JP2006161868A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator for miniaturizing a device and preventing the vibration and breakage. <P>SOLUTION: The actuator is constructed to drive the rotation of a feed screw shaft rotatably supported at both ends by a pair of bearing members arranged on a base, fix a feed screw nut threaded to the feed screw shaft to a moving body, and move the moving body following a guide rail provided on the base along the feed screw shaft. Between the moving body 8 and each of the bearing members 5a, 5b on both sides, a pair of intermediate supports 20A, 20B are mounted movably on the feed screw shaft 1 for supporting the radial load of the feed screw shaft 1 in linkage with the moving body 8 in the direction of the feed screw shaft 1. Thus, the movement of the moving body 8 is transmitted to the intermediate supports 20A, 20B via a rack and pinion mechanism. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an actuator that can reduce the size of an apparatus and prevent vibrations from being generated or broken.

In general, the conventional actuator has a configuration as shown in FIG. 7, for example.
First, there is a base 201, and a ball screw 203 is disposed on the base 201. The both ends of the ball screw 203 are rotatably supported by bearing members 205 and 207 installed on the base 201. A motor 209 is disposed, and the ball screw 203 is connected to the output shaft of the motor 209 via a coupling mechanism (not shown). A ball screw nut 211 is screwed onto the ball screw 203, and a slider 213 is attached to the ball screw nut 211. The slider 213 includes a slider main body 215 and a guide block 217 attached to the slider main body 215. A rail 219 is provided on the base 201 side, and the guide block 217 is movably engaged with the rail 219.

  According to the above configuration, when the motor 209 is rotated in an appropriate direction, the ball screw 203 rotates in the same direction. Due to the rotation of the ball screw 203, the ball screw nut 211 whose rotation is restricted moves in an appropriate direction. As the ball screw nut 211 moves, the slider 213 also moves in the same direction.

However, the actuator having the above configuration has the following problems.
That is, the actuator converts a rotational motion into a linear motion. At this time, since the natural frequency (f) exists in the ball screw 203, the rotational frequency of the ball member 203 is the natural frequency (f The ball screw 203 will vibrate greatly in the region that coincides with (). The natural frequency (f) is determined by the length and thickness of the ball screw 203, the support state at the end of the ball screw 203, and the like. Therefore, it is necessary to devise such that the rotational speed of the ball screw 203 does not resonate with the natural frequency (f) of the ball screw 203.
By the way, the natural frequency (f) of the shaft is generally obtained by the following equation (I).

L:取付間距雌
E:縦弾性係数
Ｉ:ねじ軸断面の最小二次モーメント
Ａ:ねじ軸断面積
ρ:材料の密度

L: Female spacing
E: Longitudinal elastic modulus I: Minimum secondary moment of screw shaft cross section A: Screw shaft cross section ρ: Material density

  Further, 80% or less of the natural frequency (f) obtained by the above formula (I) is set as the allowable rotational speed (n). For example, consider the mounting state as shown in FIG. In FIG. 8, the same components as those in FIG. 7 are denoted by the same reference numerals. In the case of the mounting state as shown in FIG. 8, the natural frequency (f) becomes the lowest when the distance (B) in the figure becomes the maximum. The allowable rotational speed (n) at that time is as shown in the following formula (II).

λ＝３．９２７
α＝０．８

λ = 3.927
α = 0.8

Thus, by setting the rotation speed of the ball screw 203 to a value that does not resonate with respect to its natural frequency (f), that is, 80% or less of the natural frequency (f), vibration due to resonance is suppressed. be able to.
However, in equations (I) and (II), if the screw shaft cross-sectional area (A) of the ball screw 203 is the same and its length (L) is doubled, the allowable rotational speed (n) is 1/4. This is a problem for speeding up the equipment.

