JPH0888953A - Actuator - Google Patents

Abstract

PURPOSE: To prevent the deflection by arranging constitution such that the load on a bearing means is transmitted directly to a housing arranged at the periphery not through the stator of an AC servomotor, and that any one bearing is fixed in axial direction and the other is free in axial direction. CONSTITUTION: At the positions of bearings 25 and 27, the load of an output shaft 13 is transmitted to a housing 1 through a bearing holding means 21, and at the position of the bearing 35 it is transmitted to the housing 1 through a flange member 33. Especially, in the transmission course through the flange member 33, a gap is provided between the stator 9 and the housing 1. In short, the load of the output shaft 13 never works on the stator 9 directly. Furthermore, the bearing 35 is attached shiftably in axial direction, within the range of elastic transformation of a plate spring 37, so it can absorb the shifting in axial direction of the output shaft 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an actuator, and more particularly, to a component of an AC servo motor in which a ball screw and an AC servo motor integrated with the output shaft of the AC servo motor are used. The present invention relates to a stator (stator) that is designed so as not to be overloaded.

[0002]

2. Description of the Related Art An actuator, for example, a uniaxial actuator has a structure as shown in FIG. First,
There is an AC servo motor 101, and a ball screw 107 is connected to an output shaft 103 of the AC servo motor 101 via a coupling 105. A ball nut 109 is screwed onto the ball screw 107, and a slider 111 is attached to the ball nut 109. Then, by rotating the AC servo motor 101 in an appropriate direction, the output shaft 103, the coupling 10
5. The ball screw 107 rotates in the same direction. Then, the ball nut 109, the rotation of which is restricted, moves in an appropriate direction, which causes the slider 111 to move in the same direction. The AC servomotor 101 is composed of a stator (stator) 101a and a rotor (rotor) 101b fixed to the output shaft 103. or,
The output shaft 103 is axially supported by bearings 113, 115, 117 on both sides of the AC servo motor 101. The ball screw 107 is pivotally supported by bearings 119, 121, 123 on both sides of the ball nut 109. In addition, the anti-AC servomotor 10 of the bearing 117
A detection unit (for example, an optical detection unit, a magnetic detection unit, etc.) 125 that detects the amount of rotation of the AC servo motor 101 is attached to the first side. It should be noted that any device such as a gripping device or a welding robot is mounted on the slider 111.

In the actuator having the above structure, the output shaft 103 of the AC servomotor 101 and the ball screw 107 are connected through the coupling 105, so that the number of parts is large and the assembling work is difficult. In addition, there is a problem that the device becomes large. Further, since the coupling 105 is used for connection, there is a problem that the rigidity is lowered in the integrated state. Furthermore, the output shaft 10 of the AC servo motor 101 is also problematic.
3 and the ball screw 107 may be misaligned with each other, which may impair highly accurate control.

In view of these problems, it has been considered that the output shaft of the AC servo motor and the ball screw are integrated beforehand to form a ball screw integrated AC servo motor. As such, for example, the actual Kaihei 1-86
457, JP-A-1-252339, and JP-A-6-86501. In all of these, the output shaft of the AC servomotor and the ball screw are integrated in advance, thereby eliminating the problem when the coupling structure using the coupling as described above is adopted. Reduce the number of parts to facilitate the assembly work and reduce the size of the device.
This is intended to improve control accuracy.

An example of such a device is shown in FIG. still,
The same parts as those shown in FIG. 6 are designated by the same reference numerals and the description thereof will be omitted. In this case, since the output shaft 103 of the AC servomotor 101 and the ball screw 107 are integrally formed in advance, the coupling 105 is not required unlike the one having the configuration shown in FIG. It is possible to solve the problem when the ring 105 is used.

