base 3 Table 4L First raceway 4R First raceway 5L Second raceway 5R Second raceway 6L Rolling bearing portion 6R Rolling bearing portion 7L Plain bearing portion 7Lb Plain bearing portion 7Lf Plain bearing portion 7R Plain bearing portion 7Rb Plain bearing portion 7Rf Plain bearing portion 8L Guide groove 8R Guide groove 9 Rolling element 9a Rolling element 9b Rolling element 10L Guide groove 10R Guide groove 12L Retainer 12R Retainer 13 Lubricant 15 Preload adjusting screw 16 Fixing screw 17L Seal member 17Lb Seal member 17Lf Seal member 17R Seal member 18L Lubricant supply portion 18R Lubricant supply portion 21L Retainer 21R retainer

Claims

1. A bearing mechanism, comprising: a first track stand; a second track stand shorter than the first track stand and moving relative to the first track stand; a rolling bearing portion disposed between the first track stand and the second track stand; a sliding bearing portion disposed between the first track stand and the second track stand in the axial direction of the rolling bearing portion; and a lubricant supply portion configured to supply lubricant to the sliding bearing portion in conjunction with the movement of the second track stand by the rolling bearing portion.

2. The bearing mechanism according to claim 1, wherein the lubricant supply portion supplies the lubricant to the sliding bearing portion located in the moving direction of the second track stand in conjunction with the movement of the second track stand by the rolling bearing portion.

3. The rolling bearing portion includes a plurality of rolling elements that contact guide grooves formed in the first track stand and the second track stand, and a retainer that is disposed between the first track stand and the second track stand so as to be axially movable and is formed shorter than the second track stand, and holds the plurality of rolling elements. The lubricant supply portion is configured such that the rolling elements moving inside the guide grooves in conjunction with the movement of the second track stand pump the lubricant accommodated inside the guide grooves to the sliding bearing portion located on the movement direction side of the second track stand. The bearing mechanism according to claim 2, characterized in that.

4. The bearing mechanism according to any one of claims 1 to 3, wherein the sliding bearing portion is subjected to R chamfering and crowning processing according to the deformation amount of the rolling bearing portion at both axial ends in contact with the first track stand.

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