JP2010196901A - Middle support for ball screw device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a middle support for a ball screw device, capable of shortening a distance (a supporting span) between a supporting bearing and itself while having simple construction for avoiding displacement and an excessive load on a screw shaft. <P>SOLUTION: The middle support is mounted on the screw shaft 1 of the ball screw device which includes the screw shaft 1 having a ball groove 2, a ball screw nut to be threaded to the ball groove 2 via a ball, and a circulating mechanism for circulating the ball between the ball screw nut and the screw shaft 1. It includes a clutch mechanism 30 provided between a supporting nut 20a which is threaded to the ball groove 2 of the screw shaft 1 via the ball 21 movably in the axial direction with the rotation of the screw shaft 1, and a member which is formed as part of a guide mechanism for guiding the nut 20a. The clutch mechanism 30 is put in a fastened condition to integrate the supporting nut 20a with the guide mechanism, but it is in a non-fastened condition to establish the idling condition of the supporting nut 20a. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement of an intermediate support of a ball screw device.

  If the rotation speed of the screw shaft constituting the ball screw device is close to the natural frequency of the screw shaft, it vibrates and vibrates vigorously, increasing the amplitude, which is dangerous. The rotational speed at this time is referred to as a critical speed, and this critical speed is inversely proportional to the square of the support span of the screw shaft. Therefore, the shorter the support span, the better.

  By the way, when the table stroke is long, such as an NC-controlled surface grinder, the screw shaft for feeding the table becomes long and the support span of the screw shaft becomes long. On the other hand, the screw shaft is used at a high rotation speed as the feed speed is increased. In this case, the above-described resonance cannot be avoided if the critical speed is in a low rotation range. Also, when the screw shaft rotates, a radial load acts on the end of the ball screw nut or screw shaft due to its own weight deflection, etc., and an excessive repetitive load (rotational bending stress) is applied to the screw shaft, resulting in the life of the ball screw. Adversely affect

  Therefore, in the past, an intermediate support that supports the middle portion of the screw shaft is provided to shorten the support span, thereby supporting the screw shaft at multiple points to make the dangerous speed a high rotation range on the safe side, The self-weight deflection of the screw shaft is reduced. As this type of conventional intermediate support, for example, as shown in Japanese Utility Model Laid-Open No. 2-4736, two slide bearings constituting the intermediate support are connected to each other between the support bearings that support both ends of the screw shaft. In this state, the ball screw nut is moved between the slide bearings so that the ball screw nut is moved by the rotation of the screw shaft, and one of the slide bearings is attached to the screw shaft. It is known that when a ball screw nut moving by rotation comes into contact, one of the slide bearings is pushed by the ball screw nut and moves together with the ball screw nut.

  However, in such an intermediate support, the structure is relatively simple. However, since the ball screw nut moves after contacting one of the slide bearings, the ball screw nut is positioned at an intermediate position of each slide bearing. During this period, the distance between the slide bearing and the support bearing (support span) cannot be shortened until the ball screw nut abuts against the slide bearing, and the critical speed cannot be increased too much. There is.

  Therefore, in order to solve such a problem, as shown in JP-A-6-129510, an intermediate support nut screwed to the screw shaft, an auxiliary screw shaft provided in parallel with the screw shaft, and the auxiliary screw shaft Auxiliary nuts that are screwed together and move in the axial direction by rotation of the auxiliary screw shaft, and an intermediate nut that is movably provided in the axial direction and supports the intermediate support nut rotatably and supports the auxiliary nut non-rotatably. A support frame, and by making the screw pitch of the auxiliary screw shaft and screw shaft the same so that the rotation speed of the auxiliary screw shaft is less than the rotation speed of the screw shaft, the intermediate support nut is not affected by the rotation of the screw shaft. It can be moved independently of the ball screw nut that is screwed onto the screw shaft only by rotation of the auxiliary screw shaft, so that the distance between the intermediate support nut and the support bearing (support That enables shortening of the span) are proposed.

Japanese Utility Model Publication 2-4736 JP-A-6-129510

  However, in this conventional technique, in addition to the intermediate support nut, an auxiliary screw shaft, an auxiliary nut, an intermediate support frame, a drive device for rotationally driving the auxiliary screw shaft, and the like are required. There is an inconvenience that it becomes high.

  The present invention has been made to eliminate such inconveniences, and it is possible to reduce the distance (support span) between the support bearing and the ball screw nut so as to be able to move independently. The structure can be manufactured at low cost, the load transmitted to the ball screw when the movement of the intermediate support is restricted can be reduced, and the displacement of the intermediate support can be easily corrected. Another object of the present invention is to provide an intermediate support for a ball screw device capable of reducing the wear of the thread groove and extending the life.

In order to achieve this object, an intermediate support of a ball screw device according to claim 1 includes a screw shaft having a spiral ball groove on an outer peripheral surface, and the screw shaft on an inner peripheral surface loosely fitted on the screw shaft. A ball screw nut including a ball screw nut having a ball groove corresponding to the ball groove and a plurality of balls fitted in a rollable manner between the ball grooves, and the ball is fitted to the ball screw nut. An intermediate support that is attached to the screw shaft of a ball screw device that is guided and circulated by a component, and that moves at a speed slower than the moving speed of the ball screw nut;
A support nut having a ball groove threadedly engaged with the ball groove of the screw shaft through a ball and having a lead angle set to 0 ° or a value close thereto, and the support nut is guided in parallel with the screw shaft And a clutch mechanism interposed between the guide mechanism and the support nut, and the guide mechanism includes a cylindrical nut housing in which the support nut is rotatably disposed, And at least a position restricting plate fixed to both ends of the nut housing, and the clutch mechanism is on the same circle centered on the shaft center on the surface facing the position restricting plate of the support nut. The engagement recess formed at a predetermined interval and the elastic body disposed in the through hole formed on the position restricting plate facing the engagement recess are biased toward the engagement recess. With a ball Wherein the said support nut of the through-hole, characterized in that it is composed of a pressing screw which is screwed into the end face of the opposite side.