[0006]

The above-mentioned conventional structure has the following problems. That is, in the case of the ball screw integrated type AC servo motor, the AC servo motor 10
1, the output shaft 103 and the ball screw 107 are extended with a relatively long span. In such a structure, the shaft is variously deformed. For example, the screw shaft itself may be deformed due to an error in manufacturing or assembly, or may be sagging due to its own weight. This type of deformation causes a large "blur" due to centrifugal forces on shafts that rotate at high speeds. Especially, in a region where the rotation speed of the shaft is close to the resonance frequency of the shaft, the “blur” becomes extremely large. Such load, error, and displacement due to resonance change the distance between the stator 101a and the rotor 101b, and impair the soundness of the AC servomotor 101 against torque generation. Further, the AC servo motor 101 is provided with a detecting means 125 for detecting the amount of rotation thereof. For example, a disk having a slit rotates and the slit is detected by an optical detecting means or the like. By doing so, the rotation amount of the AC servo motor 101 is detected. However, if the above-mentioned "blur" occurs, the positional relationship between the slit and the optical detection means or the like is lost, and there is a problem that normal detection cannot be performed. It is possible to add another shaft support in the vicinity of the detection unit to suppress "blur", but in this case, in order to equalize the torque generated by the motor, the coaxiality between the rotor 101b and the stator 101a should be matched. Structural consideration is required. In addition, a reaction force is generated in the added shaft support in order to suppress "blur", but it is necessary to prevent the reaction force from acting as a shearing force on the laminated steel plates of the stator 101a. Further, in the mechanism in which the ball screw 107 and the output shaft 103 of the AC servo motor 101 are integrated, the mechanism expands due to heat generated by the operation. It is necessary to consider that the displacement due to this expansion will impair the positional relationship of the detection means 125 and prevent normal detection. In the above-mentioned Japanese Utility Model Laid-Open No. 1-86457, Japanese Patent Laid-Open No. 1-252339, and Japanese Patent Laid-Open No. 6-86501, although there is a description about the ball screw integrated AC servo motor having the configuration shown in FIG. 7, There is no reference to the above-mentioned problems, that is, the above-mentioned problems have not been solved, and therefore, the ball screw integrated AC servomotor has not yet been implemented.

The present invention has been made on the basis of such a point, and an object of the present invention is, on the premise of a ball screw integrated servo motor, to cause the above-mentioned "blur" and various problems resulting therefrom. It is to provide an actuator that can be eliminated.

[0008]

In order to achieve the above object, an actuator according to the present invention rotates a ball screw which is previously extended as an integral body with an output shaft of an AC servomotor by an AC servomotor composed of a stator and a rotor. In an actuator in which a slider is moved via a ball nut screwed to a ball screw in a state where its rotation is regulated, output shafts are supported by bearing means on both sides of the AC servomotor, respectively. The load applied to each bearing means is directly transmitted to the housing arranged on the outer circumference without passing through the stator of the AC servomotor, and one of the bearing means is fixed in the axial direction and the other is fixed in the axial direction. It is characterized by being free. At this time, the output shaft penetrates the AC servomotor and is projected and arranged on the opposite side of the ball screw by a predetermined amount, and there is provided a detection means for detecting the rotation amount of the AC servomotor. It is conceivable that one bearing means is provided between the means and the AC servomotor. Further, the output shaft penetrates the AC servomotor and is projected / arranged by a predetermined amount on the opposite side of the ball screw, and there is provided detection means for detecting the rotation amount of the AC servomotor. One bearing means may be provided on the side opposite to the AC servo motor. Further, it is conceivable that the bearing means arranged on the ball screw side of the AC servomotor is fixed in the axial direction and the bearing means arranged on the detecting means side is free in the axial direction. Further, it is conceivable that the bearing means arranged on the detecting means side of the AC servomotor is fixed in the axial direction and the bearing means arranged on the ball screw side is free in the axial direction. Further, it is conceivable that the bearing means which is free in the axial direction is movable in the axial direction within the range of elastic deformation of the elastic member that is pressed and arranged. Further, it may be considered that the stator of the AC servomotor is attached / fixed to the housing with a screw. or,
It is conceivable to mount and fix the stator on a mounting seat provided in the housing with screws to provide a gap between the outer circumference of the stator and the housing.

