WO2011052231A1

WO2011052231A1 - Hybrid guide apparatus for machine tools

Info

Publication number: WO2011052231A1
Application number: PCT/JP2010/006418
Authority: WO
Inventors: Koji Nishii
Original assignee: Kiwa Machinery Co., Ltd.
Priority date: 2009-10-30
Filing date: 2010-10-29
Publication date: 2011-05-05
Also published as: JP2012192461A

Abstract

The guide apparatus for a machine tool including a guide unit that supports a movable member, a guide rail which is inserted into said guide unit, said guide rail having a guide surface extending along said guide rail, the press member that projects from a position displaced from the guide surface to a position to press the guide surface, said press member having a sliding guide surface that is capable of pressing the guide surface with regard to the movable member.

Description

HYBRID GUIDE APPARATUS FOR MACHINE TOOLS

The present invention relates to a guide apparatus for machine tools. The present invention, especially, relates to the hybrid guide apparatus for machine tools into which rolling and sliding guides are combined.

The conventional type of the guide apparatus for machine tools is described as follows. The guide apparatus for machine tools can reduces a friction force during the movement of a moving member. In general, in this case, either one of rolling and sliding guides is used for machine tools as a guide apparatus.

With reference to Figs. 5A and 5B, the conventional type of the rolling guide for machine tools is explained in detail as below. Fig. 5A shows the conventional type of a guide apparatus for machine tools. Fig. 5B shows an enlarged cross section view of the dashed line portion 5B at the guide rail 53 in Fig. 5A. On the two

guide rails

53 and 54 provided horizontally and in parallel on the bed 50 arranged on the base (not shown), a movable member 51 is provided to bridge the two

guide rails

53 and 54. The movable member 51 on the side of the guide rail 53 has

guide units

52a and 52b. The movable member 51 on the other side that is on the side of the guide rail 54 has also guide units in the same manner. With reference to Fig. 5B, the guide unit 52a is explained as a typical example below. The other guide units are the same. The guide rail 53 is inserted in the guide unit 52a as shown in Fig. 5B. The movable member 51 is slidable on the guide rail 53 while keeping its attitude. Accordingly, the positions at which the

guide units

52a and 52b are arranged are determined according to their sizes and weights so as to keep the most appropriate balance. For example, in the view on a side of the guide rail 53, the positions of the

guide units

52a, 52b are determined to keep symmetry with regard to the center line of the dimension in the longitudinal direction of the movable member 51, along the longitudinal direction of the guide rail 53. The guide units on the other side as the side of the guide rail 54 are also arranged in the same manner. The portion under the movable member 51 has a ball screw along the

guide rails

53 and 54 whereby the movable member 51 is capable of sliding along the

guide rails

53 and 54.

The movable member 51 can be used for all sliding members of a sliding device in a machine tool, e.g. a machine table, the base member of a machine table, a spindle, a compound tool rest, a saddle, a column, or the like. As long as a member in a machine tool moves in a direction, the movable member 51 can be used. In this specification and claims, the term, "movable member", implies sliding members in a machine tool, e.g. a machine table, the base member of a machine table, a spindle, a compound tool rest, a saddle, a column, or the like. Therefore, in this application, "sliding member" is used as a term for all of sliding members of a sliding device in a machine tool.

With reference to Fig. 5B, the guide unit 52a is described below. As shown in Fig. 5B, in the guide unit 52a, the predetermined type of a circular groove is provided. In the circular groove, a plural of rolling members are continuously arranged so as to form

rolling member lines

55a, 55b like chains. A roller (cylinder-type-member) or bearing (ball-type-member) can be applied to as a rolling member. Various types of arrangements of the circular grooves can be applied, and in Fig. 5B as an example, circular grooves are provided so that a surface formed by rolling members of the rolling member line 55a and a surface formed by rolling members of the rolling member line 55b intersect with an arbitrarily defined angle. The side surfaces of the guide rail 53 form recess-side-surfaces that are depressed in the surface extending in the longitudinal direction of the guide rail 53. For example, one of the recess-side-surfaces includes the sliding surface 53a and the sliding surface 53b in the longitudinal direction of the guide rail 53. The circular grooves on the

sliding surfaces

53a and 53b open on the sides on the

sliding surfaces

53a and 53b to expose the groups of the rolling members of the

rolling member lines

55a and 55b. By this, the rolling members of the

rolling member lines

55a and 55b are capable of contacting the

sliding surfaces

53a and 53b. By this structure, in the case where the guide unit 52a moves along the guide rail 53, the rolling members of the rolling member lines 55a move and circulate in the circular groove while rolling on the sliding surface 53a. Also, in the same manner, the rolling members of the rolling member lines 55b move and circulate in the circular groove while rolling on the sliding surface 53b. The rolling of the

rolling member lines

55a and 55b on the

sliding surfaces

53a and 53b achieves smooth movement of the guide unit 52a with regard to the guide rail 53.

In the same way, on the other recess-surface of the guide rail 53, the

sliding surfaces

53c and 53d are symmetrically provided with regard to the

sliding surfaces

53a and 53b along the longitudinal direction of the guide rail 53. The guide unit 52a on the sides of sliding

surfaces

53c and 53d also has circular grooves and rolling member lines (not shown).