  The intermediate support of the ball screw device according to claim 2 corresponds to the screw shaft having a spiral ball groove on the outer peripheral surface and the ball groove of the screw shaft on the inner peripheral surface loosely fitted to the screw shaft. A ball screw nut having a ball groove; and a plurality of balls fitted in a rollable manner between the both ball grooves, and the ball is guided and circulated by a ball circulation component fitted to the ball screw nut. An intermediate support that is attached to the screw shaft of the ball screw device and moves at a speed slower than the moving speed of the ball screw nut, screwed into the ball groove of the screw shaft via a ball, and having a lead angle. A support nut having a ball groove set to 0 ° or a value close thereto, a guide mechanism for guiding the support nut in parallel with the screw shaft, the guide mechanism, and the support nut. The support nut ball is screwed into a ball screw groove different from a ball screw groove into which the ball screw nut formed on the screw shaft is screwed, The guide mechanism includes at least a cylindrical nut housing in which the support nut is rotatably disposed, and position restriction plates fixed to both ends of the nut housing, respectively, and the clutch mechanism includes: An engagement recess formed on the surface of the support nut facing the position restriction plate on the same circle centered on the shaft center at a predetermined interval, and the position restriction plate side facing the engagement recess A ball urged toward the engaging recess by an elastic body disposed in the through hole formed in the through hole, and a push screw screwed to the end surface of the through hole opposite to the support nut It consists of And features.

  Here, the ball screw groove of the screw shaft is formed as a multi-thread thread groove, and the ball of the support nut is screwed into at least one of the thread grooves, and the ball screw nut ball is inserted into the remaining thread groove. Screwing is preferable.

According to the first aspect of the present invention, the clutch nut is interposed between the support nut screwed into the ball groove of the screw via the ball and the guide mechanism for guiding the support nut parallel to the screw shaft. Since it is inserted, the support nut and the guide mechanism are integrated by moving the clutch mechanism to the engaged state, and the support nut is moved along with the rotation of the screw shaft, and the support nut is moved to the non-engaged state. The nut can be idled to stop the movement of the support nut, the position of the support nut can be adjusted freely, and when the movement of the support nut is restricted, the engagement recess and this It is possible to reliably prevent an excessive load from being applied to the screw shaft by releasing the engaged state with the ball pressed by the elastic body engaged with the screw shaft.
Further, according to the invention of claim 2, in addition to the effect of the invention of claim 1, the ball of the support nut is a ball screw groove into which the ball screw nut formed on the screw shaft is screwed. Since it is screwed into different ball screw grooves, it is possible to reliably prevent the wear of the ball screw nut thread groove due to the ball of the support nut, and to prolong the life of the screw shaft. The effect that the optimal groove design for the nut can be performed is obtained.

It is the schematic which shows the example which used the intermediate support of the ball screw apparatus which is the 1st Embodiment of this invention for the linear motion guide apparatus. It is sectional drawing which expands and shows the clutch mechanism of an intermediate | middle support. It is a side view of the ball screw nut for support. FIG. 3 is a left side view of FIG. 2. It is explanatory drawing used for description of the formula which calculates | requires the moving speed of the axial direction of the ball screw nut for support. It is explanatory drawing for demonstrating operation | movement of an intermediate | middle support. FIG. 2 is a schematic view similar to FIG. 1 for explaining the operation of the first embodiment. It is a schematic block diagram which shows the example which used the intermediate support of the ball screw apparatus which is the 2nd Embodiment of this invention for a linear motion guide apparatus. It is sectional drawing of the intermediate support in 2nd Embodiment. FIG. 10 is a left side view of FIG. 9. FIG. 9 is a schematic configuration diagram similar to FIG. 8 for explaining an operation in the second embodiment. It is a block diagram which shows an example of the control apparatus in 2nd Embodiment. It is sectional drawing of the intermediate support which shows the 3rd Embodiment of this invention. The ball interposed between the ball groove of the support ball screw nut and the ball groove of the screw shaft applicable to the third embodiment is one point on the ball groove side of the support ball screw nut, and the ball groove of the screw shaft. It is explanatory drawing for demonstrating the state which is contacting in 2 points | pieces by the side.

  Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a schematic view showing an example in which an intermediate support of a ball screw device as an example of an embodiment of the present invention is used in a linear motion guide device, and FIG. 2 is an enlarged sectional view showing a clutch mechanism of the intermediate support. 3 is a side view of the support ball screw nut, FIG. 4 is a left side view of FIG. 2, FIG. 5 is an explanatory view used to explain an equation for determining the moving speed of the support ball screw nut in the axial direction, and FIG. It is explanatory drawing for demonstrating operation | movement of.

