JP3525650B2 - Static pressure feed screw device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a double nut type static pressure feed screw device used for moving a moving body such as a grindstone head. 2. Description of the Related Art Conventionally, a feed screw device using a ball screw has been used as a feed screw device for moving a grindstone table of a grinding machine. However, in the feed screw device using such a ball screw, there are the following problems in order to move the grindstone head at high speed. That is, in order to move at high speed, it is necessary to enlarge the lead of the feed screw. However, increasing the size of the lead substantially reduces the number of balls that support the screw. For this reason, the rigidity of the nut screwed with the feed screw decreases, and high-speed movement becomes impossible. In order to solve such a conventional problem, the inventor of the present application attempted to use a hydrostatic feed screw for a feed screw device of a grinding wheel head. Conventional static pressure feed screw devices include the following. That is, in the static pressure feed screw device disclosed in Japanese Patent Application Laid-Open No. 60-78153, groove-shaped static pressure pockets divided in the circumferential direction are arranged at both ends of the female screw. It is one in which groove-shaped static pressure pockets that are spirally continuous are arranged. With such a configuration,
This static pressure feed screw device secures rigidity in the radial direction and the thrust direction by divided static pressure pockets at both ends, and secures rigidity in the thrust direction by the spirally continuous static pressure pockets. I have. [0004] In the above-described hydrostatic feed screw device, rigidity in the radial direction is ensured by the hydrostatic pockets divided at both ends. However, since the static pressure pocket is formed on the inclined side surface of the female screw, the static pressure of the static pressure pocket is not a component in the radial direction, and the flank of the feed screw has a large inclination. Acts as a thrust force. Therefore, in the above-described static pressure feed screw device, the radial centering action is small, and sufficient rigidity in the radial direction cannot be obtained. Regarding the rigidity in the thrust direction,
Part of the static pressure is taken in the radial direction. In addition, in the spirally continuous static pressure pocket, a radial component in which the centering action does not work occurs. As a solution to such a problem, there is a static pressure feed screw device as shown in FIG. This is the feed screw 51
In addition to the thrust static pressure pocket 53, a radial bearing 52 having a radial static pressure pocket is provided at both ends of a nut 50 screwed into the nut. This radial bearing 5
Reference numeral 2 directly supports the upper surface portion of the male screw convex portion 51a of the feed screw 51, so that all of the static pressure acts in the radial direction, and has an effect that the rigidity in the radial direction is high. However, with such a configuration, the size of the nut 50 is equal to the sum of the outer diameter a of the feed screw 51 and the thickness b of the radial bearing 52. Therefore, there is a problem that the size is larger than that of the conventional hydrostatic feed screw device. The problem of such an increase in the diameter is caused by increasing the tooth length c of the feed screw 51 so that the feed screw 51 can move at a high speed, increasing the static pressure receiving area and increasing the rigidity in the thrust direction. , Will be more noticeable. In addition, it is extremely difficult in processing to integrally form a static pressure pocket on the lower surface of the female screw concave portion of the nut 50 so as to face the upper surface of the male screw convex portion 51a of the feed screw 51. For this reason, in this hydrostatic feed screw device, the radial bearing 52 is configured to be assembled to the nut 50 as a separate member. Thus, the radial bearing 52
The use of a separate member increases the number of assembly steps and increases the cost. Furthermore, since the radial bearing 52 is a separate member, the radial bearing 52 cannot be attached to the portion where the thrust static pressure pocket 53 is provided. For this reason, there is a problem that the length of the nut 50 becomes longer than necessary. Accordingly, it is an object of the present invention to provide a low-cost static pressure feed screw device which can secure sufficient rigidity in both the radial direction and the thrust direction, can be operated at high speed, and can be reduced in size. SUMMARY OF THE INVENTION The present invention has been made to achieve the above-mentioned object, and includes a pair of adjacent nuts attached to a moving body and a feed screw screwed to the nuts. In a double-nut type static pressure feed screw device provided with a static pressure pocket in which hydraulic oil is supplied to a threaded portion of the pair of nuts, a bolt is attached to the moving body at one end of each of the pair of nuts that does not face each other. Forming a flange portion for passing the bolt through each of the flange portions so that the phase of the pair of nuts can be varied in the circumferential direction.