Next, with reference to Fig. 6A, the conventional type of a sliding guide for machine tools is explained as below. Fig. 6A shows a conventional type of a sliding guide for machine tools. Fig. 6B shows a cross section 6B-6B at the portion of the guide rail 56. In the same manner as the aforementioned rolling guides, the movable member 51 are placed on the two

parallel guide rails

56 and 57 to bridge them, wherein the two

parallel guide rails

56 and 57 are horizontally placed on the bed 50 provided on the base (not-shown). The

guide rails

56 and 57 have extending

portions

56a and 57a each extending from the width of each of the

guide rails

56 and 57. The movable member 51 on the side of the guide rail 56 has a protruding portion 58a that surrounds and holds the extending portion 56a of the guide rail 56. The other side of the movable member 51 on the side of the guide rail 57 has a protruding portion 58b that surrounds the extending portion 57a of the guide rail 57. The extending portion 56a is supported between a surface of the movable member and the protruding portion 58a, while the extending portion 57a is supported between a surface of the movable member and the protruding portion 58b.

Quench-hardening and grinding treatment is applied to the guide surface 56b on the side of the guide rail 56 contacting the movable member 51 to reduce a friction force in the case of sliding the movable member 51.

A polyester plastic resin plate is attached on the guide surface 51a on the side of the movable member 51 that faces to the guide surface 56b on the side of the guide rail 56. Scraping process is performed on the surface of the polyester plastic resin plate, wherein the surface of the polyester plastic resin plate contacts the guide surface 56b of the guide rail 56. The same processing is also applied to the contact surfaces between the extending portion 56a of the guide rail 56 and the movable member 51 and between the extending portion 56a and the protruding portion 58a. The movable member 51 is capable of moving smoothly with regard to the

guide rails

56 and 57.

In comparison of the performance between the rolling and the sliding guides, the sliding guide is unsuitable for high-speed movement and has disadvantages of high-cost and relatively lower positioning-accuracy than that of the rolling guide. In addition, especially, because the difference between the static friction coefficient in the case of starting movement and the kinematics friction coefficient during movement is huge, there is a disadvantage in which the circularity on the work in the circular-arc-cutting process is degraded.

In contrast, rolling guides are suitable for high-speed movement and have advantages of low-cost and relatively higher positioning-accuracy than that of the sliding guide. With regard to vibration caused in cutting process, dumping performance of rolling guides for the vibration is lower than that of sliding guides. In addition, generally, cutting accuracy of rolling guides is lower than that of sliding guides. Therefore, for example, as disclosed in Patent Literature 1 and Patent Literature 2, the hybrid guide apparatus for machine tools into which rolling and sliding guides are combined is proposed.

PTL 1: Japanese Patent Application Laid-Open No. 2003-326430
PTL 2: Japanese Patent Application Laid-Open No. 2004-421869
PTL 3: Japanese Patent No. 4218831

In the hybrid guide apparatus for machine tools, however, it is difficult to switch a guide apparatus between rolling and sliding types. For example, in Patent Literature 1, rolling and sliding guides are switched by attaching or displacing a block member having a sliding guide surface. In Patent Literature 2, rolling and sliding guides cannot be arbitrarily switched.

In this context, these days, in various technical fields, the surface treatment in which the surface is coated with Diamond-Like-Carbon (hereinafter referred to as "DLC") is frequently used for technology to decrease a friction force. This treatment is also expected for the surface treatment of sliding guide apparatuses for machine tools. For example, as disclosed in Patent Literature 3, the coating processing of a guide surface for machine tools on which DLC is coated improves a friction coefficient on a guide surface and a positioning accuracy.

Therefore, the hybrid guide apparatus for machine tools which takes advantage of rolling and sliding guides are desired.

A purpose of the invention is to provide a guide apparatus to bring out both advantages of rolling and sliding guides according to an object for or a condition of cutting.

Another purpose of the present invention is to provide a guide apparatus for a machine tool including a guide unit that supports a movable member, a guide rail which is inserted into the guide unit, the guide rail having a guide surface extending along the guide rail, press member that projects from a position displaced from the guide surface to a position to press the guide surface, the press member having a sliding guide surface that is capable of pressing the guide surface with regard to the movable member, wherein the guide unit includes a line group of bearing members to slide the guide unit along the guide rail, wherein the press member presses the guide surface with the sliding guide surface with a predetermined pressing force and the sliding surface of the press member slides on the guide surface so that the guide unit is slidable along the guide rail.

A further purpose of the invention is to provide a guide apparatus for a machine tool, including a first guide unit that supports a movable member, a second guide unit that supports the movable member of the first guide unit under the first guide unit, a guide rail that is inserted into the first guide unit and second guide unit, the guide rail having a guide surface extending along the guide rail, a first press member that projects from a position displaced from the guide surface to a position to press the guide surface, the first press member having a first sliding guide surface that is capable of pressing the guide surface with regard to the movable member, a second press member that projects from a position displaced from the guide surface to a position to press the guide surface, the second press member having a second sliding guide surface that is capable of pressing the guide surface with regard to the movable member, wherein each of the first and second guide units includes a line group of bearing members to slide the first and second guide units along the guide rail, wherein the first press member presses the guide surface with the first sliding guide surface with a first pressing force and the second press member presses the guide surface with the second sliding guide surface with a second pressing force, and the first and second sliding surfaces of the first and second press members slide on the guide surface so that the first and second guide units are slidable along the guide rail.

A still further purpose of the invention will be apparent by the following description and the accompany drawings.

In the present invention, advantages of rolling and sliding guides can be effected according to the object and the condition in the cutting processes.