  First, for the convenience of explanation, the linear motion guide device will be described first. In FIG. 1, reference numeral 1 denotes a relatively long screw shaft of the ball screw device, and the screw shaft 1 has a spiral ball groove ( 2 thread 2). A ball screw nut 3 having a ball groove (not shown) corresponding to the ball groove 2 of the screw shaft 1 is loosely fitted to the screw shaft 1 on the inner peripheral surface. A large number of balls (not shown) are fitted between the ball groove 2 of the screw shaft 1 and the ball groove of the ball screw nut 3 so as to be able to roll, and the balls are fitted to the ball screw nut 3. It is guided and circulated by a ball circulation part (not shown).

  Both ends of the screw shaft 1 are rotatably supported by support bearings (not shown) in two bearing housings 5a and 5b attached to the bed 4, and one (left) shaft end is a cup. It is connected via a ring 6 to a rotary drive device 7 constituted by a step motor or the like. Further, the ball screw nut 3 is fitted in the nut housing 8, and the rotation of the screw shaft 1 in the circumferential direction is regulated by a feed guide 9 in which the lower portion of the nut housing 8 is constituted by a linear guide, for example. Guided in the left-right direction, and a table 10 is attached to the top of the nut housing 8.

  Next, an intermediate support that is an example of an embodiment of the present invention will be described. The intermediate support includes a pair of support ball screw nuts 20a and 20b screwed into the ball groove 2 of the screw shaft 1 via balls 21 (see FIG. 2) at both axial positions of the ball screw nut 3. . Since the support ball screw nuts 20a and 20b have the same configuration, the support ball screw nut 20a will be described with reference to FIGS.

  The ball groove 22 of the support ball screw nut 20a has a circumferential groove, that is, a lead angle of “0 °” and is provided in a plurality of locations (here, four locations) in the axial direction. Is set to an appropriate minimum pitch (in this embodiment, 1/2 of the thread pitch of the ball groove 2 of the screw shaft 1). A cylindrical retainer 23 made of resin, brass, or the like is interposed between the inner diameter surface of the support ball screw nut 20a and the outer diameter surface of the screw shaft 1.

  In the retainer 23, the ball groove 2 of the screw shaft 1 is a double thread, and the screw pitch of the ball groove 22 of the support ball screw nut 20a is 1/2 of the screw pitch of the ball groove 2 of the screw shaft 1. , Two holes 24 are formed that are spaced apart from each other by 180 ° in the circumferential direction, and the two holes 24 correspond to the thread pitch of the ball groove 22 while shifting the phase by 90 ° alternately in the axial direction. And four places are arranged. The hole 24 is for holding the ball 21 sandwiched between the ball groove 22 and the ball groove 2 in a rollable manner, and is the same as that used in a known non-circulating ball screw device.

  The support ball screw nut 20a having such a configuration is rotatably disposed on the inner peripheral surface of a cylindrical nut housing 25, and is provided by position restricting plates 26 and 27 that are bolted to both ends of the nut housing 25, respectively. Axial movement is restricted. Further, the nut housing 25 is loosely fitted in the center of the moving body 28 guided by the feed guide 9 described above, and the position restricting plate 26 is bolted to the moving body 28.

  Here, in this embodiment, the feed guide 9, the nut housing 25, the position regulating plates 26 and 27, and the moving body 28 constitute a guide mechanism. A clutch mechanism 30 is disposed between the position restricting plate 26 and the support ball screw nut 20a facing the position restricting plate 26. As shown in FIG. 3, the clutch mechanism 30 has a large number of cones formed on the same surface centering on the shaft center at predetermined intervals on the surface of the support ball screw nut 20a facing the position restricting plate 26. As shown in FIGS. 2 and 4, the engaging recess 31 is engaged by a coil spring 33 disposed in a through hole 32 formed on the position regulating plate 26 side facing each engaging recess 31. The ball 34 is urged toward the concave portion 31 side, and a push screw 35 that adjusts the elastic force of the spring 33 screwed to the end surface of the through hole 32 opposite to the support ball screw nut 20a. .

Next, the relationship between the rotational speed of the screw shaft 1 and the axial movement speed of the support ball screw nuts 20a and 20b will be described with reference to FIGS. Here, Ni: rotational speed of the screw shaft (rpm), Nc: ball revolution (around the screw shaft) speed (rpm), Nr: ball rotation speed (rpm), l: screw shaft lead (mm), α ₁ : Ball contact angle on the ball groove raceway surface on the screw shaft side (°), α ₂ : Ball contact angle on the ball groove raceway surface on the support ball screw nut side (°), dm: B. C. When D (center diameter of the steel ball) (mm) and Da: ball diameter (mm), when the screw shaft rotates at the rotation speed Ni, point A on the ball groove raceway surface of the screw shaft side (see FIG. 5) The axial travel distance Li _S per unit time of
Li _S = [{π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 · Ni (1)
The movement distance Lr _{S in} the axial direction of the ball per unit time due to the rotation of the ball at point A on the ball groove raceway surface on the screw shaft side is:
Lr _S = πDa cosα ₁ Nr (2)
The axial movement distance Lc _S per unit time of the ball due to the revolution of the ball at the point A on the ball groove raceway surface on the screw shaft side is:
Lc _S = [{π (dm−Da cos α ₁ )} ² + l ² ] ^1/2 · Nc (3)
Ball travel distance Lr _n per unit time due to the rotation of the ball at point B on the ball groove raceway surface on the ball screw nut side for support is
Lr _n = πDa cosα ₂ Nr (4)
Moving distance Lc _n axial per unit of ball time by the revolution of the ball on the support for the ball screw nut-side ball on the groove track surface point B,
Lc _n = [{π (dm + Da cosα ₂ )} ² + l ² ] ^1/2 · Nc (5)
It becomes.