In order to apply a static pressure only in the thrust direction, a long slot is formed in the side face of the female screw of the pair of nuts on the side facing the respective flanges in a spiral shape. A continuous groove-shaped static pressure pocket is formed, and furthermore, a plurality of groove-shaped grooves are equally divided on an upper surface portion parallel to the axial direction of the convex portion of the female screw of the pair of nuts to apply a static pressure only in the radial direction. In which a radial static pressure pocket is formed. An embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a grindstone head (moving body) 1 having a hydrostatic feed screw device of the present embodiment. This wheel head 1
This is for grinding a workpiece W, which is a camshaft rotatably supported by support means (not shown). The grinding wheel base 1 is provided on a guide surface 60a provided on a base 60 as shown in FIG.
Are slidably supported so as to be movable only in the left-right direction. A grinding wheel 61 for grinding a workpiece W is rotatably supported at the tip of the grinding wheel table 1. The grinding wheel 61 is provided with a servo motor 6 (not shown) provided coaxially.
2 is driven to rotate. The grindstone head 1 has a cylindrical space 1a in which the feed screw 6 relatively advances and retreats from the rear end of the grindstone head 1 toward the inside. A static pressure feed screw device 70 described later is attached to the end of the space 1a. The static pressure feed screw device 70 mainly includes a pair of nuts 4 and a feed screw 6. At the end of the base 60, there is provided a connecting portion 66 to which a servomotor 63 for driving the feed screw 6 is rotated. A ball bearing 64 that rotatably supports the end of the feed screw 6 is attached to one end of the connection portion 66, and a servomotor 63 is attached to the other end. And both of these
It is connected by a coupling 65 in the connection portion 66. Next, the static pressure feed screw device 70 will be described with reference to FIGS. 2 and 3 show cross sections of the hydrostatic feed screw device 70 in different phases. 2 shows the inner wall surface of the nut 4 without the feed screw 6, and FIG.
The inner wall surface of the nut 4 is shown. In the static pressure feed screw device 70 of the present embodiment, a pair of nuts 4 are attached from both sides of a cylindrical passage member 14 fitted into the space 1a of the grinding wheel head 1, and the feed screw 6 is screwed to the nut 4. The configuration is as follows. In this static pressure feed screw device 70, the passage member 14 is fixed to the grindstone table 1 by bolts 81 as shown in FIG. Further, the pair of nuts 4 are formed such that a pair of flange portions 84 formed at the end portions sandwich the passage member 14, and the passage members are formed by bolts 82 through elongated holes 85 opened in the flange portions. 14. As shown in FIG. 6, the long hole 85 is long and several places are opened in the circumferential direction. By rotating the nut 4, the angular phase of the nut 4 can be freely shifted and attached and fixed by the bolt 82. Have been able to. Thereby, the clearance between the inclined side surface portion 4b of the female screw convex portion 4a of the nut 4 and the inclined male screw side surface portion 6b of the male screw convex portion 6a of the feed screw 6 is set in a state where the nut 4, the feed screw 6 and the like are assembled. It is possible to easily and freely adjust it as it is. Next, the feed screw 6 will be described. FIG.
As shown in FIG. 5, the feed screw 6 is a trapezoidal screw whose male screw has a trapezoidal cross section. Then, in order to move the grindstone 1 at high speed, the lead is set to be large and the rigidity is set to be high. That is, as shown in FIG. 4, the width d of the male screw protrusion 6a of the feed screw 6 is set to be smaller than the width e of the female screw protrusion 4a of the nut 4. More specifically, d / e is set to be smaller than 2/3. With this setting, the pitch of the feed screw 6 is increased, and the lead is increased. The feed screw 6 is used to increase the pressure receiving area of a thrust static pressure pocket 7 which is a thrust direction static pressure support portion, which will be described later, to increase the thrust direction rigidity.