[0009]

That is, in the actuator using the AC servo motor integrated with a ball screw, the AC servo motor is sandwiched so that both sides are axially supported by the bearing means, and at the same time, the load is prevented from directly acting on the stator of the AC servo motor. It is attached so as to be transmitted to a housing arranged on the outer periphery of the AC servomotor. As a result, “vibration” of the stator and rotor of the AC servo motor and the detection unit can be prevented, and the soundness of the AC servo motor and the soundness of the detection mechanism can be ensured. Further, in this configuration, the shaft supports on both sides of the AC servo motor are independent of the stator, and the coaxiality is not deteriorated due to the occurrence of accumulated errors due to the fitting with the stator. Further, this structure prevents the action of shearing force on the stator and maintains its soundness. Also, one bearing means is fixed in the axial direction, and it is long so that the displacement of the ball screw, which is likely to thermally expand, does not spread to the detection side, and the other is free to absorb various displacements.
It is designed to absorb the assembly error. Further, the output shaft penetrates the AC servomotor and is projected / arranged by a predetermined amount on the opposite side of the ball screw, and there is provided detection means for detecting the rotation amount of the AC servomotor. It is conceivable that one bearing means is provided between the AC servo motor and the AC servo motor. In this case, since the support is provided immediately before the detection means, the influence of the shake on the detection means is greatly reduced. Can be reduced. Further, the output shaft penetrates the AC servomotor and is projected / arranged by a predetermined amount on the opposite side of the ball screw, and there is provided detection means for detecting the rotation amount of the AC servomotor. It is conceivable that one of the bearing means is provided on the side opposite to the AC servo motor, and in this case, the support is further strengthened, and the influence of the shake on the detection means can be further reduced. it can. Further, it is conceivable that the stator of the AC servomotor is mounted / fixed to the housing with screws, whereby the mounting structure of the stator can be made stronger and the influence of the load can be greatly reduced. Further, it is considered that the stator is mounted and fixed to the mounting seat provided in the housing with a screw to provide a gap between the outer periphery of the stator and the housing. In this case, the load is temporarily transmitted to the housing. However, the presence of the gap significantly reduces the influence on the stator.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The first embodiment of the present invention will be described below with reference to FIGS.
An example will be described. The figure shows a part of the actuator according to the present embodiment (configuration on the AC servomotor side). First, there is a housing 1 on the AC servomotor side,
A cap 3 is attached to the right end of the housing 1 in the figure. Further, on the left side of the housing 1 in the drawing, another housing 5 for accommodating the moving mechanism part of the actuator
Is installed. An AC servomotor 7 is housed and arranged in the housing 1. The AC servomotor 7 is composed of a stator (stator) 9 mounted on the housing 1 side and a rotor (rotor) 11 rotatably arranged on the inner peripheral side of the stator 9. The stator 9 includes a stator body 9a made of laminated steel plates, a coil 9b, and the like.
Are fixed to the housing 1 by bolts 10 in a direction parallel to the screw axis. The rotor 11 includes a rotor body 11a and a magnet 11 attracted and fixed to the outer periphery of the rotor body 11a.
b and.

An output shaft 13 of the AC servomotor 7 is arranged on the inner peripheral side of the rotor 11, and the output shaft 13 is provided.
Are fixed to the rotor 11 by a key / key groove structure. The output shaft 13 is a ball screw integrated output shaft, and as shown in the drawing, a ball screw 15 is provided in a predetermined range on the left side of the drawing. A ball nut 17 is screwed onto the ball screw 15, and a slider 19 is fixed to the ball nut 17. Therefore, A
By rotating and driving the C servo motor 7 in an appropriate direction, the ball screw 15 rotates in the same direction, whereby the ball nut 17 whose rotation is restricted and the slider 19 fixed thereto are moved in an appropriate direction. It will move (either left or right in the figure).