Here, when the ball screw nut for support is fixed and the screw shaft rotates and the ball rolls, the ball and the screw shaft roll, so the moving speed of the ball and the screw shaft in the axial direction at the contact point A Are the same and the ball and screw shaft will travel the same distance in the axial direction. Accordingly, the axial movement distance Li _S of the point A on the ball groove raceway surface on the screw shaft side is the sum of the movement distance Lr _S due to the ball rotation and the movement distance Lc _S due to the ball revolution (Li _S = Lr _S + Lc _S ) And is represented by the following equation.
[{Π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 · Ni
= ΠDa cosα ₁ Nr + [{π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 · Nc (6)

On the other hand, since the support ball screw nut is fixed, the axial movement distance of the point B on the ball groove raceway surface on the support ball screw nut side is zero, and the contact point B of the ball is on the screw shaft side. considered like the contact point a is so reverse the direction of the revolution and rotation of the ball 0 = -Lr _n + Lc _n next, is expressed by the following equation.
0 = −πDa cosα ₂ Nr + [{π (dm + Da cosα ₂ )} ² + l ² ] ^1/2 · Nc (7)
From the equations (6) and (7), the ball revolution speed Nc and the rotation speed Nr are respectively expressed by the following equations.
Nc = cosα ₂ [{π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 · Ni / [cosα ₁ [{π (dm + Da cosα ₂ )} ² + l ² ] ^1/2 + cosα ₂ [{π (Dm−Da cos α ₁ )} ² + l ² ] ^1/2 ] (8)
Nr = [[{π (dm + Da cosα ₂ )} ² + l ² ] ^1/2 · Nc] · Ni / πDa cosα ₂ (9)
When the support ball screw nut is fixed and the screw shaft rotates and the lead angle of the ball groove on the support ball screw nut side is “0 °”, the axial movement distance of the support ball screw nut is the ball axis. Since it is the same as the moving distance in the direction, the moving speed v in the axial direction of the support ball screw nut is expressed by the following equation.
v = cosα ₂ [{π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 · Ni · l / [cosα ₁ [{π (dm + Da cosα ₂ )} ² + l ² ] ^1/2 + cosα ₂ [ {Π (dm−Da cosα ₁ )} ² + l ² ] ^1/2 ] (10)

Here, as shown in FIG. 1, the ball guide nuts 20a and 20b are used for the linear motion guide device so that dm: 26 mm, l: 50 mm, Da: 3.9688 mm, and the ball on the screw shaft 1 side. Both the groove 2 and the ball groove 22 on the support ball screw nuts 20a, 20b side are formed in a Gothic arch shape so that the ball 21 contacts at two points on the ball groove 2 side and at two points on the ball groove 22 side (four points in total). , Α ₁ : 45 °, α ₂ : 45 °, the moving speed of the ball screw nut 3 in the axial direction is Ni · l, whereas the axial speed of the supporting ball screw nuts 20a and 20b is The moving speed v is 0.46 Ni · l from the equation (10). That is, when the screw shaft 1 makes one rotation, the ball screw nut 3 advances by one lead in the axial direction, whereas the support ball screw nuts 20a and 20b are approximately ½ of the moving distance of the ball screw nut 3. Will only proceed in the axial direction.

  Next, the operation of the intermediate support will be described with reference to FIG. First, at the time of assembly, one sliding screw nut 20a of the pair of support ball screw nuts 20a and 20b screwed into the ball groove 2 of the screw shaft 1 is inserted between the ball screw nut 3 and the bearing housing 5a. The other support ball screw nut 20b is positioned at the approximate center between the ball screw nut 3 and the bearing housing 5b.

  In this case, the adjustment of the positions of the support ball screw nuts 20a and 20b is performed by loosening the push screw 35 of the position restricting plate 26 and rotating the screw shaft 1 in a state where the rotation of the screw shaft 1 is stopped. In this state, by moving the moving body 28 in the axial direction, the support ball screw nuts 20a and 20b are idled around the screw shaft 1 and adjusted to a predetermined position. When the movement of the movable body 28 is restricted by tightening the push screw 35 and adjusting the elastic force of the spring 33 in a state in which the engagement recess 34 is engaged with the engagement recess 31, the support ball screw nut 20a or 20b is controlled. Adjusts the rotational torque at which starts spinning.

When the screw shaft 1 is rotated by the rotary drive device 7 in this state, the ball screw nut 3 moves along the screw shaft 1 while being guided by the linear guide device 10, and the support ball screw nuts 20a and 20b are moved. It moves along the screw shaft 1 in the same direction as the ball screw nut 3 while being guided by the feed guide 9. At this time, the moving speed v of the support ball screw nuts 20a and 20b is approximately ½ of that of the ball screw nut 3 as described above, and therefore the support ball screw is independent of the position of the ball screw nut 3 in the axial direction. The nut 20a is always positioned approximately at the center between the ball screw nut 3 and the bearing housing 5a, and the support ball screw nut 20b is always positioned approximately at the center between the ball screw nut 3 and the bearing housing 5b. (In FIG. 6, L ₁ : L ₂ ≈1: 1 and L ₃ : L ₄ ≈1: 1).