In response to this, by mounting a support in the middle (between the ball nut 211 and the bearing member 207, between the ball nut 211 and the bearing member 205) in the mounting state as shown in FIG. It is considered to increase the number (f) itself and thereby increase the allowable rotational speed (n). An example of such is shown in FIG. In the configuration shown in FIG. 9, an intermediate support 221 is attached on the base 201 and the ball screw 203 is supported by the intermediate support 221. When such an intermediate support 221 is installed, there is a concern about interference with the ball nut 211, the slider 213, and the like that are moved by the rotation of the ball screw 203. Therefore, as shown in FIG. 9, a limit switch 223 is provided, and the limit switch 223 detects the approach of the ball nut 211, the slider 213, and the like that are moved by the rotation of the ball screw 203, whereby the intermediate support 221 is moved. It is configured to retract to the standby position (see Patent Document 1).

Another invention is shown in Patent Document 2. In the structure shown here, a recess in which the support member is moored in advance is formed in the intermediate position, and the support member is positioned in the recess using a spring. And it is the structure which releases a mooring and moves when a slider contact | abuts to a support member.
Patent No. 3221804 JP-A-1-247862 Japanese Patent Laid-Open No. 2-66359 JP-A-6-129510 JP-A-3-14954 JP-A-2-72254 Japanese Utility Model Publication No. 7-7832 Japanese Utility Model Publication No. 6-78659 Japanese Utility Model Publication No. 4-39353

However, in the conventional patent document 1 (Japanese Patent No. 3221804), since the intermediate support is moved by the string body, the string expands and contracts during rapid acceleration and deceleration, and there is a problem of generation of vibration or breakage. there were.
Further, Patent Document 2 (Japanese Patent Laid-Open No. 1-224762) has a problem that the configuration of the apparatus is complicated and large.

  An object of the present invention is to provide an actuator capable of solving the above-mentioned problems of downsizing of the apparatus and generation and breakage of vibration by moving the intermediate support by a rack and pinion mechanism.

In order to solve the above-mentioned problems, the present invention rotationally drives a feed screw shaft rotatably supported at both ends by a pair of bearing members arranged on a base, and feeds the screw into the feed screw shaft. In an actuator configured to fix a nut to a moving body and move the moving body according to a guide rail provided along the feed screw shaft on the base, the moving body and bearing members on both sides thereof are provided. A pair of intermediate supports that receive a radial load of the feed screw shaft and interlock with the moving body in the direction of the feed screw shaft are movably attached to the feed screw shaft, and the movement of the moving body is coupled to a rack and pinion mechanism. It has been transmitted to the intermediate support via.
Further, the present invention provides support brackets that respectively support the intermediate support so as to be movable along the guide rails, connect the support brackets to each other with a connecting rod having a rack surface, and connect to the moving body. The shaft in a direction orthogonal to the feed screw shaft is rotatably mounted, a large gear is provided at one end of the shaft, a small gear is provided at the other end, and the large gear is mounted on a rack provided along the feed screw shaft. The intermediate support is engaged with the moving body within a range in which the small gear is meshed with a rack provided on the connecting rod and the maximum moving distance of the moving body is allowed according to the feed screw shaft. The gear ratio of the large gear and the small gear is set so as to move between the bearing members.

  As an effect of the actuator of the present invention, a feed screw shaft support structure can be obtained with a very simple configuration without complicating the configuration and increasing the size of the apparatus. Then, it is possible to increase the natural frequency of the feed screw shaft, and thus the allowable rotational speed, thereby making it possible to easily cope with high speed and long stroke. Further, by using a rack and pinion mechanism, effects such as long life, rigidity, and acceleration can be obtained.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
1A and 1B are cross-sectional views showing the structure of an actuator according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a state where the table of FIG. 1A has moved leftward.
1A and 1B, reference numeral 1 denotes a feed screw shaft using a ball screw or the like, and 2 denotes a feed screw nut using a ball nut or the like screwed to the feed screw shaft 1. Both ends of the feed screw shaft 1 are rotatably supported by bearing members 5a and 5b respectively attached to two flanges 4a and 4b fixed to the base 3 with a distance L therebetween. One end of the feed screw shaft 1 is connected via a coupling 7 to an output shaft 10a of a motor 10 attached to a plate 6 fixed to the outer surface of the bearing flange 4a.