The tooth height c of the male screw protrusion 6a is increased. By doing so, the inertia generated by the rotation of the feed screw 6 increases. However, as described above, the increase in the inertia can be prevented by reducing the width d of the male screw protrusion 6a. The static pressure feed screw device 70 is provided with two types of static pressure pockets. That is, as shown also in the development view of FIG. 5, a spirally continuous thrust static pressure pocket 7 for supporting the static pressure in the thrust direction and a plurality of radial static pressure pockets for supporting the static pressure in the radial direction. The pressure pocket 10. As shown in FIGS. 2 and 3, the thrust static pressure pocket 7 is provided with a male screw convex portion 6 a of the feed screw 6.
Of the female screw side surfaces 4b and 4c of the nut 4 opposed to the male screw side surfaces 6b and 6c, a spiral is formed so as to open toward the flange portion 84 along the female screw side surface 4b facing the flange portion 84. It is formed as a continuous groove, and both ends are sealed with plugs 90. Accordingly, each of the thrust static pressure pockets 7 is formed on the female screw side face portions 4b of the pair of adjacent nuts 4 in opposite directions. As shown in FIG. 2, the thrust static pressure pocket 7 has a supply passage 8 formed in the passage member 14, an outer peripheral groove 9 formed in the outer periphery of the nut 4 communicating with the supply passage 8, and an outer peripheral groove 9 formed in the outer periphery. A thrust supply passage 13 formed from the groove 9 toward the thrust static pressure pocket 7 is connected to a pressure oil supply source such as a pump (not shown). Further, independent throttles 13a are attached near the opening ends of the thrust supply path 13 to the respective thrust static pressure pockets 7, respectively. The supply path 8 is connected to a supply path 1b provided in the grindstone table 1, and a pressure oil supply source (not shown) is connected to the supply path 1b via a flexible pipe as appropriate. As shown in FIG. 3, one set of the radial static pressure pockets 10 is provided for each of the nuts 4. Therefore, these two sets of radial static pressure pockets 1
The zero allows the hydrostatic feed screw device 70 to support both ends of the threaded portion of the feed screw 6. Each set of the radial static pressure pockets 10 is provided on an upper surface portion (top portion of a female screw crest) 4d of the female screw protrusion portion 4a of the nut 4 opposed to a lower surface portion (screw bottom portion of the male screw) 6d of the male screw concave portion of the feed screw 6. , Which are equally divided into one spiral. The radial static pressure pocket 10
Is preferably provided in three equal divisions (120 degree division) for one spiral, and the circumferential length of each radial static pressure pocket 10 is set to about 1/10 of the spiral circumference. Thus, the later-described centripetality can be maximized. In addition, by setting the lead length of the female screw (the top of the female screw thread) to be large, the radial static pressure pocket 10 can be increased, so that a larger radial static pressure (radial rigidity) can be obtained. Each of the radial static pressure pockets 10
Is similar to the static pressure pocket 7 for thrust,
Are connected to a pressure oil supply source such as a pump (not shown) by a supply path 8, an outer peripheral groove 9 of the nut 4, and a radial supply path 15 pierced from the outer peripheral groove 9 toward the radial static pressure pocket 10. ing. Also, this radial supply path 1
In the vicinity of the open end of each of the radial static pressure pockets 10 of FIG. 5, independent diaphragms 15a are attached. Therefore, the thrust static pressure pocket 7 and the radial static pressure pocket 10 can be adjusted to an arbitrary pressure by replacing the throttles 13a and 15a. The pressure oil supplied from the supply path 8 to the radial static pressure pocket 10 and the thrust static pressure pocket 7 through the outer peripheral groove 9 is supplied to a gap formed between the nut 4 and the feed screw 6. Through the nut 4. In order to smoothly discharge the pressurized oil, FIG.
As shown in FIG. 5, a groove 6e for discharging pressure oil is formed spirally along the root of the male screw convex portion 6a. The pressure oil discharged from the nut 4 is collected in a pressure oil recovery groove (not shown) provided on the base 60 in FIG. 1 and is reused. In FIG. 2, a discharge hole 14a formed on the passage member 14 corresponding to a position between the two nuts 4 is provided.
The pressure oil discharged between the nuts 4 is collected in a pressure oil recovery groove (not shown). The thrust static pressure pocket 7
Are sealed with a plug 90 to prevent a large amount of pressure oil from being directly discharged from the thrust static pressure pocket 7. The operation of this embodiment will be described based on the above configuration. When the feed screw 6 is rotated by the operation of the servomotor 63, the grindstone table 1 moves along the guide surface 60a.