  As a result, as shown in FIG. 6, the distance (support span) between the support ball screw nut 20a and the bearing housing 5a is shortened as the ball screw nut 3 moves toward the bearing housing 5a, and the support The distance (support span) between the ball screw nut 20b and the bearing housing 5a is shortened. As a result, the dangerous speed can be set to a safe rotation range and the screw shaft 1 is supported at multiple points. As a result, the self-weight deflection of the screw shaft 1 can be reduced.

  In addition, the support ball screw nut 20a is always positioned approximately at the center between the ball screw nut 3 and the bearing housing 5a, and the support ball screw nut 20b is always positioned approximately between the ball screw nut 3 and the bearing housing 5b. Since it can be located in the center, the axial movement amount of the ball screw nut 3 until the support ball screw nuts 20a and 20b interfere with the ball screw nut 3 and the bearing housings 5a and 5b can be increased. As a result, it can be made suitable for an NC-controlled surface grinder with a long table stroke.

Furthermore, since it is only necessary to screw the ball screw nuts 20a and 20b for support into the ball groove 2 of the screw shaft 1, an intermediate support system is provided that can perform effective vibration suppression with a simple structure and low cost. can do. As described above, the support ball screw nuts 20a and 20b move at half the moving speed of the ball screw nut 3 with the rotation of the screw shaft 1, and this movement is caused by the rolling elements, the screw shaft and the nut. Since it is performed by friction between the two, slippage always occurs during movement.
This slip is affected by the groove shape, the moving speed, the moving acceleration, the frictional resistance of the fixed table, and the like. For this reason, if the ball screw nut 3 is moved for a long time, the position of the support ball screw nut is displaced. For this reason, when the ball screw nut 20a for support has shifted to the left from the center between the ball screw nut 3 and the bearing housing 5a, for example, when the ball screw nut 3 moves to the left end side, Even within the allowable movement range, as shown in FIG. 7, the bolt head fixing the position restricting plate 26 that restricts the axial position of the support ball screw nut 20a contacts the bearing housing 5a. The case where it touches occurs.
In this state, the leftward movement of the support ball screw nut 20a is prevented by the bearing housing 5a. Therefore, when the rotation of the screw shaft 1 is continued, rotational torque is transmitted to the support ball screw nut 20a. Therefore, when this rotational torque exceeds the allowable rotational torque set by the elastic force of the spring 33 of the clutch mechanism 30, the ball 34 is pushed leftward from the engaging recess 31, and the support ball screw nut 20a is It is possible to prevent the screw housing 1 from being overloaded due to the idling state with respect to the nut housing 25.

  Similarly, when the support ball screw nut 20b is displaced to the right side from the middle between the ball screw nut 3 and the bearing housing 5b, the support ball screw nut 20b comes into contact with the bearing housing 5b. It is possible to prevent the screw nut 20b from idling and applying an excessive load to the screw shaft 1.

Further, when the support ball screw nut 20a or 20b is displaced on the ball screw nut 3 side and interferes with the ball screw nut 3, the support ball screw nut 20a or 20b is idled to the screw shaft 1. An excessive load can be prevented.
As described above, when the support ball screw nut 20a and / or 20b is displaced, the support ball screw is lowered by loosening the push screw 35 and reducing the elastic force of the spring 33 in the same manner as described above. The nut 20a and / or 20b can be easily idled to correct the displacement, and a rotational torque greater than the rotational torque set by the elastic force of the spring 33 can be generated without loosening the push screw 35. The displacement can be corrected by moving the moving body 28.

  In addition, in the said 1st Embodiment, although the case where the ball | bowl 34 was pressed with the coil spring 33 was demonstrated, it is not limited to this, Other springs, such as a leaf | plate spring, can be applied, You may make it apply other elastic bodies, such as rubber | gum. In the first embodiment, the case where the engagement recess 31 and the ball 34 are engaged has been described. However, the present invention is not limited to this, and the engagement recess 31 and the ball 34 are omitted to replace the friction. The plate may be brought into contact with the end faces of the support ball screw nuts 20a and 20b with a spring.

  Furthermore, in the first embodiment, the case where the elastic force of the spring 33 is adjusted by the tightening position of the push screw 35 has been described. However, the present invention is not limited to this. A spring seat may be provided, and the elastic force of the spring 33 may be adjusted by changing the thickness of the spring seat.

Next, a second embodiment of the present invention will be described with reference to FIGS. In the second embodiment, the on / off state of the clutch mechanism is arbitrarily controlled.
That is, in the second embodiment, instead of the case where the intermediate support clutch mechanism 30 is configured by the engagement recess 31, the spring 33, the ball 34, and the set screw 35 in the first embodiment, FIG. 9 and FIG. As shown, a pair of air cylinders 40 and 41 are arranged symmetrically on a line passing through the center of the position restricting plate 26 opposite to the support ball screw nut 20a, and springs (see FIG. The friction plate 43 formed at the tip of the piston rod 42 urged to the extension side by a notch) is configured to face the end surface of the support ball screw nut 20a through the through hole 44 formed in the position restricting plate 26. Yes.
Here, by supplying pressurized air to the air cylinders 40 and 41 through the flexible pipe 45, the piston rod 42 is contracted, and the friction plate 43 is separated from the end surface of the support ball screw nut 20a to be in an unfastened state. In this state, the free rotation of the support ball screw nut 20a is allowed, and from this state, the supply of pressurized air to the air cylinders 40 and 41 is cut off to the exhaust state, whereby the piston rod 42 is extended by the spring. Thus, the friction plate 43 is brought into a fastening state in which the friction plate 43 is pressed against the end surface of the support ball screw nut 20a, and the support ball screw nut 20a is integrally fixed to the nut housing 25.

