JP2002372118A - Linear actuator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a linear actuator allowing use of a large-sized rotor for a motor and a screw nut. SOLUTION: This linear actuator is provided with a motor part 1 having a hollow rotary shaft 3, a screw shaft 13 for output coaxially passing through the hollow rotary shaft 3 and a screw nut 15 which is arranged within the hollow rotary shaft 3 and is screwed onto the screw shaft 13 for output. A rotary motion of the hollow rotary shaft 3 is converted into a linear motion of the screw shaft 13 for output via the screw nut I5. The hollow rotary shaft 3 has a stepped structure having a small diameter part 3a and a large diameter part 3b. The rotor of the motor part 1 is mounted on the small diameter part 3a. The screw nut 15 is disposed within the large diameter part 3b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a linear actuator for converting a rotary motion of a motor unit into a linear motion and outputting the linear motion.

[0002]

2. Description of the Related 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.
And a rotor 105 mounted on the outer periphery of the hollow rotary shaft 103, and a stator 107 provided around the rotor 105. The hollow rotary shaft 103 rotates with the energization. I do.

[0003] The hollow rotary shaft 103 has a straight pipe shape,
The left end in the figure is supported by a normal bearing 104, and the right end is supported by a thrust radial bearing 109. Note that the inner of the thrust radial bearing 109 is the hollow rotary shaft 103.
Is locked to the rotation shaft 103 by a lock nut member 111 screwed to the outer periphery of the rotation shaft 103.

[0004] The output screw shaft 113 is connected to the hollow rotary shaft 10.
3 coaxially penetrates the hollow rotary shaft 103.
Is screwed into a screw nut 115 located in the right side end of the screw. The screw nut 115 has a flange portion 115a that protrudes radially outward from an opening end on the right side of the hollow rotary shaft 103.
And the flange portion 115a is fixed to the flange portion 111a of the lock nut member 111.

According to this linear actuator, since the screw nut 115 rotates integrally with the hollow rotary shaft 103, the output screw shaft 11 screwed to the screw nut 115.
3 moves linearly in the horizontal direction in the figure. That is, the rotational motion of the hollow rotary shaft 103 is converted into a linear motion of the output screw shaft 113. The output screw shaft 113 is prevented from rotating about its axis by a suitable rotation preventing means.

[0006]

The above-described conventional linear actuator has the following problems because the hollow rotary shaft 103 has a uniform inner diameter over the entire length thereof. a) If the diameter of the hollow rotating shaft 103 is reduced so that the rotor 105 has a sufficiently large shape, a small-sized screw nut 15 having a low load-bearing strength must be used. b) Conversely, if the diameter of the hollow rotary shaft 103 is set to be large in order to use a large-sized screw nut 15 having a high load-bearing strength, the shape of the core, magnet, and the like constituting the rotor 105 is restricted. In addition, the characteristics of the motor unit 101 deteriorate.

The present invention has been made in view of such circumstances, and has as its object to provide a linear actuator which can use a rotor and a screw nut having a large shape.

[0008]

According to the present invention, there is provided a motor having a hollow rotary shaft, an output screw shaft coaxially penetrating the hollow rotary shaft, and a motor disposed inside the hollow rotary shaft. A linear actuator comprising a screw nut screwed with the output screw shaft, wherein the linear actuator is configured to convert a rotational motion of the hollow rotary shaft into a linear motion of the output screw shaft via the screw nut. The rotary shaft has a stepped structure having a small-diameter portion and a large-diameter portion, and a rotor of the motor unit is mounted on the small-diameter portion, and the screw nut is disposed in the large-diameter portion. According to the present invention,
The shape of the rotor can be set as large as possible, and the degree of freedom in selecting the shape of the screw nut can be increased.