  As shown in FIG. 3, the feed screw nut 2 is attached by press-fitting a cylindrical base end portion 2a into one end face of a through hole 8a of a table 8 as a moving body through which the feed screw shaft 1 is penetrated. ing. The table 8 is supported on a linear guide 3A disposed on the base 3 in parallel with the feed screw shaft 1 and is stretched between the flanges 4a and 4b between the left and right table surfaces 8A protruding upward. The cover 18 is covered. This linear guide 3A extends in the axial direction and includes a guide rail 9 fixed on the base 3 and a slider 11 fixed on the lower surface of the table 8 movably straddled on the guide rail 9. I have. Ball rolling grooves (not shown) facing each other are arranged on both outer side surfaces of the guide rail 9 and the inner side surface of the slider 11, and a large number of balls are interposed between these ball rolling grooves. It is loaded so that it can roll freely, and the slider 11 moves lightly in the axial direction on the guide rail 9 through the rolling of the ball.

Two sliders 21A and 21B are mounted on the guide rail 9 between the table 8 and the bearing members 5a and 5b.
The brackets 22A and 22B are fixed to the upper surfaces of the two sliders 21A and 21B, and a pair of intermediate supports 20A and 20B that can receive the radial load of the feed screw shaft 1 are rotatable on the brackets 22A and 22B. It is supported. The brackets 22A and 22B are provided with a through hole 22c. The through hole 22c is provided with a slight gap between the inner peripheral surface of the through hole 22c and the outer peripheral surface of the intermediate supports 20A and 20B. Supports 20A and 20B are rotatably supported. The intermediate supports 20A and 20B are provided with flanges 23A and 23B at one end, and the flanges 23A and 23B are fixedly attached to one side of the brackets 22A and 22B.
Retaining rings 17 are attached to the outer peripheral surfaces of the intermediate supports 20A and 20B, and both side walls of the brackets 22A and 22B are sandwiched between the flanges 23A and 23B and the retaining rings 17 and assembled to the brackets 22A and 22B. .
Each intermediate support 20A and 20B is a sliding bearing, and the feed screw shaft 1 is inserted with a slight gap.

  These intermediate supports 20A and 20B are disposed on both sides of the screw nut 2, and are interlocked by fastening the connecting rod 12 and the brackets 22A and 22B with a distance of about L × Z2 / Z1. It is connected. In the width direction of the table 8, a hole 8b in a direction perpendicular to the feed screw shaft 1 is formed, and a shaft 13 is rotatably supported in the hole 8b. A large gear 14 (pitch circle diameter Z1) and a small gear 15 (pitch circle diameter Z2) are fixedly attached to both ends of the shaft 13, and the rack 16 is fixed on the base 1 in parallel with the feed screw shaft 1. And the large gear 14 mesh with each other, and the small gear 15 is disposed so as to mesh with a rack 12 a provided in the longitudinal direction of the connecting rod 12. The intermediate supports 20 </ b> A and 20 </ b> B are configured such that when the table 8 moves, the large gear 14 rotates while meshing with the rack 16, and the rotation of the large gear 14 is transmitted to the small gear 15 via the shaft 13. It is configured to be. The small gear 15 meshes with a rack 12 a provided on the connecting rod 12 and moves the connecting rod 12 by a length corresponding to the rotation of the small gear 15. The connecting rod 12 can be moved in conjunction with the distance moved by the table 8 by Δ2 / Z1 of ΔL. The large gear 14 so that the intermediate supports 20A and 20B move between the table 8 and the bearing members 5a and 5b within a range that allows the maximum movement distance of the table 8 according to the feed screw shaft 1. And the pitch circle diameter ratio Z2 / Z1 of the small gear 15 is set.