  In addition, as shown in FIG. 8, the bearing housing 5a has ultrasonic waves that measure the distance by measuring the time from when the ultrasonic wave or laser beam is irradiated to when the reflected wave or reflected light is received or received. Two distance sensors 50 and 51 constituted by a distance measuring device or a laser distance measuring device are arranged, and the distance sensor 50 measures the distance to the left end of the table 10 attached to the ball screw nut 3. The distance to the left end of the table 29 attached to the support ball screw nut 20a is measured.

Further, a distance sensor 53 similar to the distance sensors 50 and 51 is disposed in the bearing housing 5b, and the distance sensor 53 measures the distance to the right end of the table 29 attached to the support ball screw nut 20b.
Then, the distance detection values of the distance sensors 50 to 51 are input to the control device 55 as shown in FIG. 12, and based on the distance detection values of the ball screw nut 3 detected by the distance sensor 50 by the control device 55. When the target distances La ^* and Lb ^* of the ball screw nuts 20a and 20b for support are calculated and the calculated target distances La ^* and Lb ^* and the distance detection values La and Lb detected by the distance sensors 51 and 52 are inconsistent That is, when the support ball screw nuts 20a and 20b are displaced, the support balls are adjusted so that the target distances La ^* and Lb ^* coincide with the detection distances La and Lb in consideration of the rotation direction of the screw shaft 1. While controlling the actuators 53 and 54 for supplying and discharging the pressurized air to and from the air cylinders 40 and 41 with respect to the screw nuts 20a and 20b, the distance When the output values La and Lb are equal to or less than the preset minimum set distance Lmin, it is determined that there is an approach error, and the actuators 53 and 54 are controlled to be in a pressurized air supply state so that pressurized air is applied to the air cylinders 40 and 41. Supply.

  According to the second embodiment, the position of the ball screw nut 3 is always detected by the distance sensor 50, and the positions of the support ball screw nuts 20a and 20b are always detected by the distance sensors 51 and 52. In a state where the ball screw nuts 20a and 20b are in a normal position without causing a positional shift, the actuators 43 and 54 are controlled to be in an exhaust state, and the pressurized air is maintained in an exhaust state from the air cylinders 40 and 41. Therefore, the piston rod 42 is extended by the elastic force of the spring, the friction plate 43 is pressed against the support ball screw nuts 20a and 20b, and the clutch mechanism 30 is brought into a fastening state, and the support ball screw nuts 20a and 20b are connected to the nut housing 25. Is fixed integrally with the ball screw nut 3 according to the rotation of the screw shaft 1. Moving at half the speed of the moving speed.

For example, in the case where a position shift occurs such that the support ball screw nut 20a is closer to the bearing housing 5a from this normal state, the screw shaft 1 is rotationally driven so that the ball screw nut 3 moves toward the bearing housing 5a. Then, the actuator 53 is controlled to be supplied, pressurized air is supplied to the air cylinder 40, and the piston rod 42 is contracted against the spring, whereby the friction plate 43 and the ball screw nut 20a for support are moved. By separating the clutch mechanism 30 from the non-engaged state, thereby enabling the support ball screw nut 20a to idle with respect to the nut housing 25, the moving distance of the support ball screw nut 20a is reduced, and the distance sensor 51 Is detected based on the distance detection value L of the ball screw nut 3. By exhausting pressurized air from the air cylinder 40 at the time of the match with the target distance La ^* calculated by controlling the actuator 53 to the exhaust state, to return the clutch mechanism 30 to the engaged state, support for the ball screw nut 20a Is returned to a normal moving state in which the ball screw nut 3 moves at a moving speed half the moving speed of the ball screw nut 3.

  Conversely, when the support ball screw nut 20a is displaced toward the ball screw nut 3, the screw shaft 1 is driven to rotate so that the ball screw nut 3 moves toward the bearing housing 5b. The actuator 53 is controlled to be in a pressurized supply state, pressurized air is supplied to the air cylinder 40 so that the clutch mechanism 30 is in a non-engaged state, and the support ball screw nut 20a is in an idle state with respect to the nut housing 25. By adjusting the position by reducing the moving speed of the ball screw nut 20a to the right, the actuator 53 is controlled to be in the exhausted state when the normal position is reached, and the compressed air is exhausted from the air cylinder 40. Then, by controlling the clutch mechanism 30 to the engaged state, the support ball screw nut 20a is returned to the normal moving speed. .

  Similarly, when a positional deviation occurs in the support ball screw nut 20b, the positional deviation is corrected by setting the clutch mechanism 30 in the non-engaged state when the screw shaft 1 is in a rotational direction in which the positional deviation can be corrected. When the positional deviation is resolved, the clutch mechanism 30 is returned to the engaged state, and the support ball screw nut 20b is returned to the normal moving speed.

  Further, when the distance detection value La or Lb of the support ball screw nut 20a or 20b becomes equal to or smaller than the minimum set distance Lmin, the clutch mechanism 30 is brought into the non-engaged state, and the support ball screw nut 20a or 20b is inserted into the nut housing 25. On the other hand, it is possible to prevent the support ball screw nut 20a or 20b from coming into contact with the bearing housing 5a or 5b in an idle state, and it is possible to prevent an excessive load from being applied to the screw shaft 1. .