It is preferable that the hollow rotary shaft is supported by a plurality of thrust radial bearings at a portion where the screw nut is provided, in order to suppress vibration of the screw nut. The rotor of the motor unit can be positioned by a stepped portion existing at a boundary between the small diameter portion and the large diameter portion of the hollow rotary shaft. This makes it possible to position the rotor without providing any special positioning means. If the end of the small-diameter portion of the hollow rotary shaft is extended and a component of a rotation sensor and / or a component of a brake is added to the extended portion, the moving speed and position of the output screw shaft can be reduced. The detection function and / or the braking function of the screw shaft can be realized with a compact configuration.

[0010]

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 rotary shaft 3.
And a rotor 5 attached to the outer peripheral surface of the rotating shaft 3, and a stator 7 provided around the rotor 5.

The hollow rotary shaft 3 has a stepped structure including a small-diameter portion 3a supported by a bearing 4 and a large-diameter portion 3b supported by a thrust radial bearing 9 receiving both a thrust load and a radial load. The rotor 5 is mounted on the small diameter portion 3a, and a screw nut 15 described later is disposed in the large diameter portion 3b. The inner surface of the bearing 9 is fixed to the large-diameter portion 3b by a lock nut 11 screwed to the outer peripheral surface of the end of the large-diameter portion 3b. Since the motor unit 1 has the above-described configuration, the hollow rotary shaft 3 rotates together with the rotor 5 in accordance with the energization of a stator winding (not shown).

An output screw shaft 13 is coaxially penetrated through the hollow portion of the hollow rotary shaft 3, and the output screw shaft 13 is screwed into the large diameter portion 3 b of the rotary shaft 3. The combined screw nut 15 is inserted. Screw nut 15
The rotary shaft 3 has a flange portion 15a that protrudes radially outward from the opening end on the large diameter portion 3b side, and the flange portion 15a is fixed to the lock nut 11 via a bolt 17. Therefore, the screw nut 15 can rotate together with the hollow rotary shaft 3.

Since the output screw shaft 13 is prevented from rotating about its axis by a suitable detent means, it moves linearly in the left-right direction in FIG. That is, according to this actuator, the rotational movement of the hollow rotary shaft 3 is controlled by the output screw shaft 13.
Is converted to linear motion.

As described above, the linear actuator according to this embodiment has a stepped structure in which the hollow rotary shaft 3 has the small-diameter portion 3a and the large-diameter portion 3b.
The rotor 3 of the motor unit 1 is attached to the
Since the screw nut 15 is arranged in b,
The following advantages are obtained.

That is, the small diameter portion 3a is connected to the screw shaft 1 for output.
3 can be set as small as possible within a range that does not impede the linear motion of the rotor 3, so that there is sufficient space between the outer peripheral surface of the hollow rotary shaft 3 and the inner peripheral surface of the stator 7. A large space can be secured. Therefore, it is possible to improve the characteristics of the motor unit 1 by using the rotor 3 using a large core, a magnet, or the like.

On the other hand, according to this embodiment, the rotor 5
The diameter of the large diameter portion 3b can be set as large as possible irrespective of the size of the screw nut 15, that is, the accommodation space for the screw nut 15 can be enlarged as much as possible. For this reason, the selection range of the screw type and the size of the screw nut 15 is widened, and it is possible to use a large screw nut 15 having a high load-bearing strength. When a large screw nut 15 is used, as shown in the figure,
It is desirable that the bearings 9 are arranged in a plurality of stages (two stages in this example) around the outer periphery of the screw nut 15 to more strongly suppress the vibration of the hollow rotary shaft 3 and the screw nut 15.

In the linear actuator according to the above embodiment, the end face of the lock nut 11 on the side opposite to the thrust radial bearing 9 is larger than the open end of the rotary shaft 3 on the large diameter portion 3b side. It is located near the side. The portion of the screw nut 15 except for the flange portion 15a is housed in the large diameter portion 3b of the rotating shaft 3. Therefore, screw nut 15
When the flange portion 15a is fastened to the lock nut 11 with the bolt 17, the flange portion 15a and the lock nut 1
An annular gap 19 is formed between the flange portions 1 and
5a comes into contact with the opening end of the rotary shaft 3 on the large diameter portion 3b side.