Fig. 1A shows a perspective view of the first embodiment of the hybrid guide apparatus for machine tools. Fig. 1B shows a cross section view of the hybrid guide apparatus for machine tools along the guide rail as the first embodiment. Fig. 1C shows a cross section view of the hybrid guide apparatus for machine tools in a direction perpendicular to the longitudinal direction of the guide rail as the first embodiment. Fig. 2A shows a cross section view of the hybrid guide apparatus for machine tools at the portion 2A-2A of Fig. 2C in the case where the rollers are used. Fig. 2B shows a cross section view of the hybrid guide apparatus for machine tools in the case where the roller and the sliding guides are used. Fig. 3A shows a perspective view of the hybrid guide apparatus for machine tools as the second embodiment. Fig. 3B shows a view of the hybrid guide apparatus for machine tools in the arrowed direction 3B of Fig. 3A. Fig. 4 shows a view of the hybrid guide apparatus for machine tools as the third embodiment. Fig. 5A shows a perspective view of the conventional type of rolling guide apparatus for machine tools. Fig. 5B shows a cross section view of the conventional type of rolling guide apparatus for machine tools. Fig. 6A shows a perspective view of the conventional type of sliding guide apparatus for machine tools. Fig. 6B shows a cross section view of the conventional type of sliding guide apparatus for machine tools. Fig. 7A shows an example of the combinations of the first, second and third embodiment of the present invention. Fig. 7B shows an example of the combinations of the first, second and third embodiment of the present invention. Fig. 7C shows an example of the combinations of the first, second and third embodiment of the present invention. Fig. 7D shows an example of the combinations of the first, second and third embodiment of the present invention. Fig. 7E shows an example of the combinations of the first, second and third embodiment of the present invention. Fig. 7F shows an example of the combinations of the first, second and third embodiment of the present invention.

With reference to Figs. 1A to 1C and Figs. 2A to 2B, the first embodiment of the hybrid guide apparatus for machine tools 1 is described as below.

First Embodiment

Fig. 1A shows a hybrid type of guide apparatus 1 as the first embodiment. Fig. 1B is a cross section view of the hybrid guide apparatus for machine tools along the guide rail as the first embodiment. Fig. 1C is a cross section viewed in the arrowed direction 1C. The guide apparatus 1 includes the

guide rails

3, 4, the

press members

5 and 6 and the guide unit 9 to 12.

The guide rails 3, 4 are horizontally provided on the bed 20 set on the base (not shown). The guide rail 4 is arranged in parallel to the guide rail 3. The guide rails 3, 4 have

guide surfaces

3a, 4a extending along the

guide rail

3, 4. In this embodiment, although the guide surfaces 3a and 4a are explained as the horizontal top surface that is parallel to the top surface of the bed 20, among the

guide rails

3 and 4, the guide surfaces 3a and 4a may be chosen on the other surfaces of the

guide rails

3 and 4.

The guide units 9 to 12 support the movable member 2. The guide units 9 to 12 are fixed with regard to the movable member 2 and skiable on the

guide rails

3 and 4 so that the movable member 2 is slidable along the

guide rails

3 and 4. The guide rail 3 is inserted into the

guide units

9 and 10, while the guide rail 4 is inserted into the

guide units

11 and 12. The guide units 9 to 12 are arranged on the

guide rails

3, 4 so that the movable member 2 bridges the

guide rails

3, 4. Although it is not shown in Figs. 1A to 1C, a ball screw is arranged along the

guide rails

3, 4 below the movable member 2, so that the movable member 2 is slidable along the

guide rails

3 and 4.

For example, as shown in Fig. 1C, the press member 5 is provided between the

guide units

9 and 10 on the side of the guide rail 3 and fixed with regard to the movable member 2. The other press member 6 is provided between the

guide units

11 and 12 on the side of the guide rail 4. The

press members

5 and 6 include the

guide members

7 and 8. The

guide members

7 and 8 respectively include the sliding guide surfaces 7aa and 8aa. The sliding guide surfaces 7aa and 8aa respectively face the guide surface 3a on the guide rail 3 and the guide surface 4a on the guide rail 4.

The sliding guide surfaces 7aa of the guide member 7 is capable of protruding from a retracting position spaced from the guide surface 3a of the guide rail 3 to a press position to press the guide surface 3a on the guide rail 3, so that the sliding guide surface 7aa provides a press force onto the guide surface 3a. Also, the sliding guide surface 8a of the guide member 8 is capable of protruding from a retracting position spaced from the guide surface 4a of the guide rail 4 to a press position to press the guide surface 4a on the guide rail 4, so that the sliding guide surface 8a provides a press force onto the guide surface 4a. As the

press members

5 and 6, for example, typically, a hydraulic cylinder can be used. The press member 5 extends the guide member 7 in the directions of the gravitational force and the normal line of the guide surface 3a, and moves the guide surface 3a away from the guide unit 9(and 10) so that the sliding guide surface 7aa of the guide member 7 pushes the guide surface 3a to provide a press force. In the same manner, the press member 6 extends the guide member 8 in the directions of the gravitational force and the normal line of the guide surface 4a, and moves the guide surface 4a away from the guide unit 11(and 12) so that the sliding guide surface 8a of the guide member 8 pushes the guide surface 4a.

On the sliding guide surfaces 7aa and 8aa, a diamond-like carbon (DLC) is coated. For example, a DLC coating layer (DLC membrane) consisting of an amorphous structure whose composition mainly consists of carbon. Moreover, on the sliding guide surfaces 7aa, 8aa made of chrome molybdenum steel, a diffusion layer of nitrogen is formed by a radical nitriding method. A DLC layer can be coated on a layer or membrane of a nitride like nitriding chrome formed on the diffusion layer of nitrogen by PVD sputtering.