In the second embodiment, the case where a spring-loaded air cylinder is applied as the clutch mechanism 30 has been described. However, the double-acting air cylinder is applied to expand and contract the piston rod and pressurize air at different ends. You may make it carry out by supplying.
In the second embodiment, the case where the clutch mechanism 30 is configured by an air cylinder has been described. However, the present invention is not limited thereto, and may be configured by another fluid cylinder such as a hydraulic cylinder. In addition, an electric actuator such as an electromagnetic solenoid may be applied, and an electromagnetic clutch, an electromagnetic powder clutch, or the like may be further applied.

  In the first and second embodiments, the case where the lead angle of the support ball screw nuts 20a and 20b is set to “0 °” has been described. The angle does not need to be “0 °” and can be set to a value near “0 °”. In particular, in the second embodiment, the position of the support ball screw nuts 20a and 20b is used by the clutch mechanism 30. Therefore, the lead angle is set to an angle larger than “0 °”, the moving speed of the support ball screw nuts 20a and 20b is increased, and the position of the target distance is controlled by the clutch mechanism 30. May be.

  Next, a third embodiment of the present invention will be described with reference to FIG. In the third embodiment, in the first and second embodiments, the ball groove 2 of the screw shaft 1 is shared by the balls of the ball screw nut 3 and the balls of the support ball screw nuts 20a and 20b. As described above, instead of this, both are rolled into different ball grooves.

  That is, in the third embodiment, as shown in FIG. 13, in the first embodiment described above, two screw grooves 2a and 2b are formed in the screw shaft 1, and a ball screw nut is formed in one screw groove 2a. 3 is rolled, and the ball 21 of the support ball screw nuts 20a and 20b is rolled in the other screw groove 2b.

  According to the third embodiment, since the ball of the ball screw nut 3 and the ball 21 of the support ball screw nuts 20a and 20b roll in different thread grooves 2a and 2b of the screw shaft 1, The balls 21 of the ball screw nuts 20a and 20b can be reliably prevented from wearing the screw groove 2a, the life of the screw groove 2a can be extended, and the screws of the support ball screw nuts 20a and 20b can be extended. The groove 2b can be designed to have an optimum groove shape and roughness for the ball screw nuts 20a and 20b for support, and the degree of freedom in designing the groove can be improved.

That is, in the first and second embodiments, the ball groove 2 on the screw shaft 1 side and the ball groove 22 on the support ball screw nut 20a, 20b side are both Gothic arch shapes, and the ball 21 is a ball groove. The case where contact is made at 2 points on the 2 side and 2 points on the ball groove 22 side (4 points in total) is taken as an example, but instead of this, as shown in FIG. 14, the ball groove on the screw shaft 1 side is used. the second shape with contacting the ball 21 as Gothic arch shape two points P _1, P ₂ of the ball groove 2 side, support for the ball screw nut 20a, and 20b side shape of the ball groove 22 as a single R shape The ball 21 is brought into contact with the ball groove 22 at one point P ₃ (three points in total) to apply a light preload, thereby obtaining a stable movement of the ball 21 and thus the ball screw nuts 20a and 20b for support. You can.

  More specifically, when the lead angles of the ball groove 2 of the screw shaft 1 and the ball grooves 22 of the support ball screw nuts 20a and 20b are different from each other, rolling motion occurs between the ball 21 and each of the ball grooves 2 and 22. In addition, the sliding movement increases. In the case of a conventional non-circulating ball screw device, the ball groove on the screw shaft side and the ball groove on the nut side are both the same in a Gothic arch shape, so the ball is two points on the ball groove on the screw shaft side, The ball groove contacted at 2 points, a total of 4 points, and sliding friction was large.

Referring to FIG. 14, when the ball 21 rolls at two points P ₁ and P ₂ of the ball groove 2 of the screw shaft 1, the direction of the vector a is on the support ball screw nut 20a (20b) side. However, since the ball 21 on the nut side has a lead angle of 0 °, the ball 21 advances in the direction of the vector b. That is, the difference between the vector a and the vector b (vector c) becomes a slip of the ball 21, and when the ball 21 is brought into contact with the ball groove 22 at two points, this slip cannot be absorbed well, Sliding friction will increase.

On the other hand, as shown in FIG. 14, the shape of the ball groove 2 on the screw shaft 1 side is a Gothic arch shape, and the ball 21 is brought into contact at two points P ₁ and P ₂ on the ball groove 2 side. screw nut 20a, if the shape of the ball groove 22 of the 20b side is brought into contact with one point P ₃ of the ball 21 in the ball groove 22 side (a total of 3 points) as a single R-shape so as make a lighter preload ball 21 Are in contact at points P ₁ , P ₂ , P ₃ , of which a rolling motion occurs at points P ₁ , P ₂ on the ball groove 2 side of the screw shaft 1, and around the contact point at point P ₃ on the ball groove 22 side. The rolling motion is accompanied by a rotational slip, and the difference between the vector a and the vector b (vector c) is absorbed by the rotational slip, whereby the sliding friction is reduced, and the ball 21 and thus the ball screw nuts 20a, 20 for support are supported. A stable movement of b can be obtained.

