BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a partially cutaway side view of an embodiment of a linear guide apparatus of the invention;
FIG. 2 is a side view which describes a modified example (having two rolling element rolling grooves) of the invention;
FIG. 3 is a side view which describes a modified example (in which either of rolling element rolling grooves has a cross section which is formed substantially into an ark-like shape of quarter of a circle) of the invention;
FIG. 4 is a side view which describes a modified example (in which both of rolling element rolling grooves have a cross section which is formed substantially into an ark-like shape of quarter of a circle) of the invention;
FIG. 5 is a side view which describes a modified example (in which a scoop-up portion of the type shown in FIG. 4 is not provided) of the invention;
FIG. 6 is a side view which describes a modified example (having a guide rail of a different shape) of the invention;
FIG. 7 is a side view which describes a modified example (in which a scoop-up portion of the type shown in FIG. 6 is not provided) of the invention;
FIG. 8 is a table which describes test conditions of a test carried out on end caps made from resins having different izod impact strengths with notch;
FIG. 9 is a graph which shows a relationship between izod impact strengths with notch of the end caps and sliding distances of sliders;
FIG. 10 is a table which describes test conditions of a test carried out on guide rails having rolling element rolling grooves which are different in shape; and
FIG. 11 is a graph which shows a relationship between the shapes of the rolling element rolling grooves and sliding distances of sliders.
DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS
Hereinafter, embodiments of a linear guide apparatus of the invention will be described based on the accompanying drawings
<Configuration of Linear Guide Apparatus>
FIG. 1 is a partially cutaway side view which shows a linear guide apparatus of an embodiment of the invention.
As shown in FIG. 1, a linear guide apparatus 1 is configured to include a guide rail 2 which extends linearly, a slider 3 having a rolling element rolling groove which faces a rolling element rolling groove on the guide rail 2 and provided in such a manner as to straddle the guide rail 2, a rolling element rolling path 4 made up of the rolling element rolling groove (having a cross section which is formed substantially into an arc shape of a half of a circle) formed on a side surface of the guide rail 2 and the rolling element rolling groove formed on an internal side surface of the slider 3 in such a manner as to face the rolling element groove on the guide rail 2 and a plurality of rolling elements 5 inserted into the rolling element rolling path 4 in such a manner as to roll freely therein, whereby the slider 3 is made to shift relatively along longitudinal direction of the guide rail 2.
In addition, the slider 3 is configured to include a slider main body 3a having a rolling element return path 6 which passes through the slider main body 3a between end faces thereof and end caps 3b made from a resin (that is, a resin having an izod impact strength with notch of 10.5 kJ/m2 or more) which each have a curved direction turning path adapted to connect the corresponding rolling element rolling path 4 with the rolling element return path 6 and which are fixed to end faces of the slider main body 3a, respectively.
As a material for the end caps 3b, for example, when POM is used, Delrin 100 from DuPont or products in similar models or similar products can be raised.
Additionally, a scoop-up portion 7 for scooping up the rolling elements is formed on the end cap 3b so as to guide the rolling elements 5 which roll in the rolling element rolling path 4 into the rolling element return path 6 in a smooth fashion.
In this way, in the linear guide apparatus of this embodiment, since the end caps 3b are made from the resin having the izod impact strength with notch of 10.5 kJ/m2 or more, the occurrence of damages such as chipping or cracking to the end caps 3b can be prevented, thereby making it possible to enhance the durability of the end caps 3b when the linear guide apparatus is driven at high speeds.
In addition, in this embodiment, while the example is described in which the rolling element rolling groove is provided in the vicinity of a central portion of the side surface of the guide rail 2, the invention is not limited thereto. For example, as shown in FIG. 2, rolling element rolling grooves may be provided in two upper and lower locations on the side surface of the guide rail 2, for example.