Next, hereinafter, the operations of the

guide members

7, 8 and the

press members

5, 6 and the relationship between the guide units 9 to 12 are explained in detail. In the following description, as an example, it is focused on the guide unit 9 in which the guide rail 3 is inserted and its relationship with the guide member 7 is explained with reference to Fig. 2A and 2B. The other guide units 10 to 12 and the guide member 8 are provided in the same manner. Fig. 2A shows a cross section portion 2A-2A of Fig. 1C. Fig. 2A shows the guide unit 9 in a condition where the sliding guide 7aa is in a stowed position. Fig. 2B shows the guide unit 9 in a condition where the sliding guide 7aa is in a press position.

The guide rail 3 is inserted in the guide unit 9. The first side of the guide rail 3 has a first sliding surface 3b that extends along the guide rail 3 and is angled with a constant angle to the guide surface 3a of the guide rail 3, and a second sliding surface 3d that extends along the guide rail 3 and is angled with a constant angle to the first sliding surface 3b. In contrast, the second side surface as the other side has a third sliding surface 3d that extends along the guide rail 3 and is angled with a constant angle to the guide surface 3a of the guide rail 3 and a fourth sliding surface 3e that extends along the guide rail 3 and is angled with a constant angle to the third sliding surface 3c. The first and third sliding

surfaces

3b, 3d are a line symmetry with regard to the normal line of the guide surface 3a, while second and fourth sliding

surfaces

3c, 3e are a line symmetry with regard to the normal line of the guide surface 3a.

In the same manner of the conventional type of the roller guide, a circular groove is internally provided in the guide unit 9. In this embodiment, the

circular grooves

9a, 9b of the guide unit 9 are provided on the first side of the guide rail 3, while the

circular grooves

9c, 9d of the guide unit 9 are provided on the second side of the guide rail 3. The circular groove 9a is provided to be perpendicular to the first sliding surface 3b, while the circular groove 9b is provided to be perpendicular to the second sliding surface 3c. Also, the circular groove 9c is provided to be perpendicular to the third sliding surface 3d, while the circular groove 9d is provided to be perpendicular to the fourth sliding surface 3e.

In each of the

circular grooves

9a, 9b, 9c and 9d of the guide unit 9, similar to the conventional type of the roller guide, plural rolling elements make a line to form a rolling element group so as to slide the guide unit 9 along the guide rail 3. The

circular grooves

9a and 9b have the first rolling element group that rolls over on the first sliding surface 3b and the second rolling element group that rolls over on the second sliding surface 3c, respectively. Similarly, the

circular grooves

9c and 9d have the third rolling element group that rolls over on the third sliding surface 3d and the fourth rolling element group that rolls over on the fourth sliding surface 3e, respectively. The

circular grooves

9a, 9b, 9c and 9d have openings on the side of the guide rail 3 inside the guide unit 9. The rolling

elements

13a, 13b, 13c and 13d (each elements are plural) positioned on the side of the guide rail 3 among the rolling elements of each of the rolling element groups are capable of respectively contacting the first sliding surface 3b, the second sliding surface 3c, the third sliding surface 3d and the fourth sliding surface 3e through the openings and rolling.

In this embodiment, the first sliding surface 3b and the second sliding surface 3c form a recessing surface on the first side of the guide rail 3, while the third sliding surface 3d and the fourth sliding surface 3e form a recessing surface on the second side of the guide rail 3. The rolling elements in the guide unit 9 are preloaded. The preloaded forces to the rolling element 13a and the rolling element 13c have force components in directions to have the rolling element 13a and the rolling element 13c respectively push up the first sliding surface 3b and the third sliding surface 3d. Also, the preloaded forces to the rolling element 13b and the rolling element 13d are balanced with those preloaded forces having force components in a direction to have the rolling element 13b and the rolling element 13d respectively push down the second sliding surface 3c and the fourth sliding surface 3e. The relationship between the guide rail 3 and guide unit 10 and between the guide rail 4 and guide

units

11, 12 are the same.

The guide rails 3 and 4 are under the load of the movable member 2 through the

guide units

9, 10, 11 and 12. The load from the movable member 2 corresponds to the own weight of the movable member 2 and weights on the movable member 2. The load from the movable member 2 is shared by the

guide units

9, 10, 11 and 12. It is divided by the number of the guide units in which guide rails are inserted. In the condition where the press member 5 does not drive and the sliding guide surface 7aa of the guide member 7 does not contact the guide surface 3a of the guide rail 3, shown in Fig. 2A, the following relationships of forces are caused between each of the rolling

elements

13a, 13b, 13c and 13d and each of the first, second, third and

fourth slide surfaces

3b, 3c, 3d and 3e.

The guide unit 9 is pressed onto the guide rail 3 by the shared-load to the guide unit 9 by the load from the movable member 2. Because the second and fourth sliding

surfaces

3c, 3e are under the shared-load to the guide unit 9 through the rolling

elements

13b, 13d, the guide unit 9 is distorted in the direction of the shared-load to the guide unit 9(the downward direction in Fig. 2A). The pre-load from the first and

third surfaces

3b, 3d to the rolling

elements

13a, 13c decreases, while the pre-load from the second and

fourth surfaces

3c, 3e to the rolling

elements

13b, 13d increases. In this way, in consideration of load from the movable member 2, even though the pre-loads to the rolling elements balance in each of the guide units, there occurs unbalance by the load of the movable member 2 as the whole guide units.

