Ball screw integrated linear guide unit

A ball screw integrated linear guide unit arranging on an inner end surface of an end cap not only linear guide ball lubricating grease feed passages reaching the curved passages from the grease nipple and a ball screw ball lubricating grease feed passage reaching the ball screw spiral groove from the grease nipple, whereby simultaneous lubrication for linear guide feed line and ball screw feed line can be achieved.

BACKGROUND OF THE INVENTION 
The invention relates to ball screw integrated linear guide units 
preferably used while incorporated into, for example, operating arms of 
robots and X-Y tables. More particularly, the invention is directed to a 
ball screw integrated linear guide unit whose maintenance and durability 
are improved by achieving simultaneous lubrication for both a ball screw 
feed line and a linear guide feed line. 
A conventional grease supplying structure for a single linear guide unit is 
disclosed, for example, in Japanese Utility Model Examined Publication No. 
63-29940. This conventional example includes: an axially extending guide 
rail having ball rolling grooves on lateral sides thereof; and a slider 
stretched over the guide rail, the slider being U-shaped and having ball 
rolling grooves on both inner side surfaces thereof so as to confront the 
ball rolling grooves of the guide rail. A large number of balls are 
interposed between the confronting ball rolling grooves of the guide rail 
and the slider. The slider is axially movable by the rolling of the balls 
while guided by the guide rail. End caps are mounted on both front and 
rear end surfaces of the slider, respectively. Each end cap has a 
circulating passage for effecting endless circulation by causing the balls 
to return therethrough. The circulation passage includes semicircular 
recessed spaces formed on each end cap and semi-cylindrical return guides, 
each having arcuate outer circumference corresponding to the semi-circular 
curved surface of the recessed space. By attaching the return guide on the 
semi-circular recessed space orthogonally, the circulation passage becomes 
semi-doughnut-shaped. 
As a result of such a construction, the recessed portion on the flat 
surface side of each semi-cylindrical return guide is used as a 
lubricating groove, and a lubricating hole opened from the lubricating 
groove toward the semi-doughnut-shaped circulation passage is formed by 
cutting through the side surface of the return guide. On the other hand, a 
grease feed groove is formed on an end surface of each end cap while 
communicated with the lubricating grooves of the return guide from a 
grease nipple mounting hole. The end caps are mounted on the end surfaces 
of the slider, and then the grease nipple is attached to the slider. 
Grease supplied from the grease nipple reaches the lubricating grooves of 
the return guides via the grease feed groove to lubricate the rolling 
balls. 
However, the lubricating structure for the conventional example is designed 
to lubricate the balls of an independent linear guide unit. Therefore, if 
this lubricating structure is directly applied to a ball screw integrated 
linear guide unit in which a linear guide unit and a ball screw unit are 
integrated with each other, the balls for the linear guide can be 
lubricated, but the balls for the ball screw cannot be lubricated. Hence, 
in the case of the ball screw integrated linear guide unit, the ball screw 
balls cannot be lubricated by the grease supplied from the grease nipple; 
but the only means for greasing them is by loading grease within the ball 
screw nut in advance. Thus, the unit has to be disassembled periodically 
to replenish the lubricant. 
The object of the invention is therefore to overcome the above problems by 
providing a ball screw integrated liner guide unit in which a lubricating 
structure applicable to lubricating balls in both a linear guide feed line 
and a ball screw feed line is arranged in a ball screw nut. 
SUMMARY OF THE INVENTION 
To achieve the above object, the invention is applied to a ball screw 
integrated linear guide unit which includes: a guide rail with axially 
extending ball rolling grooves on lateral surfaces thereof; a ball screw 
shaft being arranged in parallel with the guide rail and having a spiral 
groove around the outer surface thereof; and a ball screw nut having a 
spiral groove confronting the spiral groove of the ball screw shaft and 
being screwed into the ball screw shaft through a large number of balls 
rolling within both the spiral grooves confronting each other; wherein 
ball rolling grooves confronting the ball rolling grooves of the guide 
rail are formed on both lateral surfaces of the ball screw nut; axially 
extending ball return passages being cut through the nut in parallel with 
the ball rolling grooves; end caps are fixed on both front and rear end 
surfaces of the ball screw nut; curved passages for communicating the ball 
rolling grooves and the ball return passages corresponding to the ball 
rolling grooves are formed on end surfaces of each end cap; a large number 
of linear guide balls are rotatably interposed within a circulating 
passage including both the confronting ball rolling grooves, the curved 
passages, and the ball return passages; and the ball screw nut is axially 
movable with respect to the guide rail through circulation of the large 
number of linear guide balls. In such a ball screw integrated linear guide 
unit, a lubricating grease supplying mechanism for simultaneously 
supplying a lubricating grease into the curved passages and the ball screw 
spiral groove are provided. 
The lubricating grease supplying mechanism may be provided in such a manner 
that a grease nipple is attached to the end cap, and both linear guide 
ball lubricating grease feed passages reaching the curved passages from 
the grease nipple and a ball screw ball lubricating grease feed passage 
reaching the ball screw spiral groove from the grease nipple are provided 
on an inner end surface of each end cap. 
