JP4251789B2 - Linear actuator - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a linear actuator having a function of converting a rotational motion of the screw nut into a linear motion of the output screw shaft by screwing a screw nut that rotates together with a hollow rotational shaft of a motor portion into an output screw shaft.
[0002]
[Prior art]
FIG. 3 is a longitudinal sectional view showing an example of a conventional linear actuator. In this linear actuator, the motor unit 101 includes a hollow rotary shaft 103, a rotor 105 attached to the small-diameter portion 103 a of the hollow rotary shaft 103, and a stator 107 provided around the rotor 105. The hollow rotating shaft 103 rotates with energization.
[0003]
The hollow rotary shaft 103 has a large-diameter portion 103 b that is rotatably supported by a thrust radial bearing 109. The thrust radial bearing 109 is fastened and fixed by double lock nuts 111 a and 111 b that are screwed onto the outer peripheral surface of the end of the hollow rotary shaft 103 on the large diameter portion 103 b side.
The output screw shaft 113 coaxially penetrates the hollow portion of the hollow rotary shaft 103 and is screwed into a screw nut 115 positioned in the large diameter portion 103 b of the hollow rotary shaft 103.
[0004]
The screw nut 115 has a flange portion 115 a that protrudes radially outward from the opening end on the large-diameter portion 103 b side of the hollow rotary shaft 103, and this flange portion 115 a is connected via a bolt 117 along the axis of the hollow rotary shaft 103. And fixed to the lock nut 111b.
[0005]
According to this linear actuator, since the screw nut 115 rotates integrally with the hollow rotary shaft 103, the output screw shaft 113 screwed into the screw nut 115 linearly moves in the left-right direction in FIG. That is, the rotary motion of the hollow rotary shaft 103 is converted into the linear motion of the output screw shaft 113. Note that the output screw shaft 113 is prevented from rotating about its axis by an appropriate detent means.
[0006]
[Problems to be solved by the invention]
In the conventional linear actuator, the lock nut 111b protrudes from the opening end of the hollow rotary shaft 103 on the large diameter portion 103b side. In other words, the opening end and the flange portion 115a of the screw nut 115 are separated from each other. Therefore, even though the double nuts 111 a and 111 b are used as the lock nut 111, the lock nut 111 is loosened due to the inertial force caused by the rotation of the screw nut 115, and as a result, the thrust bearing 109 In some cases, rattling may occur. If the radial bearing 109 is rattled, noise is generated and smooth rotation of the hollow rotating shaft 103 cannot be expected.
[0007]
In addition, the conventional linear actuator uses the double nuts 111 a and 111 b as the lock nut 111, and thus has a drawback that the total length thereof is increased. Although it is possible to use a lock nut with a lock nut, this lock nut has a large radial dimension, so a space for it must be secured, Expensive.
[0008]
The present invention has been made in view of such circumstances, and provides a linear actuator that can prevent a lock nut for securing a thrust radial bearing from loosening and can be reduced in size and cost. The purpose is that.
[0009]
[Means for Solving the Problems]
The present invention relates to a motor unit having a hollow rotary shaft, an output screw shaft that passes coaxially through the hollow rotary shaft, and screwed with the output screw shaft that is located in the hollow rotary shaft. And a screw nut provided with a flange portion protruding radially outward from one open end of the hollow rotary shaft, and a thrust radial bearing for supporting the hollow rotary shaft on the one open end side, A linear bearing in which a thrust radial bearing is fixed by a tightening force of a lock nut screwed to an outer peripheral surface on one opening end side of the hollow rotary shaft, and a flange portion of the screw nut is fixed to the lock nut by a bolt. An actuator, wherein a flange portion of the screw nut is brought into contact with one open end of the hollow rotary shaft, and the flange portion and the lock nut Having a structure in which a space between.
[0010]
According to the present invention, the tightening force of the bolt acts in the direction in which the space between the flange portion of the screw nut and the lock nut is compressed, that is, in the direction in which the flange portion and the lock nut attract each other. Therefore, the flange portion is extremely pressed against the opening end of the large-diameter portion of the rotating shaft, and a force in the direction along the axis acts on the lock nut.
[0011]
The flange portion of the screw nut may be screwed to the main body portion of the screw nut.
A ball screw shaft may be used as the output screw shaft, and a ball screw nut may be used as the screw nut.
Furthermore, a sliding screw shaft can be used as the output screw shaft, and a sliding screw nut can be used as the screw nut.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows an embodiment of a linear actuator according to the present invention. In this linear actuator, the motor unit 1 includes a hollow rotating shaft 3, a rotor 5 integrally formed on the outer peripheral surface of the rotating shaft 3, and a stator 7 provided around the rotor 5. Yes.
[0013]
The hollow rotary shaft 3 has a small diameter portion 3 a supported by a bearing 4 and a large diameter portion 3 b supported by a thrust radial bearing 9. The inner side of the thrust radial bearing 9 is fastened and fixed to the outer peripheral surface of the end portion by a lock nut 11 screwed to the outer peripheral surface of the end portion of the hollow rotary shaft 3 on the large diameter portion 3b side.
Since the motor unit 1 has the above-described configuration, the hollow rotating shaft 3 rotates with energization.
[0014]