In order to dissolve the problem of the unbalance, as shown in Fig. 2B, the press member 5 is operated so that the sliding guide surface 7aa of the guide member 7 contacts the guide surface 3a to press it. In the end, in the guide unit 9, the condition of the load unbalances caused by the load from the movable member 2 between the rolling elements and the first, second, third and fourth sliding

surfaces

3b, 3c, 3d and 3e is dissolved so that the unbalance condition gets back to the balance condition in which the pre-loads from the rolling elements to the first, second, third and fourth sliding

surfaces

3b, 3c, 3d and 3e balance.

In order to dissolve the problem of the unbalance, the press force in which the sliding guide surface 7aa of the guide member 7 contacts and presses the guide surface 3a substantially corresponds to the force in which the load imparted from the movable member 2 to each guide rail, e.g. the guide rail 3, is divided by the number of the press members provided for one guide rail. For example, with reference to the example shown in Fig. 1A, the movable member 2 is supported by the two

guide rails

3, 4. One press member 5 is provided for the guide rail 3. Assuming that the movable member 2 whose weight is M (kg) is supported by two

guide rails

3, 4, the load distributed to one guide rail, e.g. the guide rail 3, is M/2(kg). Therefore, the press force to press the guide surface 3a with the sliding guide surface 7aa of the guide member 7 by driving the press member 5 is equivalent to M/2(kgf). If two press members are assigned for one guide rail, the press force to press the guide surface becomes the half of the press force in the case of one press member. That is, in this case, the press force to press the guide surface is M/4(kgf). In actual case, the load imparted to each guide rail is uneven, the press force(a predetermined press force) to contact and press each guide surface with each sliding guide surface of the press member should be determined in consideration of the condition of the load. In the case where the guide rail 3 is inclined, the force to press the guide surface 3a with the sliding guide surface 7aa of the guide member 7 by the press member 5 corresponds to the load imparted in the direction perpendicular to the guide surface 3a(in the direction of the normal line of the guide surface).

Next, it is explained how to use the guide apparatus 1 of the present invention. In the stand-by condition of the cutting process, when the movable member 2 is moved along the

guide rails

3, 4 to a predetermined position, the movable member 2 is moved without operating the

press members

5, 6 in the condition where the

guide members

7, 8 are stowed.

In the condition under the process, e.g. cutting process, when the movable member 2 is moved, the guide member 7 is operated to protrude the press member 5 to the press position so that the sliding guide surface 7aa of the guide member 7 is pressed onto the guide surface 3a of the guide rail 3. In the end, the guide unit 9 moves along the guide rail 3 while the sliding guide surface 7aa slides on the guide surface 3a, in the condition where the sliding guide 7aa is pressed onto the guide surface 3a with the certain load that does not cause the load unbalance between the press force (the load by both the own weight of the movable member and the preload) loaded onto the first sliding surface 3b from the rolling element 13a of the first rolling element group and the press force (the load by both the own weight of the movable member and the preload) loaded onto the second sliding surface 3c from the rolling element 13b of the second rolling element group.

Similarly, the press member 5 presses the sliding guide surface 7aa onto the guide surface 3a with a load to cause an appropriate friction force in the condition where the press force (the load by both the own weight of the movable member and the preload) loaded onto the third sliding surface 3d from the rolling element 13c of the third rolling element group and the press force (the load by both the own weight of the movable member and the preload) loaded onto the fourth sliding surface 3e from the rolling element 13d of the fourth rolling element group. In this condition, the guide unit 9 moves along the guide rail 3 while the sliding guide surface 7aa slides on the guide surface 3a. The other press member 6 on the side of the guide rail 4 is operated in the same manner as the press member 5. Furthermore, in an actual case, because the center of gravity of the movable member is not necessarily to be located at the center of the movable member 2, the movable member 2 is forced by the torque caused by eccentricity of the center of gravity of the movable member 2. Therefore, it is necessary to adjust the press force with which the press member 5 presses the sliding guide surface 7aa onto the guide surface 3a in consideration of the torque.

The preload condition of the rolling elements is returned to be balanced by pressing the sliding guide surface by the press member so that the difference between coefficients of dynamic and static frictions can be reduced. In addition, it is possible to use the rolling and sliding guides together. In this case, the difference between coefficients of dynamic and static frictions can be smaller than that in the case where only the sliding guide is used. Furthermore, coating a DLC membrane on the sliding surface of the sliding member brings a huge effect to drastically reduce the difference between coefficients of dynamic and static frictions. That is, disadvantage of the sliding guide in which a low machining accuracy is caused by great difference between coefficients of dynamic and static frictions can be compensated by a hybrid guide in which a rolling guide and a sliding guide with DLC coating are combined so that the difference between coefficients of dynamic and static frictions is reduced to improve the machining accuracy. Furthermore, the disadvantage of the rolling guide that tends to cause vibration can be redeemed by a hybrid guide. Especially, in the case of the circular cutting process, machining with a high circularity can be achieved.

In this embodiment, as above, it is explained that two

guide units

9 and 10 are arranged with regard to one guide rail 3 and the press member 5 is positioned between the

guide units

9 and 10. However, the combination between one guide unit 9 and the press member 5 brings the same effect. On the contrary, it is possible to provide the plural guide units more than two on one guide rails.