In the invention both the grease feed passages for the linear guide balls 
extending from the grease nipple to the linear guide curved passages and 
the grease feed passage for the ball screw balls extending from the grease 
nipple to the spiral groove of the ball screw nut are arranged on the 
inner end surface of each end cap. Therefore, the lubricant charged to the 
grease nipple can be supplied to both lubricating lines, i.e., the linear 
guide and the ball screw lines, simultaneously. 
This feature contributes to significant improvement of the maintenance and 
durability and permits long operation without disassembling the unit.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
An embodiment of the invention will now be described with reference to the 
appended drawings. 
As shown in FIGS. 1 and 2, a guide rail 1 of this embodiment is 
substantially U-shaped in horizontal section and has ball rolling grooves 
2 formed on the inner sides of lateral surfaces 1a, 1a rising from a 
bottom thereof, respectively. These ball rolling grooves 2 extend in an 
axial direction while confronting each other. Bearing plates 3, 4 are 
screwed on both axial ends of the guide rail 1. A ball bearing, although 
not shown, is mounted on the bearing plate 3, whereas not shown angular 
ball bearings are doubly mounted on the bearing plate 4 through a bearing 
housing 6 to form a support unit. A ball screw shaft 7 runs in parallel 
with the ball rolling grooves 2 in the widthwise center of the guide rail 
1. A spiral groove 8 is formed around the ball screw shaft 7 as a ball 
screw groove. One end portion 7a of the ball screw shaft 7 is projected 
outward from the bearing housing 6 so that the shaft can be coupled with 
an output shaft of a not shown drive motor. 
Reference numeral 10 designates a ball screw nut screwed into the ball 
screw shaft 7. The ball screw nut 10 has a square nut body 10A and end 
caps 12 that are secured to both axial ends of the nut body 10A by bolts. 
Around the inner surface of a screw hole formed in the center of the nut 
body 10A is a ball screw groove 9, which is also spiral so as to 
correspond to the ball screw groove 8 on the ball screw shaft 7. The width 
of the nut body 10A is slightly smaller than that of an inner distance 
between both lateral surfaces 1a, 1a of the guide rail 1. In the lower 
opposite lateral surfaces (right and left) of the nut body 10A, ball 
rolling grooves 13, which confront the ball rolling grooves 2 of the guide 
rail 1, respectively, are provided. Linear through holes serving as ball 
return passages 14 are formed by cutting through the nut body 10A in 
parallel with the ball rolling grooves 13. On the other hand, as shown in 
FIGS. 3 to 5, a shaft hole 11 for allowing the ball screw shaft 7 to be 
inserted therethrough is formed in the center of the respective end caps 
12. Semi-doughnut-like curved passages 15 for communicating the ball 
rolling grooves 13 with the ball return passages 14 are formed on the end 
surfaces 12a to be jointed with the nut body 10A. Referring to the 
semi-doughnut-like construction of the curved passages 15, laterally 
projecting portions 17 engageable with the ball rolling grooves 2 of the 
guide rail 1 are formed on the lateral surfaces of the end caps 12, 
respectively. A semicircular recess 18 of a large diameter extends from 
the end surface of each projecting portion 17 to the end surface 12a to be 
jointed with the nut body 10A of each end cap 12. Further, at the center 
of the opening of the semicircular recess 18 is a semi-cylindrical recess 
19 of a small diameter formed so as to be orthogonal to the opening of the 
semicircular recess 18. Each semi-doughnut-like curved passage 15 is 
formed by engaging a semi-cylindrical return guide 20 with the 
semi-cylindrical recess 19. As described above, an endless ball 
circulating passage dedicated to the linear guide is formed, the passage 
including the ball rolling grooves 2 of the guide rail 1, the ball rolling 
grooves 13 confronting the ball rolling grooves 2, the ball return 
passages 14, and the curved passages 15 as shown in FIG. 2. A large number 
of linear guide balls 21 are provided so as to roll inside the endless 
ball circulating passage. Pickup projections 22 for smoothly guiding the 
linear guide balls 21 to the curved passages 15 by picking them up from 
the ball rolling grooves 2 of the guide rail are formed on ends of the 
curved passages of the projecting portions 17 on the lateral surfaces of 
each end cap 12. 
Further, a U-shaped ball circulating passage 24 is incorporated into the 
top of the nut-body 10A as a ball screw ball circulating passage for 
circulating balls 23 of the ball screw which roll within the ball screw 
groove 8 of the ball screw shaft 7 and within the ball screw groove 9 on 
the inner surface of the nut confronting the groove 8. The endless 
circulating system is of a known passage type circulating structure in 
which the balls 23 are picked up by the ball circulating passage 24 from 
the ball screw groove 8, obliquely surpasses a land portion of the ball 
screw shaft 7 along the passage, and returns to the ball screw groove 8. 
The construction of a lubricant feeding system of the embodiment will be 
described with reference to FIG. 3. 
An axially extending recessed groove is formed on the flat side of each 
semi-cylindrical return passage 20. The recessed groove serves as a 
lubricating groove 26. Lubricating holes 27 that are opened toward the 
semi-doughnut-like curved passage 15 are formed by passing through the 
barrel of the return guide 20 from the lubricating groove 26. 