Next, the ball screw integrated type output shaft 13
Will be described. First, a flange portion 1a is provided on the left end of the housing 1 in the figure, and a bearing holding member 21 is arranged on the inner peripheral side of the flange portion 1a. The bearing holding member 21 is composed of a flange portion 21a and a cylindrical portion 21b, and an engaging portion 21c is provided on the inner peripheral surface of the cylindrical portion 21b at the right end in the drawing. Further, the bearing holding member 21 is provided with a plurality of (four in this embodiment) fixing bolts 23 via the flange portion 21a, and the flange portion 1a of the housing 1 is secured.
It is designed to be fixed to.

The cylindrical portion 21 of the bearing holding member 21.
Bearings 25 and 27 forming one bearing means are arranged on the inner peripheral side of b so as to support the output shaft 13. Further, a bearing holding member 29 is provided, and the bearing holding member 29 is fixed to the left side of the bearing holding member 21 in the drawing by a plurality of (four in this embodiment) fixing bolts 31, so that The bearings 25 and 27 are fixed between the bearings 25 and 27. In other words, the outer rings of the two bearings 25 and 27 are attached with their movements restricted in the axial direction. Also, the bearing 25,
The inner ring of 27 is a ball screw 15 provided on the output shaft 13.
The output shaft 13 is fixed to the shoulder of the output shaft 13 via the sleeve 24, the rotor 11, and the washer 53 by the nut 51, and the movement of the output shaft 13 is restricted in the axial direction.

On the other hand, on the right side of the AC servomotor 11 in the figure, a flange member 33 which is a member separate from the housing 1 is provided.
Is arranged. The housing 33 has a cylindrical portion 33.
a, and the locking portion 33 is provided at the right end of the cylindrical portion 33a in the figure.
b is projected. A bearing 35 as the other bearing means is arranged in the cylindrical portion 33a to support the output shaft 13. The bearing 35
A leaf spring 37 as an elastic member is inserted between the locking portion 33b and the locking portion 33b so as to constantly urge the bearing 35 to the left side in the drawing. That is, the bearing 35
Is sandwiched by the stepped portion 13a of the output shaft 13 and the leaf spring 37 so as to be movable in the axial direction within the range of elastic deformation of the leaf spring 37.

The tip of the output shaft 13 extends to the right side of the bearing 35 in the figure, and a detecting means 39 is provided there. That is, a disc mounting hub 41 is screwed onto the tip of the output shaft 13, and a disc 43 having a slit is attached to the disc mounting hub 41. or,
Sensors 45 and 47 are arranged at the outer peripheral positions of the disc 43, respectively. By optically detecting the slit of the disc 43 by these sensors 45 and 47,
The rotation amount of the output shaft 13, that is, the AC servomotor 7 is detected.

The end of the output shaft 13 on the ball screw 15 side is supported by a bearing (not shown). That is, in the present embodiment, the output shaft 13 integrated with the ball screw is used.
Will be pivotally supported at 3 points.

The operation and effect will be described based on the above configuration. Since the basic operation of the actuator is as described above, the operation of the support structure of the output shaft 13 integrated with the ball screw will be described here. First, the output shaft 13 is axially supported at three positions in the longitudinal direction. That is, support by a bearing (not shown) arranged at the left end in the drawing, support by bearings 25 and 27 at the left end in the drawing in the housing 1, A
This is the support by the bearing 35 on the right side of the C servo motor 7 in the figure. By the support at these three points, the support rigidity of the output shaft 13 can be increased and the "blur" of the shaft center can be suppressed. In particular, since the bearing is supported on the right side of the AC servomotor 7 in the drawing, it is possible to effectively suppress the “blur” of the shaft center of the output shaft 13 on the detection means 39 side. Thereby,
The relative positional relationship between the disc 43 of the detection means 39 and the sensors 45 and 47 does not shift, and it is possible to always perform highly accurate detection.