Next, the operation of the above embodiment will be described.
When the motor 10 is driven, the feed screw shaft 1 rotates in a predetermined direction as the motor 10 rotates. As a result, the screw nut 2 screwed into the feed screw shaft 1 moves to the left in FIG. 1A, for example, and the table 8 is guided by the linear guide 3A along with this, Move to the left.
At this time, if the distance L between the fulcrums of the feed screw shaft 1 is long, the value of the critical speed u that is inversely proportional to the value of L ² is small, so the feed screw shaft 1 may resonate at a relatively low speed.
However, since the intermediate supports 20A and 20B are provided so as to sandwich the screw nut 2, the distance between the fulcrums (support span) is L / 2 even at the maximum value. As a result, the critical speed is greatly increased to 4 times u, and resonance occurs. It becomes difficult. In this embodiment, the pair of intermediate supports 20 </ b> A and 20 </ b> B is engaged with the rack 16, the large gear 14, and the connecting rod 12 and the small gear 15 through meshing with the movement of the screw nut 2. Interlocking according to the pitch circle diameter ratio Z2 / Z1.

That is, in FIG. 5, the points that divide the distance L between the bearings 5a and 5b on both sides into 1/4 from the right side are P0, P1, P2, P3, and P4.
It is assumed that the screw nut 2 and the intermediate supports 20A and 20B are both at the right end P0 point of the feed screw shaft 1 (FIG. 5A). At this time, the support span is the longest between the left end (point P4) of the feed screw shaft 1 and the intermediate support 20A (point P2), and P2 to P4 = L / 2. From this state, the table 8 moves to the left, and accordingly, the screw gear 2 moves to the left, the large gear 14 rotates along the rack 16, and the small gear 15 rotates along with the rotation of the shaft 13. And the connecting rod 12 moves with the rotation of the small gear 15 to move the intermediate supports 20A and 20B. The intermediate supports 20A and 20B are also in a ratio of ΔL × Z2 / Z1 with respect to the moving amount ΔL of the screw nut 2 by the action of the meshing mechanism of the rack 16 and the large gear 14, and the connecting rod 12 and the small gear 15. Moving. If Z2 / Z1 = 0.5, the intermediate supports 20A and 20B also move at a ratio of 1/2 with respect to the moving amount of the screw nut 2. Therefore, when the screw nut 2 moves L / 4 from the right end and reaches the point P1, the support span a between the bearing 5a on the left end and the intermediate support 20A is a = 3 / 8L. It is shortened from 2 (FIG. 5B).

Further, when the screw nut 2 moves to the left side of L / 4 and reaches the point P2, the intermediate support 20A advances to the left side of L / 8, reaches the position of the point P3, and the support span a is a. = L / 4 (FIG. 5C).
When the screw nut 2 further moves to the left of L / 4 and reaches the point P3 from now on, the intermediate support 20A has advanced to the left of L / 8, and is in the middle position between the points P3 and P4. The span a is reduced to a = L / 8 (FIG. 5 (d)).
Further, when the screw nut 2 further moves to the left of L / 4 and reaches the point P4, the intermediate support 20A has advanced to the left of L / 8 and is at the position of the left end P4. At this time, the support span a is a = 0. On the other hand, the right intermediate support 20B is at the point P2, and the support span d between the right end P0 is the longest L / 2. (FIG. 5 (e)).
Thus, the left support span a gradually decreases with the leftward movement of the screw nut 2 and becomes zero at the left end.On the other hand, the right support span d gradually increases with the leftward movement of the screw nut 2. The maximum is L / 2.

  Next, when the motor 10 is rotated in the opposite direction, the screw nut 2 starts to move to the right in FIG. When the screw nut 2 moves from the left end to the right, the support span d between the bearings 5a, 5b and the intermediate support 20B is continuously reduced in the same manner as the support span a. (FIG. 5 (e) → (a)).

  FIG. 6 shows the change in the support span. The straight line 20a is a reciprocation line of the intermediate support 20A, the straight line 20b is a reciprocation line of the intermediate support 20B, and the straight line L2 is a reciprocation line of the screw nut 2. .

  Further, the present invention is not limited to Z2 / Z1 = 0.5, and in the range of 1> Z2 / Z1 ≦ 0.5, the screw shaft 1 does not resonate from the motor rotation speed to be used and the support span. One of the features is that the intermediate support 20A, 20B can be selected with an efficient value that shortens the moving distance and reduces wear. The intermediate supports 20A and 20B are not limited to sliding bearings, and a screw nut screwed to the feed screw shaft 1 via a ball may be used.