In this case, the pressure supply source is driven, and pressure oil is supplied to the thrust static pressure pocket 7 through the supply path 8, the outer peripheral groove 9, the thrust supply path 13, and the throttle 13a. The supply path 8, the outer circumferential groove 9, the radial supply path 15, and the throttle 15a are also provided in each of the radial static pressure pockets 10.
Pressure oil is supplied via the. Thus, the male screw side surface portion 6b of the feed screw 6 and the female screw side surface portion 4
b, a static pressure of the pressurized oil is generated by the thrust static pressure pocket 7. Further, a static pressure of hydraulic oil is generated by the radial static pressure pocket 10 between the lower surface portion 6d of the male screw concave portion of the feed screw 6 and the upper surface portion 4d of the female screw convex portion 4a of the nut 4. Accordingly, the opposing static pressure pockets 7 for thrust formed on the pair of adjacent nuts 4 enable
The male screw convex portion 6a of the feed screw 6 is located at the center of the female screw side portions 4b and 4c of the nut 4 due to the centripetal action of the static pressure of the pressure oil generated in the opposite direction, and high thrust rigidity is obtained. The nuts 4 are attached to the respective nuts 4 in the direction of the center of the drawing, that is, in the direction opposite to the side of the flange portion 84 formed outside the respective nuts 4 by the pressure oil supplied to the thrust static pressure pocket 7. Therefore, the flange portion 84 is urged in a direction in which the flange portion 84 is pressed against the passage member 14. Therefore, the tension of the bolt 82 fixing the nut 4 is prevented from affecting the rigidity. The axial center of the feed screw 6 is located at the center of the axial center of the nut 4 by the centripetal action of the static pressure of the pressure oil generated in the three radially independent static pressure pockets 10 in the circumferential direction. , Nut 4 and feed screw 6 can be provided with high radial rigidity. In this manner, sufficient rigidity in the thrust direction and the radial direction can be obtained, and the rotational runout and vibration of the feed screw 6 are attenuated by the static pressure of the pressure oil. Becomes possible. In order to adjust the rigidity due to the static pressure in the thrust direction, the bolt 82 fixing at least one of the nuts 4 is loosened, and the nut 4 is inserted into the oblong hole 8.
5, the clearance between the female screw side surface portion 4b of the nut 4 and the male screw side surface portion 6b of the feed screw 6 can be adjusted, and the static pressure generated by the thrust static pressure pocket 7 can be adjusted. it can. That is, in FIG. 3, when the right nut 4 is rotated clockwise, the nut 4 acts on the feed screw 6 so as to move rightward, so that the nut provided with the thrust static pressure pocket 7 is provided. The clearance between the female screw side surface portion 4b and the male screw side surface portion 6b of the feed screw 6 becomes small. Therefore, since the pressure is increased, the rigidity in the thrust direction can be further increased. At this time, as described above, due to the centripetal force of the left and right thrust static pressure pockets 7, the male screw convex portion 6 a of the feed screw 6 causes the female screw side surface portion 4 b of the nut 4,
There is no need to adjust the left nut 4 because it is automatically located near the center of 4c. As shown in FIG. 6, a plurality of extra bolt holes 86 are formed in the communication member 14, so that
Even if the nut 4 is rotated beyond the length of the elongated hole 85, the bolt 85
It can be handled by changing the screwing location. As described above, in the present embodiment, the thrust static pressure pocket 7 is formed in a continuous spiral shape along the female screw side surface 4b of the nut 4. Therefore, most of the action of the thrust static pressure pocket 7 acts in the thrust direction, and serves as a static pressure pocket for obtaining rigidity in the thrust direction. Further, in the embodiment described above, the base 6
The moving body (grinding wheel base 1) is configured to move forward and backward by rotating the feed screw 6 with the servo motor 62 disposed above the moving object. However, the servo motor may be arranged on the moving body, the feed screw may be fixed on the base, and the moving body may be moved forward and backward by rotating a nut provided on the moving body by the servo motor. As an application modification of the present invention, as shown in FIG. 7, the side face portions 4b, 4c, 6b, 6 of the female screw convex portion 4a of the nut 4 and the male screw convex portion 6a of the feed screw 6 are provided.