The hollow rotating shaft 3 coaxially penetrates the output screw shaft 13 into the hollow portion, and a screw nut 15 is coaxially inserted into the large-diameter hollow portion and screwed into the output screw shaft 13. I'm allowed. The screw nut 15 has a flange portion 15 a that protrudes radially outward from the open end of the rotary shaft 3 on the large diameter portion 3 b side, and the flange portion 15 a is connected to the lock nut via a bolt 17 along the axis of the rotary shaft 3. 11 is fixed. Therefore, the screw nut 15 can rotate together with the hollow rotating shaft 3.
[0015]
Since the output screw shaft 13 is prevented from rotating around its axis by an appropriate detent means, the output screw shaft 13 linearly moves in the left-right direction in FIG. That is, according to this actuator, the rotary motion of the hollow rotary shaft 3 is converted into the linear motion of the output screw shaft 13.
[0016]
By the way, in this linear actuator having the above-described configuration, the end surface of the lock nut 11 on the side opposite to the thrust radial bearing 9 side is positioned closer to the thrust bearing 9 side than the opening end of the rotary shaft 3 on the large diameter portion 3b side. is doing. Further, the portion of the screw nut 15 excluding the flange portion 15 a is in a state of being accommodated in the large diameter portion 3 b of the rotating shaft 3.
Therefore, when the flange portion 15a of the screw nut 15 is fastened to the lock nut 11 with the bolt 17, an annular gap 19 is formed between the flange portion 15a and the lock nut 11, and the flange portion 15a is larger than the rotary shaft 3. It will be press-contacted to the opening end by the side of the diameter part 3b.
[0017]
The tightening force of the bolt 17 acts in a direction in which the gap is compressed, that is, in a direction in which the flange portion 15a and the lock nut 11 are attracted to each other. Therefore, the flange portion 15a is extremely pressed against the opening end of the large diameter portion 3b, and a force in the direction along the axis acts on the lock nut. As a result, the lock based on the inertial force of the screw nut 15 is achieved. The loosening of the nut 11 is prevented. In addition, since a compression reaction force acts on the bolt 17, loosening of the bolt 17 is also prevented.
[0018]
As described above, according to the linear actuator of this embodiment, it is possible to reliably prevent the lock nut from being loosened which could not be prevented even when a double lock nut or a locking nut is used. In addition, since an expensive and large double lock nut or locking nut is not required, the cost can be reduced and the size can be reduced.
[0019]
When a ball screw shaft is used as the output screw shaft 13, a ball screw nut is used as the screw nut 15. When a sliding screw shaft is used as the output screw shaft 13, a sliding screw nut is used as the screw nut 15. used.
[0020]
The screw nut 15 used in the actuator has a main body portion 15a and a flange portion 15a integrally formed. As shown in FIG. 2, the screw nut 15 having a configuration in which the flange portion 15a is fixed to the main body portion 15a by a bolt 21. Even when ′ is used, the present invention is effective.
[0021]
【The invention's effect】
According to the present invention, the flange portion of the screw nut is brought into contact with one open end of the hollow rotary shaft of the motor portion, and a space is provided between the lock nut that locks the thrust radial bearing and the flange portion. Since it has the structure, the tightening force of the bolt for fixing the flange to the lock nut acts in the direction in which the space is compressed, that is, the direction in which the flange portion and the lock nut attract each other.
As a result, the flange portion is pressed extremely strongly against the opening end of the large-diameter portion of the rotary shaft, and a force in the direction along the axis acts on the lock nut, so that the lock nut is loosened based on the inertial force of the screw nut. Is prevented. Further, since the reaction force accompanying the compression of the space acts on the bolt, loosening of the bolt is also prevented.
In addition, according to the present invention, an expensive and large-sized double lock nut or a locking nut is not required, so that the cost can be reduced and the size can be reduced.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view showing an embodiment of a linear actuator according to the present invention.
FIG. 2 is a longitudinal sectional view showing a linear actuator according to the present invention having a screw nut with a flange portion formed separately from a main body portion.
FIG. 3 is a longitudinal sectional view showing the structure of a conventional linear actuator.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Motor part 3 Hollow rotating shaft 3a Small diameter part 3b Large diameter part 5 Rotor 7 Stator 9 Thrust radial bearing 11 Lock nut 13 Output screw shaft 15, 15 'Screw nut 17 Bolt 19 Clearance 20 Bolt

Claims (4)

A motor portion having a hollow rotary shaft; an output screw shaft coaxially passing through the hollow rotary shaft; and being screwed into the output screw shaft located in the hollow rotary shaft; A screw nut provided with a flange projecting radially outward from one open end of the cylindrical rotary shaft, and a thrust radial bearing for supporting the hollow rotary shaft on the one open end side,
The thrust bearing is fixed by a fastening force of a lock nut that is screwed to the outer peripheral surface of one open end of the hollow rotary shaft, and is a bolt along the hollow rotary shaft that is passed through the flange portion of the screw nut. Is a linear actuator that is screwed into the lock nut to fix the flange portion to the lock nut,
A linear actuator, wherein a flange portion of the screw nut is brought into contact with one open end of the hollow rotary shaft, and a space is provided between the flange portion and the lock nut.   The linear actuator according to claim 1, wherein a flange portion of the screw nut is screwed to a main body portion of the screw nut.   3. The linear actuator according to claim 1, wherein the output screw shaft is a ball screw shaft, and the screw nut is a ball screw nut.   The linear actuator according to claim 1, wherein the output screw shaft is a sliding screw shaft, and the screw nut is a sliding screw nut.

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