Next, the load that acts on the AC servomotor 7, in particular, on the stator 9 that is a component thereof will be described. For example, in the structure in which the AC servo motor 7 is similarly axially supported via the stator 9, by supporting the output shaft 13,
A shearing force acts on the output shaft 13. Then, the shearing force directly acts on the stator 9 of the AC servomotor 7. In this regard, in the present embodiment, if any load acts on the output shaft 13, the load is
The flange member 3 is transmitted to the housing 1 via the bearings 25 and 27 and is also transmitted via the bearing 35.
3, transmitted to the housing 1. This will be described in more detail. First, at the positions of the bearings 25 and 27, the load is transmitted from there to the housing 1 via the bearing holding member 21, and does not directly act on the stator 9. Further, at the position of the bearing 35, it is transmitted to the housing 1 via the flange member 33, and the load does not directly act on the stator 9 also here. In other words, even if some load acts on the output shaft 13, it does not directly act on the stator 9, and therefore the position of the stator 9 shifts and the relative position with respect to the rotor 11 changes, and the AC servomotor 7 There is no loss of sound behavior. In particular, in the transmission path via the bearing 35 and the flange member 33, as shown in FIG. 1, a gap is provided between the stator 9 and the housing 1, so that the load acts temporarily. However, as described above, not only does it not directly act on the stator 9, but even if a load is transmitted to the housing 1, the probability that it will act on the stator 9 is extremely low.

Next, the operation associated with the degree of freedom of the bearing 35 in the axial direction will be described. As described above, the bearing 35 is attached so as to be movable in the axial direction within the range of elastic deformation of the leaf spring 37. Therefore, even if the output shaft 13 moves in the axial direction for some reason, it can be effectively absorbed. or,
Even if there is a dimensional error or the like of each component, even if the mounting position of each component in the axial direction shifts due to it, it can be absorbed. In addition, since the output shaft 13 has three-point support having the above-described structure, the output shaft 13 is supported more firmly, and thereby the number of rotations can be increased. This means speeding up as an actuator.

Next, a second embodiment of the present invention will be described with reference to FIG. In the case of this embodiment, the construction is basically the same as that of the first embodiment, but since the construction is partially different, only that portion will be explained. First, a bearing holding member that holds the bearings 25 and 27 is integrated with the housing 1. A shim ring 61 and a wave washer 63 are used instead of the leaf spring. Also, bearing 2
Nos. 5 and 27 are nuts 51 screwed to the output shaft 13 without a rotor, and the rotor and the output shaft 13 are not keyed but bonded or knurled.
It is fixed together with the sleeve. The other structure is substantially the same as that of the first embodiment, and therefore, the same operation and effect as those of the first embodiment can be obtained.

Next, a third embodiment of the present invention will be described with reference to FIG. In the case of this embodiment, the bearing 35 is arranged on the right side of the detection means 39 in the figure, thereby further reducing the influence of the “blur” of the output shaft 13 on the detection means 39. Therefore, the same effects as those of the first and second embodiments can be obtained, and as described above, the influence of the “blur” of the output shaft 13 on the detecting means 39 can be further reduced. . In FIG. 4, the ball screw 15 of the output shaft 13
A bearing 65 is shown pivotally supporting the side end.

Next, a fourth embodiment of the present invention will be described with reference to FIG. In the case of this embodiment, first, one bearing (bearing 2
5), and two bearings (bearing 27, bearing 35) on the right side of the AC servomotor 7 in the figure. Other configurations are the same as those in the first and second embodiments. Therefore, it is possible to obtain the same effects as those of the first and second embodiments.

The present invention is not limited to the first to fourth embodiments. First, the basic structure of the actuator is not limited to that shown in the drawings. Further, the number of bearings to be used in each bearing means may be arbitrarily set.