By setting c to be a square screw 91 perpendicular to each axis, the static pressure generated by the thrust static pressure pocket 7 can all work as a rigid force in the thrust direction without waste. In the hydrostatic feed screw device according to the present invention, since the thrust static pressure pocket and the radial static pressure pocket are provided separately, sufficient rigidity in the radial direction can be obtained. In addition, since the radial static pressure pocket is formed to face the lower surface of the male screw recess of the feed screw, the depth of the radial static pressure pocket does not affect the size of the nut. The feed screw device can be downsized. Similarly, since a thrust static pressure pocket can be provided on the side surface of the female screw protrusion and a radial static pressure pocket can be provided on the upper surface of the same female screw protrusion, the length of the nut can be reduced, and the feed screw device can be provided. Can be reduced in size. In addition, since the nut acts by the static pressure of the thrust static pressure pocket so that the flange portion is pressed against the moving body, the tension of the bolt for mounting the nut affects the rigidity of the static pressure. There is no.
Further, since the thrust static pressure pocket has a continuous spiral shape, it is easy to work, and a uniform rigidity can be obtained in the thrust direction regardless of the processing accuracy. The nut is formed on the circumference of the flange.
Since the nut is fixed to the moving body via the elongated hole in the direction, the angular phase of the nut can be easily changed even when the nut and the feed screw are assembled to the moving body. Therefore, it is possible to easily adjust the rigidity in the thrust direction.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an overall view of a moving body feeding device according to an embodiment of the present invention. FIG. 2 is a sectional view of the hydrostatic feed screw device of the present embodiment. FIG. 3 is a cross-sectional view of the hydrostatic feed screw device of the present embodiment in a different phase from FIG. 2; FIG. 4 is a detailed view of a threaded portion between the nut 4 and the feed screw 6 according to the present embodiment. FIG. 5 is a development view of the nut 4 of the present embodiment. FIG. 6 is a cross-sectional view as viewed from a direction A in FIG. 3; FIG. 7 is a sectional view of a hydrostatic feed screw device showing an application modification of the present embodiment. FIG. 8 is a diagram for explaining a conventional technique. [Description of Signs] 1 Wheel head 1a Space 1b, 8 Supply path 4 Nut 4a Female screw convex part 4b, 4c Female screw side part 4d Upper part 6 Feed screw 6a Male screw convex part 6b, 6c Male screw side part 6d Lower part 7 Thrust static Pressure pocket 10 Radial static pressure pocket 9 Outer peripheral groove 13 Thrust supply path 13a, 15a Throttle 14 Passage member 14a Discharge hole 60 Base 60a Guide surface 61 Grinding wheel 62, 63 Servo motor 64 Ball bearing 65 Coupling 66 Connection part 70 Static Pressure feed screw device 81, 82 Bolt 84 Flange part 85 Long hole 86 Bolt hole 90 Filler plug 91 Square screw

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-78153 (JP, A) JP-A-4-39460 (JP, U) JP-A-61-82169 (JP, U) Field (Int.Cl. ⁷ , DB name) F16H 25/24

Claims (1)

(57) [Claim 1] A static pressure pocket for supplying pressure oil to a pair of adjacent nuts attached to a moving body and a threaded portion with a feed screw screwed to the nut is provided. In the provided double nut type static pressure feed screw device, a flange portion for attaching to the moving body with a bolt is formed at one non-opposite end of each of the pair of nuts,
A long slot is formed in the flange portion of at least one nut in the circumferential direction to pass the bolt so that the relative angular phase of the pair of nuts can be varied, and the static pressure is applied only in the thrust direction. A groove-shaped thrust static pressure pocket continuous in a spiral shape is formed on the side of the female screw of the pair of nuts on the side facing the respective flanges, and the static pressure is formed only in the radial direction. In order to exert pressure, a plurality of groove-shaped radial static pressure pockets equally divided in the circumferential direction are formed on the upper surface parallel to the axial direction of the convex portion of the female screw of the pair of nuts. Compression screw device.