As described above, according to the present invention, the effects listed below can be obtained.
According to the actuator of the present invention, a feed screw shaft support structure can be obtained with a very simple configuration without complicating the configuration and increasing the size of the apparatus. Then, it is possible to increase the natural frequency of the feed screw shaft, and thus the allowable rotational speed, and thereby it is possible to easily cope with high speed and long stroke. When the intermediate support is driven by a pulley as in the prior art (Patent No. 3221804), it is driven by a string, so that the rigidity becomes insufficient and the durability is lost. In the present invention, the rack and pinion mechanism is used. Such effects as long life, rigidity, and high acceleration can be obtained. The present invention is not limited to the above embodiments. For example, the diameter ratio is not limited to Z2 / Z1 = 0.5, and in the range of 1> Z2 / Z1 ≦ 0.5, the screw shaft does not resonate from the motor rotation speed and the support span used, and One of the characteristics is that the intermediate support 20A, 20B can be selected with an efficient value that shortens the moving distance and reduces wear. In each of the above embodiments, a ball screw is used as the feed screw shaft 1 and a ball nut is used as the feed nut 2. However, the present invention is not limited to the ball screw and the ball nut. For example, it is effective when square screws, trapezoidal screws, or the like are used. The same applies to the shape of the support member.

(A) is the longitudinal cross-sectional view by the XX line of FIG.1 (b) which shows the actuator by embodiment of this invention, (b) is the cross-sectional view by the YY line of Fig.1 (a). It is a longitudinal cross-sectional view of the state which moved the table of Fig.1 (a) which shows the actuator by embodiment of this invention to the end. It is a partial expanded sectional view of Fig.1 (a). It is an expanded sectional view of Drawing 1 (b). (a)-(e) is operation | movement explanatory drawing of the screw nut and intermediate | middle support in the actuator of Fig.1 (a). It is a figure showing the change of the relative positional relationship with the motion of the support part of an intermediate | middle support and nut in the actuator of FIG. It is a perspective view which shows the whole structure of the conventional ball screw type moving apparatus. It is a figure for demonstrating the natural frequency while showing the whole structure of the conventional ball screw type moving apparatus. It is a figure which shows the structure which supports the conventional ball screw by an intermediate support.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Feed screw shaft 2 Feed screw nut 3 Base 3A Linear guide 4a, 4b Flange 5a, 5b Bearing member 8 Table (moving body)
9 Guide rail 10 Motor 12 Connecting rod 12a, 16 Rack 13 Shaft 14 Large gear 15 Small gear 17 Retaining ring 18 Cover 20A, 20B Intermediate support 21A, 21B Slider 22A, 22B Bracket

Claims (2)

A feed screw shaft that is rotatably supported at both ends by a pair of bearing members disposed on a base is driven to rotate, and a feed screw nut that is screwed to the feed screw shaft is fixed to the moving body. In the actuator configured to move according to the guide rail provided along the feed screw shaft on the base, the radial load of the feed screw shaft is applied between the movable body and the bearing members on both sides thereof. A pair of intermediate supports that are received and coupled with the moving body in the direction of the feed screw shaft are movably attached to the feed screw shaft, and the movement of the moving body is transmitted to the intermediate support via a rack and a pinion mechanism. Characteristic actuator. Support brackets that respectively support the intermediate support are provided to be movable along the guide rails, the support brackets are connected to each other by a connecting rod having a rack surface, and the moving body is connected to the feed screw shaft. A shaft in an orthogonal direction is rotatably attached, a large gear is provided at one end of the shaft, a small gear is provided at the other end, the large gear is engaged with a rack provided along the feed screw shaft, and the small gear is provided. A gear is meshed with a rack provided on the connecting rod, and the intermediate support moves between the moving body and the bearing member within a range that allows the maximum moving distance of the moving body according to the feed screw shaft. 2. The actuator according to claim 1, wherein a diameter ratio between the large gear and the small gear is set so as to move.

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