On the other hand, a grease reservoir 30 is provided on the top of the end 
cap 12, and grease nipple attaching holes 31 communicating with the grease 
reservoir 30 are formed to be open on the lateral surfaces. The grease 
nipple attaching holes 31 are prepared on opposite lateral surfaces, right 
and left, as blind holes in advance. When the unit is put in operation, a 
selected one of the blind holes is made to communicate with the grease 
reservoir 30 by cutting through the bottom of the blind hole. A grease 
nipple 32 is thereafter attached to the mounting hole 31. 
On an inner end surface (an end surface contacting the nut body 10A) of 
each end cap 12 are grease feed passages 33 reaching the lubricating 
grooves 26 of the return guides 20 while bifurcated from the grease 
reservoir 30 that is located at the top center of the end cap 12. As a 
result of this construction is a grease feed passage for the linear guide 
formed for supplying the grease from the grease nipple 32 attached to the 
grease nipple attaching hole 31 to the curved passages 15 via the grease 
reservoir 30, the grease feed passages 33, the return guide lubricating 
grooves 26, and the lubricating holes 27. 
Further, on the end surface 12a of the end cap 12 is a feed passage 35 
additionally provided as a grease feed passage for the ball screw. This 
grease feed passage 35 runs from the grease reservoir 30 to the shaft hole 
11 at the center. This grease feed passage 35 is short. For adjusting the 
flow of lubricant in this passage 35 with respect to that in the linear 
guide grease feed passage that is long, the sectional area of this passage 
35 is made smaller than that of the linear guide grease feed passage. 
The operation will be described next. 
Grease as a lubricant is supplied from the grease nipple 32 attached to the 
grease nipple attaching hole 31. The grease loaded to the grease reservoir 
30 reaches the lubricating grooves 26 of the return guides 20 on both 
sides via the right and left grease feed passages 33, and supplied to the 
curved passages 15 past the lubricating holes 27 to thereby lubricate the 
linear guide balls 21 rolling within the curved passages 15. 
At the same time, the grease in the grease reservoir 30 reaches the shaft 
hole 11 via the grease feed passage 35, so that the grease is supplied to 
the ball screw groove 8 of the ball screw shaft 7 to thereby lubricate the 
balls 23 of the ball screw rolling within that groove 8. 
As the ball screw shaft 7 is rotated forward (or reversely) by driving a 
not shown drive motor, the rotation of the shaft is transmitted to the 
ball screw nut 10 through the balls 23 of the ball screw interposed 
between the ball screw groove 8 of the ball screw shaft 7 and the ball 
screw groove 9 of the ball screw nut 10, thereby advancing (or retracting) 
the ball screw nut 10 in the axial direction in response thereto. The 
rotation of the ball screw nut 10 is stopped by the linear guide balls 21 
interposed between the ball rolling grooves 13 of the nut 10 and the ball 
rolling grooves 2 of the guide rail 1. The linear guide balls 21 and the 
ball screw balls 23 circulate through the respective endless circulating 
passages while rolling and moving in association with the movement of the 
ball screw nut 10. During the circulation, the linear guide balls 21 are 
lubricated by supplying the grease in the grease reservoir 30 to the 
curved passages 15 through the grease feed passages 33. 
Similarly, the ball screw balls 23 are lubricated by supplying the grease 
in the grease reservoir 30 to the ball screw groove 8 of the ball screw 
shaft 7 through the grease feed passage 35. 
The grease can be replenished only by supplying the grease from the grease 
nipple 32 with a grease gun, contributing to easy handling by the user. 
As a result of the above operation, greasing can be effected on both the 
linear guide and the ball screw lines of the ball screw integrated linear 
guide unit collectively at once, which contributes to easy maintenance and 
significant improvement of durability. 
While an example of a single-line-per-single-side endless ball circulating 
passage for the linear guide has been described in the above embodiment, a 
multi-line structure is also applicable. 
As described in the foregoing, the ball screw integrated linear guide unit 
of the invention is designed to arrange, on the inner end surface of each 
end cap, the grease feed passages for the linear guide balls which 
communicate with the curved passages of the linear guide from the grease 
nipple and the grease feed passage for the ball screw balls which 
communicates with the spiral groove of the ball screw nut from the grease 
nipple. Therefore, the grease can be replenished to the two feed lines, 
i.e., the linear guide and the ball screw feed lines, simultaneously by 
supplying grease from the grease nipple. As a result, the advantages such 
as remarkable improvement of maintenance and durability as well as long, 
stable operation without disassembling the unit can be obtained. 
The foregoing description of preferred embodiments of the invention has 
been presented for purposes of illustration and description. It is not 
intended to be exhaustive or to limit the invention to the precise form 
disclosed, and modifications and variations are possible in light of the 
above teachings or may be acquired from practice of the invention. The 
embodiments were chosen and described in order to explain the principles 
of the invention and its practical application to enable one skilled in 
the art to utilize the invention in various embodiments and with various 
modifications as are suited to the particular use contemplated.