JP2009008162A - Linear actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a linear actuator capable of reducing cost and weight without losing a function of a jack screw mechanism. <P>SOLUTION: The jack screw mechanism 3 is equipped with a jack screw 31, a nut body 32 screwed to the jack screw 31 and capable of advancing and retreating by following the rotation of the jack screw 31, and a guide housing 33 capable of storing the jack screw 31 and the nut body 32 in an internal space. The nut body 32 is provided with a first bearing 321A and a second bearing 321B capable of rolling with a first shaft 321a and a second shaft 321b that are substantially orthogonal to the axial direction of the jack screw 31 as a center. The guide housing 33 has a first guide groove 33A and a second guide groove 33B spliced to outer peripheral faces of the first bearing 321A and the second bearing 321B, respectively. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a linear actuator.

  2. Description of the Related Art Conventionally, linear actuators that can handle high loads are known that include an electric motor and a motion conversion mechanism (for example, a jack screw mechanism) that converts the rotational motion of the electric motor into linear motion.

  As an example, spline processing is performed on the outer peripheral surface of the nut body that can be engaged with the jack screw and the inner peripheral surface of the guide housing that can be brought into contact with the outer peripheral surface of the nut body, and using this spline fitting, A mode in which the nut body is moved forward and backward along the axial direction of the jack screw by following the rotation of the jack screw. Note that such conventional techniques are appropriately implemented in the field, and none are disclosed as patent documents.

  However, the conventional one has to process splines on the outer peripheral surface of the nut body and the inner peripheral surface of the guide housing, respectively, and there is a problem that high processing accuracy is required in addition to increasing processing costs. Further, the guide housing must be formed from a steel material such as stainless steel so that it can withstand a high load, which causes a problem that the weight of the entire linear actuator is increased.

  The present invention has been made paying attention to such problems, and a main purpose thereof is to provide a linear actuator that can be reduced in cost and weight without impairing the function of the motion conversion mechanism. It is in.

  That is, the linear actuator of the present invention includes a motor and a motion conversion mechanism that converts the rotational motion of the motor into a linear motion, and the motion conversion mechanism includes a screw shaft and the screw shaft. And a guide housing capable of accommodating the screw shaft and the nut body in an internal space, and the nut body, A rolling element capable of rolling about an axis substantially orthogonal to the axial direction of the screw shaft is provided, and a guide groove that is in contact with the outer peripheral surface of the rolling element and guides the forward and backward movement of the nut body is provided in the guide housing. It is provided.

  In such a case, the nut body is moved forward and backward while rolling with the rolling element in contact with the guide groove provided in the guide housing. It is not necessary to perform spline processing on the outer peripheral surface and the inner peripheral surface of the guide housing, respectively, and it is possible to effectively reduce the processing cost and to form the guide groove in the guide housing, so the spline is processed in the guide housing. Compared with the embodiment, it is excellent in terms of workability. In addition, excessive contact pressure acts on the nut body and guide groove when operated at high load, but by rolling the rolling element in contact with the guide groove, the nut body is in direct contact with the guide groove. Compared with a mode in which the advancing and retreating operation is performed in a state of being moved, the load acting on the nut body and the guide groove can be effectively reduced. As a result, the guide housing is formed from a material other than steel, for example, aluminum. It is possible to reduce the weight of the entire actuator.

  As a particularly preferred embodiment, an embodiment in which a bearing is applied as a rolling element can be mentioned. Thereby, it is possible to make the linear motion of the nut body smoother.

  As described above, according to the present invention, it is possible to provide a linear actuator that can be reduced in cost and weight without impairing the function of the motion conversion mechanism.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

  As shown in FIG. 1, the linear actuator 1 according to the present embodiment includes a motor 2 and a motion conversion mechanism (jack screw mechanism 3) that converts the rotational motion of the motor 2 into linear motion. In the present embodiment, an electric motor is applied as the motor 2. That is, the linear actuator 1 according to the present embodiment is an electric linear actuator. Moreover, in this embodiment, the jack screw mechanism 3 provided with the jack screw 31 which is the screw shaft of this invention is applied as a motion conversion mechanism.

  The electric motor 2 includes a motor main body 21 and a rotating shaft that protrudes from one end surface of the motor main body 21 and rotates about an axis. Then, the rotation of the rotating shaft is decelerated by a reduction mechanism composed of one or a plurality of gears (not shown) and output to the jack screw mechanism 3.

  The jack screw mechanism 3 is connected to the terminal end of the speed reduction mechanism and functions as an output shaft, and a nut body 32 that can be moved forward and backward by the rotation of the jack screw 31 while being screwed into the jack screw 31. And a guide housing 33 capable of accommodating the jack screw 31 and the nut body 32 in the internal space.

  The jack screw 31 has a male screw cut on the outer peripheral surface, and is rotatably supported by the jack screw bearing 31a. A portion connected to the terminal end of the speed reduction mechanism corresponds to the input end of the jack screw mechanism 31.

  The nut body 32 is provided on the inner peripheral surface of a nut main body 321 having a female screw threadably engageable with the male screw of the jack screw 31 and the nut main body 321 integrally or integrally therewith, and the jack screw 31 is provided in a cylindrical internal space. A tube-shaped portion 322 that can be accommodated is provided. In FIG. 1, a nut body 32 integrally including a nut main body 321 and a tube-shaped portion 322 is illustrated.