[0024]

As described in detail above, according to the actuator of the present invention, in an actuator using an AC servomotor integrated with a ball screw, it is possible to effectively reduce "blur" of the output shaft integrally provided with the ball screw. Even if a “blur” occurs, it is possible to prevent the detection performance of the detection means from being impaired. In addition, since the load is configured to act on the housing entirely, the load does not directly act on the stator of the AC servo motor, and the soundness of the AC servo motor can be maintained. The reliability of the actuator can be significantly improved, and the device can be easily downsized.

[Brief description of drawings]

FIG. 1 is a sectional view showing a configuration of a part of an actuator in a diagram showing a first embodiment of the present invention.

FIG. 2 is a view showing a first embodiment of the present invention, and is a sectional view taken along the line II-II of FIG.

FIG. 3 is a sectional view showing a structure of a part of an actuator in a diagram showing a second embodiment of the present invention.

FIG. 4 is a sectional view showing a structure of a part of an actuator in a view showing a third embodiment of the present invention.

FIG. 5 is a cross-sectional view showing a part of the structure of the actuator according to the fourth embodiment of the present invention.

FIG. 6 is a cross-sectional view showing a structure of an actuator in a conventional example.

FIG. 7 is a cross-sectional view showing a configuration of an actuator in a conventional example.

[Explanation of symbols]

 1 Housing 3 Cap 5 Housing 7 AC Servo Motor 9 Stator (Stator) 11 Rotor (Rotor) 13 Output Shaft 15 Ball Screw 17 Ball Nut 19 Slider 21 Flange Part of Housing 1 23 Fixing Bolt 25 Bearing 27 Bearing 31 Fixing Bolt 33 Flange Member 35 Bearing 39 Detection means

Claims (8)

[Claims] 1. A ball nut which is rotated by an AC servomotor composed of a stator and a rotor and which is previously extended as an integral body with the output shaft of the AC servomotor, and is screwed onto the ball screw in a state where its rotation is restricted. In the actuator in which the slider is moved through the shafts, the output shafts are respectively supported by bearing means on both sides of the AC servomotor, and the load applied to each bearing means is passed through the stator of the AC servomotor. An actuator characterized in that it is configured to be transmitted to a housing arranged on the outer periphery of an AC servomotor without any movement, and one of the bearing means is fixed in the axial direction and the other is free in the axial direction. 2. The actuator according to claim 1, wherein the output shaft penetrates the AC servomotor and is projected and arranged by a predetermined amount on the opposite side of the ball screw, and the output shaft has an A
An actuator characterized in that detection means for detecting the amount of rotation of the C servo motor is provided, and one bearing means is provided between the detection means and the AC servo motor. 3. The actuator according to claim 1, wherein the output shaft penetrates the AC servomotor and is protruded and arranged on a side opposite to the ball screw by a predetermined amount, and the output shaft A
An actuator characterized in that detection means for detecting the rotation amount of the C servo motor is provided, and one bearing means is provided on the side opposite to the AC servo motor of the detection means. 4. The actuator according to claim 2 or 3, wherein the bearing means arranged on the ball screw side of the AC servomotor is fixed in the axial direction, and the bearing means arranged on the detecting means side is free in the axial direction. The actuator characterized in that 5. The actuator according to claim 2 or 3, wherein the bearing means arranged on the detection means side of the AC servomotor is fixed in the axial direction, and the bearing means arranged on the ball screw side is free in the axial direction. The actuator characterized in that 6. The actuator according to claim 1, claim 2, claim 3, claim 4, or claim 5,
An actuator characterized in that the bearing means which is free in the axial direction is movable in the axial direction within the range of elastic deformation of the elastic member that is press-contacted and arranged. 7. The actuator according to claim 1, 2 or 3, or 4 or 5 or 6, wherein the stator of the AC servomotor is attached / fixed to the housing with a screw. Actuator characterized by being present. 8. The actuator according to claim 7, wherein the stator is attached / fixed to a mounting seat provided in the housing with a screw, and a gap is formed between the outer periphery of the stator and the housing. Characteristic actuator.