Second Embodiment

Next, with reference to the Fig. 3A and 3B, a hybrid guide apparatus as the second embodiment is explained. Fig. 3A shows a perspective view of a hybrid guide apparatus as the second embodiment. Fig. 3B shows a cross section view of a hybrid guide apparatus as the second embodiment in a view of the direction perpendicular to the longitudinal direction of the guide rail. In the second embodiment, the guide apparatus 1 includes the

guide rails

3, 4 and the guide units 9 to 12. The second embodiment, however, is different from the first embodiment in the point where the

guide rails

3 and 4 are arranged to extend in a vertical direction to the base of the guide apparatus 1. The guide rail 3 into which the

guide units

9, 10 are inserted is vertically arranged, while the guide rail 4 into which the

guide units

11, 12 are inserted is vertically arranged. In the following description, the different points from the first embodiment are explained.

In the second embodiment, because the center of gravity of the movable member 2 is displaced from the

guide rails

3, 4, once the movable member 2 is arranged on the

guide rails

3, 4 to slide along them in a vertical direction, a torque is caused around the virtual rotation center A by the load in a downward direction of the movable member 2. The virtual rotation center A is located substantially at a middle point on a virtual line connected between the centers of the fixed portions of the

guide units

9, 10 on the guide rail 3. The force F imparted from the guide rail 3 to the guide unit 9 on the upper side among the

guide units

9, 10 on the guide trail 3 is directed in opposition to and has the same magnitude as the force F imparted to the guide unit 10 on the lower side among the

guide units

9, 10 on the guide rail 3. For example, as shown in Fig. 2A, in the cross section of the guide rail 3 and the guide unit 9, the fixed portion of the guide unit 9 on the guide rail 3 implies substantially a middle point between the contact point at which the rolling elements 13a among the first rolling elements groups contact the first sliding surface 3b and the contact point at which the rolling elements 13b among the second rolling elements group contact the second sliding surface 3c.

In detail view of the inside of the guide unit 9 of the second embodiment, there is a difference between the press forces imparted from the rolling elements to the sliding surface in the guide unit. In the second embodiment, in the same manner as the first embodiment, the rolling

elements

13a, 13b, 13c and 13d positioned on the side of the guide rail 3 are arranged to contact the first, second, third and

fourth surfaces

3b, 3c, 3d and 3e in the condition where the preload to press the first, second, third and

fourth surfaces

3b, 3c, 3d and 3e is imparted. In consideration of Fig. 2A as the second embodiment, the load is directed in opposition to that of the first embodiment. That is, the load W₁ consisting of the own weight of the movable member 2 and the weight of the machine members on the movable member 2 cause a torque around the virtual rotation axis A down the movable member 2 to pull the guide unit 9 on the upper side from the guide rail 3 and push the guide unit 10 on the lower side onto the guide rail 3. Assuming that the distance from the load center of the weight W₁ to the virtual rotation axis center A is defined as R₁, the magnitude of the torque is represented by (W₁)x(R₁). The torque (W₁)x(R₁) causes the guide unit 9 to displace the guide unit 9 from the guide rail 3 with the force F. On the other hand, the torque (W₁)x(R₁) causes the guide unit 10 to push the guide unit 9 onto the guide rail 3 with the opposite force F. In the guide unit 9, the preload to the rolling

elements

13a, 13c increases, while the preload to the rolling

elements

13b, 13d decreases. That is, in this case, this is because the rolling

elements

13a, 13c are more pressed onto the fist and the third sliding

surfaces

3b, 3d when the guide unit 9 is forced to be displaced from the guide rail 3. In contrast, in the guide unit 10, the preload to the rolling

elements

13a, 13c decreases, while the preload to the rolling

elements

13b, 13d increases. That is, in this case, this is because the rolling

elements

13b, 13d are more pressed onto the second and the fourth sliding

surfaces

3c, 3e when the guide unit 10 is forced to be pressed onto the guide rail 3. The relationships of these loads can be applied into the guide rail 4. That is, the guide unit 11 on the upper side in the vertical direction corresponds to the guide unit 9, while the guide unit 12 on the lower side in the vertical direction corresponds to the guide unit 10. In this manner, the torque caused by the load of the movable member 2 in the vertical direction comes into being unbalances of the loads inside the guide units 9 to 12.

In order to solve the problem of the unbalance condition, in the second embodiment, the two press members that are explained in the first embodiment are provided between the

guide units

9, 10 into which the guide rail 3 is inserted. That is, between the

guide units

9, 10, the first press member 5a is provided on the upper side in the vertical direction and the second press member 5b is provided between the first press member 5a and the guide unit 10 on the lower side in the vertical direction. The first press member 5a is capable of protruding the first guide member 7a having the first sliding guide surface 7aa from the stowed position away from the guide surface 3a of the guide rail 3 to the press position to press the guide surface 3a, so that the first sliding guide surface 7aa can be pressed onto the guide surface 3a. The second press member 5b is capable of protruding the second guide member 7b having the second sliding guide surface 7ba from the stowed position away from the guide surface 3a of the guide rail 3 to the press position to press the guide surface 3a, so that the second sliding guide surface 7ba can be pressed onto the guide surface 3a. In the same way, on the side of the guide rail 4, two press members are also provided.

The first and

second press members

5a, 5b press the first and second sliding guide surfaces 7aa, 7ba onto the guide surface 3a on the guide rail 3 so that the press force loaded onto the slide surface from the rolling elements group to the guide unit 9 as the first guide unit and the press force loaded onto the slide surface from the rolling elements group to the guide unit 10 as the second guide unit are balanced. In this condition, the

guide units

9, 10 are slidable along the guide rail 3 while sliding the first and second sliding guide surfaces 7aa, 7ba on the guide surface 3a. This can be applied to the

guide units

11, 12 on the guide rail 4 on the other side of the guide rail 3 in the same manner as the above. In the same manner as the first embodiment, the process to coat a DLC layer on the first and second sliding guide surfaces 7aa, 7ba of the first and

second guide members

7a, 7b and the other sliding guide surfaces of the guide units on the guide rails is performed.