The tightening force of the bolt 17 is in the direction of compressing the gap, that is, the flange portion 15a and the lock nut 1
1 act in a direction to attract each other, the flange portion 15a is extremely strongly pressed against the opening end of the large diameter portion 3b, and a thrust force acts on the lock nut. As a result, the inertia force of the screw nut 15 Is prevented from being loosened. In addition, since a compression reaction force acts on the bolt 17, the loosening of the bolt 17 is also prevented.

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 slide screw shaft is used as the output screw shaft 13, the screw nut 15 is used. As a sliding screw nut is used.

In the above embodiment, the small diameter portion 3 of the rotating shaft 3
a is provided with a step 3c, and the rotor 5 is positioned by bringing the end face of the rotor 5 into contact with the step 3c, but the boundary between the small diameter section 3a and the large diameter section 3b is The end face of the rotor 5 may be set at the position of the step 3c so that the end face of the rotor 5 contacts the step at this boundary. Further, the peripheral surface of the small diameter portion 3a is formed flat, and the small diameter portion 3a is formed.
Can be set arbitrarily.

FIG. 2 shows another embodiment of the linear actuator according to the present invention. In this embodiment, an end of the hollow rotary shaft 3 on the small diameter portion 3a side is extended to provide a solid shaft portion 3c smaller in diameter than the small diameter portion 3a, and a sensor (output screw shaft) is provided on the shaft portion 3c. (A rotary sensor such as an encoder and a resolver for detecting the rotational speed and the moving position of the motor) and / or a brake (not shown). According to this configuration, the function of detecting the moving speed and position of the output screw shaft 13 and / or the function of braking the screw shaft 13 can be realized with a compact configuration.

[0022]

According to the present invention, the hollow rotary shaft has a stepped structure having a small-diameter portion and a large-diameter portion, and the rotor of the motor section is mounted on the small-diameter portion and the inside of the large-diameter portion is provided. Since the screw nut is disposed in the above, the following effects can be obtained. (1) The diameter of the small-diameter portion of the hollow rotary shaft can be set as small as possible within a range in which the condition that the linear motion of the output screw shaft is not hindered is satisfied. Therefore, it is possible to improve the characteristics of the motor unit by using a rotor having a large core, a magnet, or the like. (2) The diameter of the large-diameter portion of the hollow rotary shaft can be set as large as possible irrespective of the size of the rotor, that is, the accommodation space for the screw nut can be expanded as much as possible. For this reason, the selection range of the screw type and the size of the screw nut is widened, and a large screw nut having high load bearing strength can be used.

[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 another embodiment of the linear actuator according to the present invention.

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 (5)

[Claims] 1. A motor having a hollow rotary shaft, an output screw shaft coaxially penetrating the hollow rotary shaft, and screwed with the output screw shaft disposed in the hollow rotary shaft. A screw nut that converts the rotational motion of the hollow rotary shaft into a linear motion of the output screw shaft via the screw nut, wherein the hollow rotary shaft has a small diameter portion and a large diameter. A linear actuator having a stepped structure having a diameter portion, wherein the rotor of the motor portion is mounted on the small diameter portion, and the screw nut is disposed in the large diameter portion. 2. The linear actuator according to claim 1, wherein the hollow rotary shaft is supported by a plurality of thrust radial bearings at a position where the screw nut is provided. 3. The motor according to claim 1, wherein the rotor of the motor portion is positioned by a step portion present at a boundary between the small diameter portion and the large diameter portion of the hollow rotary shaft. Linear actuator. 4. The linear actuator according to claim 1, wherein an end of the small-diameter portion of the hollow rotary shaft is extended, and a component of a rotation sensor is added to the extended portion. 5. The linear actuator according to claim 1, wherein an end of the small-diameter portion of the hollow rotary shaft is extended, and a brake component is added to the extended portion.