When the balls 21 of the support ball screw nuts 20a and 20b used in the linear motion guide device of FIGS. 1 and 8 are brought into contact at three points, dm: 26 mm, l: 50 mm, Da: 3.9688 mm, α _{If 1} : 45 ° and α ₂ : 0 °, the axial movement speed v of the ball screw nut 3 is Ni · l, whereas the axial movement speed v of the support ball screw nuts 20a, 20b is From the equation (10), 0.54 Ni · l is obtained. In this case as well, the ball screw nut 3 advances by one lead in the axial direction when the screw shaft 1 makes one rotation, as in the above embodiment. The support ball screw nuts 20a and 20b are moved in the axial direction by about ½ of the moving distance of the ball screw nut 3, and the same effect as the above embodiment can be obtained.

  In the third embodiment, the case where the double thread is applied to the first embodiment has been described. However, the present invention is not limited to this, and the double thread may be applied to the second embodiment. Needless to say, it is good. Moreover, in the said 3rd Embodiment, although the case where the double thread groove was formed in the screw shaft 1 was demonstrated, it is not limited to this, A triple thread groove is formed in the screw shaft 1, Two of them are used for ball screw nuts, and the other one is used for support ball screw nuts. Three thread grooves are used for ball screw nuts, support ball screw nuts 20a, and support ball screw nuts, respectively. Further, a four-thread groove is formed on the screw shaft 1, two of which are for the ball screw nut 3, and the other two are support ball screw nuts 20a and 20b. Three screw grooves for the ball screw nut 3, the remaining one screw groove for the support ball screw nuts 20a and 20b, and one screw groove for the ball screw nut 3. The remaining three screw grooves can be used for the support ball screw nuts 20a and 20b. In short, a multi-thread screw groove is formed on the screw shaft 1, and the ball screw nut 3 and the support ball screw nuts 20a and 20b are formed. Different thread grooves may be used.

  Further, in each of the above embodiments, the case where the two ball screw nuts 20a and 20b for support are screwed into the ball groove 2 of the screw shaft 1 is taken as an example, but the present invention is not limited to this. Even if the support ball screw nut 20a is screwed only to the support end side (right end side) of 1, the large vibration damping effect can be obtained. Further, in each of the above embodiments, the left end side of the screw shaft 1 is the support end, but this may be a fixed end or a free end.

DESCRIPTION OF SYMBOLS 1 ... Screw shaft 2 ... Ball groove 3 of screw shaft ... Ball screw nut 20a, 20b ... Support ball screw nut 21 ... Ball 22 on support ball screw nut side ... Ball groove 25 on support ball screw nut side ... Nut housing 26, 27 ... Position restricting plate 30 ... Clutch mechanism 31 ... Engaging recess 33 ... Spring 34 ... Ball 35 ... Push screw 40, 41 ... Air cylinder 42 ... Piston rod 43 ... Friction plates 50-52 ... Distance sensors 53, 54 ... Actuator 55 ... Control devices 2a, 2b ... Thread groove

Claims (2)

A screw shaft having a spiral ball groove on the outer peripheral surface, a ball screw nut having a ball groove corresponding to the ball groove of the screw shaft on an inner peripheral surface loosely fitted on the screw shaft, and between the two ball grooves A plurality of balls fitted so as to be able to roll, and the balls are attached to the screw shaft of a ball screw device that circulates by being guided by a ball circulation component fitted to the ball screw nut, and the balls An intermediate support that moves at a speed slower than the moving speed of the screw nut,
A support nut having a ball groove threadedly engaged with the ball groove of the screw shaft through a ball and having a lead angle set to 0 ° or a value close thereto, and the support nut is guided in parallel with the screw shaft And a clutch mechanism interposed between the guide mechanism and the support nut,
The guide mechanism is configured to include at least a cylindrical nut housing in which the support nut is rotatably disposed, and position restriction plates fixed to both ends of the nut housing,
The clutch mechanism includes an engagement recess formed on the surface of the support nut facing the position restricting plate on the same circle centered on the shaft center at a predetermined interval, and opposed to the engagement recess. The ball urged to the engagement recess side by an elastic body disposed in the through hole formed on the position regulating plate side and the end surface of the through hole opposite to the support nut are screwed together. An intermediate support for a ball screw device, characterized by comprising A screw shaft having a spiral ball groove on the outer peripheral surface, a ball screw nut having a ball groove corresponding to the ball groove of the screw shaft on an inner peripheral surface loosely fitted on the screw shaft, and between the two ball grooves A plurality of balls fitted so as to be able to roll, and the balls are attached to the screw shaft of a ball screw device that circulates by being guided by a ball circulation component fitted to the ball screw nut, and the balls An intermediate support that moves at a speed slower than the moving speed of the screw nut,
A support nut having a ball groove threadedly engaged with the ball groove of the screw shaft through a ball and having a lead angle set to 0 ° or a value close thereto, and the support nut is guided in parallel with the screw shaft And a clutch mechanism interposed between the guide mechanism and the support nut,
The ball of the support nut is screwed into a ball screw groove different from the ball screw groove into which the ball screw nut formed on the screw shaft is screwed,
The guide mechanism is configured to include at least a cylindrical nut housing in which the support nut is rotatably disposed, and position restriction plates fixed to both ends of the nut housing,
The clutch mechanism includes an engagement recess formed on the surface of the support nut facing the position restricting plate on the same circle centered on the shaft center at a predetermined interval, and opposed to the engagement recess. The ball urged to the engagement recess side by an elastic body disposed in the through hole formed on the position regulating plate side and the end surface of the through hole opposite to the support nut are screwed together. An intermediate support for a ball screw device, characterized by comprising

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