The press force fa of the first press member 5a(first press force) and the press force fb of the second press member 5b(second press force) are set as follows. First, in order to make the torque (W₁)x(R₁) around the virtual rotation center A and the torque in the opposite direction balance, fa and fb are set based on the following equation(1).

W₁ x R₁ + fa x ra₁ = fb x ra₂ (1)

For example, first, without considering, with neglecting, the press force fa of the first press member 5a, the press force fb of the second press member 5b is determined to satisfy the equation(1). And then, in order to obtain the appropriate sliding under the condition of the press force fb based on the equation(1), the press force fa of the first press member 5a is determined by the friction coefficient between the first sliding guide surface 7aa and the guide surface 3a of the guide rail, and so on. In general, although ra₁ and ra₂can be determined as different distances, it may be determined as a common distance. The appropriate distance can be determined by the balance between torques caused by the set press forces fa, fb and the torque caused by the W₁.

Third Embodiment

Next, with reference to the Fig. 4, a hybrid guide apparatus as the third embodiment is explained. In the hybrid guide apparatus as the third embodiment, in addition to the guide rail extending in the vertical direction in the second embodiment, other guide rails is equipped. That is, the guide rails 13, 14 are provided on the base 12 so that the guide rails 13, 14 extend in the direction perpendicular to the direction along the

guide rails

3 and 4. The guide rails 13, 14 are respectively inserted into the

guide units

15, 16. Also, although it is not shown in this drawing, guide units other than the

guide units

15, 16 are provided with even spaces on the guide rails 13, 14 so that the base 12 is capable of smoothly sliding on the guide rails 13, 14.

Between the guide units into which the guide rail 13 is inserted, the third press member 17 is provided so that the sliding surface of the third press member 17 is capable of pressing the guide surface of the guide rail. Similarly, between the guide units into which the guide rail 14 is inserted, the fourth press member 18 is provided so that the sliding surface of the fourth press member 18 is capable of pressing the guide surface of the guide rail. The guide unit 15 on the upper side and the guide unit 16 on the lower side are impinged with the torque around the virtual rotation center B by the load of the total weight W₂ including the weights of the base 12 and the

guide rails

3, 4 in addition to the weight W₁ of the movement member 2. Assuming that the distance from the center of the cross section of the guide rail 13 and the center of the cross section of the guide rail 14 to the center of the gravity of the total weight W₂ including the weights of the base 12, the

guide rails

3, 4 and the guide units 9 to 12 is defined as R₂, the torque around the virtual rotation center B is (W₂)x(R₂). Therefore, in the same manner as the second embodiment, in order to balance the torques around the virtual rotation center B, the press forces fc, fd in which the sliding surfaces of the third press member 17 and the fourth press member 18 press the guide surfaces of the guide rails 13, 14 are set as follows.

First, with regard to the torque (W₂)x(R₂) around the virtual rotation center B, the press forces fc, fd are set to balance the torques that are respectively impinged in opposite directions, based on the following formula (2).

W₂xR₂ + fc x rb₁ = fd x rb₂(2)

For example, first, without considering, with neglecting, the press force fc of the third press member 17, the press force fd of the fourth press member 18 is determined to satisfy the equation(2). And then, in order to obtain appropriate sliding under the condition of the press force fd based on the equation(2), the press force fc of the third press member 17 is determined by the friction coefficient between the sliding guide surface of the third press member 17 and the guide surface of the guide rail 13, and so on. In general, although rb₁ and rb₂can be determined as different distances, it may be determined as a common distance. The appropriate distance can be determined by the balance between torques caused by the set press forces fc, fd and the torque caused by the W₂. In the same manner as the first embodiment, the process to coat a DLC layer on the sliding guide surfaces of the third press member 17 and the fourth press member 18 is performed.

In the actual application for the three-dimensional machine tools, the first, second and third embodiments can be combined. That is, the first, second and third embodiments can be respectively applied for the movements in horizontal axis on a horizontal surface, in vertical axis on the vertical surface and in horizontal axis on the vertical surface according to the purpose of machine tools.

For example, as shown in Figs. 7A to 7F, in addition to the first, second and third embodiments, there are variations of the combinations of the first, second and third embodiments. In all of these embodiments, the press members and the guide members having the sliding guide surfaces are provided in the same manner as those of the first, second and third embodiments.

The embodiment shown in Fig. 7A is modified from the first embodiment. The first guide rail 3 is horizontally provided with a different height from that of the second guide rail 4. The heights of the

guide rails

3 and 4 can be arbitrarily determined according to the purpose of a device in machine tools. The first and

second guide rails

3, 4 are inserted into the

guide units

9 and 11 with other guide units 10 an 12(not shown). The movable member 2 is supported by the guide units 9 to 12.

In the embodiment of Fig. 7B, the guide rail 3 and the guide rail 4 (not shown) are inclined with an angle "alpha" to the horizontal surface. The angle "alpha" can be arbitrarily determined according to the purpose of a device in machine tools. The guide units 9 to 12 and the movable member are provided in the same manner as those of the first embodiment.