Additionally, in a case where rolling element rolling grooves are provided in two upper and lower locations on the side surface of the guide rail 2, for example, as shown in FIGS. 3 to 7, at least either of the two upper and lower rolling element rolling grooves may be formed to have a cross section which is formed substantially into an arc shape of quarter of a circle. By adopting this configuration, the rolling element rolling groove on the slider main body 3a is formed to have a cross section which is formed substantially into an arc shape of three-quarter of a circle, so as to increase the holding amount of the rolling elements by the slider main body 3a, whereby the rolling elements 5 can be guided smoothly into the rolling element return path 6 from the rolling element rolling path 4, thereby making it possible to reduce impact to the scoop-up portion 7 (with an end cap 3b having no scoop-up portion 7 formed thereon, impact to the end cap 3b). In addition, as shown in FIGS. 3, 4 and 6, since the protruding amount of the scoop-up portion 7 can be decreased, bending stress can be decreased which would otherwise be produced when the scoop-up portion 7 is struck by the rolling elements 5.
<Example>
Next, the results of a sliding distance test in which the linear guide apparatus according to the embodiment was driven at high speeds will be described based on the drawings.
Firstly, as shown in FIG. 8, #55 standard linear guide apparatuses were made by employing four types of resin end caps having different izod impact strength with notch (that is, resin end caps having, respectively, izod impact strength with notch of 7 kJ/m2, 9 kJ/m2, 12 kJ/m2, 90 kJ/m2) and a test was carried out in which sliding distances of sliders were measured until the end caps were broken, whereby the sliders were unable to slide any longer under test conditions in which the sliding speed was 300 m/min, an AS2 grease was used as a lubricant, rolling elements having a diameter of 9.525 mm were used, and the temperature was 23° C. FIG. 9 is a graph showing the result of analysis of the test results in the form of a relationship between izod impact strengths with notch of the respective end caps and sliding distances of the respective sliders.
According to the graph, it is seen that the sliding distance of the slider starts to increase drastically as the izod impact strength with notch of the resin of the end cap increases substantially from a point where the izod impact strength with notch of 5 kJ/m2 is surpassed and becomes sufficiently when the izod impact strength with notch has reached 10.5 kJ/m2.
In addition, similarly, it is seen that when the izod impact strength with notch surpasses 10.5 kJ/m2, the increase in sliding distance of the slider reaches a saturated state and that the sliding distance is not increased so much as the increase in izod impact strength with notch.
In addition, in this case, since deformation becomes easy to be produced when the end caps are fixed with machine screws with a small bending elastic modulus, a bending elastic modulus of 2,000 MPa or greater is desirable.
In addition, as shown in FIG. 10, a test was carried out on #55 standard linear guide apparatuses which were made up of end caps of izod impact strength with notch of 12 kJ/m2 (10.5 kJ/m2 or greater) and guide rails having rolling element rolling grooves which are different in shape (that is, guide rails having rolling element rolling grooves which are formed to have cross sections which are formed substantially into arc shapes of a half and quarter of a circle, respectively) in which sliding distances of sliders were measured until the end caps were broken, whereby the sliders were unable to slide any longer under test conditions in which the sliding speed was 300 m/min, an AS2 grease was used as a lubricant, rolling elements having a diameter of 9.525 mm were used, and the temperature was 23° C. FIG. 11 is a graph showing the result of analysis of the test results in the form of a relationship between the shapes of the respective rolling element rolling grooves and sliding distances of the respective sliders.
Namely, it is seen that the end caps are made more difficult to be damaged with the rolling element rolling groove of the ark-like shape of quarter of a circle than the rolling element rolling groove of the ark-like shape of a half of a circle.
While the invention has been described in connection with the exemplary embodiments, it will be obvious to those skilled in the art that various changes and modification may be made therein without departing from the present invention, and it is aimed, therefore, to cover in the appended claim all such changes and modifications as fall within the true spirit and scope of the present invention.
Patent Application
20080078096