In Figs. 7C and 7D, the first and third embodiments are combined. That is, in Fig. 7C, the guide rail 33 and the other guide rail (not shown) in parallel to the guide rail 33 are horizontally in the manner of the first embodiment. The other guide rails (one is the guide rail 3 and the other one is the guide rail(not shown) in parallel to the guide rail 3 are vertically provided. The

other guide rails

13 and 14 are provided in perpendicular to both the couple of the guide rails including the guide rail 33 and the couple of the guide rails including the guide rail 3. The

movable members

22, 2 and 12 are respectively movable along the guide rails by the

guide units

39, 40, 9, 10, 15 and 16 in which the above guide rails are inserted. In the embodiment of Fig. 7D, the direction of the guide rails 33 and 34 are modified by providing those guide rails in perpendicular to the direction in the case of the embodiment of Fig. 7C in the same plane.

In Fig. 7E, the first and second embodiments are combined into the embodiment shown in Fig. 7A. That is, the movable member 43, the

guide units

39, 40 and the guide rail 33 with the other guide rail (not shown) are arranged in the manner of the first embodiment on the movable member 2 provided in the manner of the embodiment shown in Fig. 7A. The movable member 47, the

guide units

44 and 45, the guide rail 46 are provided in the same manner.

Fig. 7F shows the combinations of the first embodiment and the embodiment shown in Fig. 7A as a machining center. Those embodiments can be easily combined according to the purpose of machine tools. The tool head 49 are provided on the movable member 42 with the

guide units

39, 40 and the guide rail 33 in the embodiment in Fig. 7A. The

other guide rails

3, 4 are provided in perpendicular to the guide rail 33 to move the movable member 42 in the direction along the axis of the main spindle 48.

The meritorious effect of the present invention can be understood from the test result shown in Table 1. This test is performed by the hybrid type of three-dimensional guide apparatus into which the first, second and third embodiments are combined and non-hybrid type of guide apparatus. The test result shows the comparison of the displacement variation of the vibrations in the movement of the tool table as the movable member. The face mill cutter is used as the tool. The displacement variation was measured at the upper, middle and lower portions in the vertical axis by the vibration meter (VIBRATION METER MODEL VM 1970). As shown in Table 1, at the upper and middle portions, especially, the big difference can be observed. That is, the displacement variations in the case of the non-hybrid types of the guide apparatus (examples 1 and 2) indicate about twice of that in the case of the hybrid types of the guide apparatus (examples 1 to 4). It is understood that the meritorious effects of the present invention come out in the case of the large gravity effect.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2009-249915, filed on October 30, 2009, which is hereby incorporated by reference herein in its entirety.

Claims

A guide apparatus for a machine tool, comprising:
a guide unit that supports a movable member;
a guide rail which is inserted into said guide unit, said guide rail having a guide surface extending along said guide rail;
press member that projects from a retracting position spaced from the guide surface to a press position to press the guide surface, said press member having a sliding guide surface that is capable of pressing the guide surface with regard to the movable member;
wherein said guide unit includes a line group of bearing members to slide said guide unit along the guide rail;
wherein said press member presses the guide surface with the sliding guide surface with a predetermined pressing force and the sliding surface of the said press member slides on the guide surface so that the guide unit is slidable along the guide rail.
A guide apparatus for a machine tool, according to Claim 1, wherein said sliding guide surface is coated with a DLC membrane.
A guide apparatus for a machine tool, according to Claim 1 or 2, wherein the predetermined pressing force has a force component in a direction of a gravitational force, wherein the force component corresponds to a load that is distributed to the guide rail in the direction of a gravitational force.
A guide apparatus for a machine tool, according to any one of Claims 1 to 3, further comprising another guide unit to support and slide the movable member,
wherein said another guide unit includes a line group of bearing members to slide along the guide rail, and
wherein said press member is placed between the guide unit and said another guide unit.
A guide apparatus for a machine tool, according to Claims 1 to 4, wherein said guide rail is placed to extend in a horizontal direction.
A guide apparatus for a machine tool, according to Claims 1 to 4, wherein said guide rail is placed to be inclined with regard to the vertical direction.
A guide apparatus for a machine tool, according to Claims 1 to 4, wherein said guide rail is placed to extend in a vertical direction.
A guide apparatus for a machine tool, comprising:
a first guide unit that supports a movable member;
a second guide unit that supports the movable member of said first guide unit under said first guide unit;
a guide rail that is inserted into said first guide unit and second guide unit, said guide rail having a guide surface extending along said guide rail;
a first press member that projects from a position displaced from the guide surface to a position to press the guide surface, said first press member having a first sliding guide surface that is capable of pressing the guide surface with regard to the movable member;
a second press member that projects from a position displaced from the guide surface to a position to press the guide surface, said second press member having a second sliding guide surface that is capable of pressing the guide surface with regard to the movable member;
wherein each of said first and second guide units includes a line group of bearing members to slide said first and second guide units along the guide rail;
wherein said first press member presses the guide surface with the first sliding guide surface with a first pressing force and said second press member presses the guide surface with the second sliding guide surface with a second pressing force, and the first and second sliding surfaces of the said first and second press members slide on the guide surface so that the first and second guide units are slidable along the guide rail.
A guide apparatus for a machine tool, according to Claim 8, wherein said first and second sliding guide surfaces are coated with a DLC membrane.
A guide apparatus for a machine tool, according to Claims 8 or 9, wherein said first and second guide rails are placed to be inclined with regard to the vertical direction.
A guide apparatus for a machine tool, according to any one of Claims 8 to 10, wherein said first and second guide rails are placed to extend in a vertical direction.
A machine tool including a guide apparatus according to Claims 1 to 11.