  Thus, the nut body 321 is provided with a bearing (first bearing 321A, second bearing) that can roll about an axis substantially orthogonal to the axial direction of the jack screw 31 (in other words, the advancing and retreating direction of the nut body 32). 321B). In the present embodiment, the nut main body 321 is provided with a first shaft 321a extending upward (motor 2 side) and a second shaft 321b extending downward (counter motor 2 side). A single bearing (first bearing 321A and second bearing 321B) is rotatably supported on each of the first shaft 321a and the second shaft 321b). That is, in this embodiment, the nut main body 321 is provided with a pair of upper and lower bearings (first bearing 321A and second bearing 321B).

  The guide housing 33 is made of, for example, an aluminum material, and the first guide groove 33A and the second guide groove 33B that can be brought into contact with the outer peripheral surfaces of the first bearing 321A and the second bearing 321B provided on the nut body 32 are arranged in the longitudinal direction (in other words, In this case, the nut body 32 is formed along the advancing / retreating direction). A linear guide mechanism that guides the linear motion of the nut body 32 is configured by the bearings (first bearing 321A, second bearing 321B) and guide grooves (first guide groove 33A, second guide groove 33B).

  The first guide groove 33A has opposing walls 33a that face each other, the second guide groove 33B has opposing walls 33b that face each other, and the spacing between the opposing walls 33a and the opposing walls 33b that form a pair of the first guide grooves 33A. Is set to be approximately the same as or slightly larger than the diameter of the bearings (first bearing 321A, second bearing 321B). In the present embodiment, the upper side of the first guide groove 33A is closed by the upper wall 331, while the second guide groove 33B is opened downward, and the lower opening can be closed by the cover 4. (See FIG. 1).

  Next, the operation of the linear actuator 1 according to this embodiment will be described.

  The output from the electric motor 2 is transmitted to the jack screw mechanism 3 after being decelerated by the speed reducer, and the nut body 32 is connected to the first bearing 321A and the reverse motion of the rotating shaft of the electric motor 2 in accordance with the forward rotation motion or the reverse rotation motion. The second bearing 321B is linearly moved along the axial direction of the jack screw 31 while being guided by the first guide groove 33A and the second guide groove 33B formed in the guide housing 33, respectively. More specifically, the first bearing 321A and the second bearing 321B slide while rolling while the outer peripheral surfaces of the first bearing 321A and the second bearing 321B are in contact with the first guide groove 33A and the second guide groove 33B, respectively. The torque reaction of the jack screw 31 is received, and the linear motion of the nut body 32 is smoothly and appropriately guided.

  As described above, in the linear actuator 1 according to the present embodiment, the nut body 32 is provided with axes (first shaft 321a and second shaft 321b) that are substantially orthogonal to the axial direction of the jack screw 31, that is, the advancing / retreating direction of the nut body 32. Roller-bearing bearings (first bearing 321A and second bearing 321B) are provided at the center, and the guide housing 33 is in contact with the outer peripheral surface of the bearing (first bearing 321A and second bearing 321B) and the nut body 32 Guide grooves (first guide groove 33A, second guide groove 33B) for guiding the advance / retreat operation are provided, bearings (first bearing 321A, second bearing 321B) and guide grooves (first guide groove 33A, second guide groove 33B). ) To form a linear guide mechanism that guides the linear motion of the nut body 32. Thus, it is not necessary to perform spline processing on the outer peripheral surface of the nut body and the inner peripheral surface of the guide housing, respectively, and the processing cost can be reduced, and the load generated during the rotation operation of the jack screw 31 is reduced by the guide groove (first guide). The outer peripheral surface of the bearing (first bearing 321A, second bearing 321B) that rolls along the groove 33A, the second guide groove 33B) and the opposing wall of the guide groove (first guide groove 33A, second guide groove 33B) Since they are received by contact between the surfaces of the (facing wall 33a and facing wall 33b), it is possible to effectively reduce the load applied to the guide grooves (first guide groove 33A, second guide groove 33B) itself. As a result, the guide housing 33 can be formed from a material other than steel, such as aluminum. It is possible to achieve even lighter.

  In particular, in this embodiment, the bearings (first bearing 321A, second bearing 321B) are applied as rolling elements that roll along the guide grooves (first guide groove 33A, second guide groove 33B). The linear motion of the nut body 32 along the guide grooves (the first guide groove 33A and the second guide groove 33B) can be made smoother.

  The present invention is not limited to the embodiment described in detail above.

  For example, in the above-described embodiment, the embodiment in which the jack screw mechanism is applied as the motion converting mechanism that converts the rotational motion of the motor into the linear motion has been exemplified. However, a ball screw mechanism may be applied instead of the jack screw mechanism. . Further, a motor other than electric, for example, a motor using air pressure or hydraulic pressure as a driving source may be applied as the motor.

  Further, as the rolling element, a door wheel may be used instead of the bearing.

  Moreover, the aspect which rolls a some rolling element in one guide groove, or the aspect which provided the guide groove 1 or 3 or more in the guide housing may be sufficient. In this case, at least one rolling element may be rolled in each guide groove.

  Further, as described above, the guide housing is preferably made of a material other than steel from the viewpoint of weight reduction, and as the material, a material other than aluminum may be applied.

  In addition, the specific configuration of each part is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

1 is an overall schematic view schematically showing a linear actuator according to an embodiment of the present invention with a part broken away. FIG. 2 is a diagram schematically showing a state where a cover is not attached, as viewed in the x direction of FIG. 1.

Explanation of symbols

1 ... Linear actuator 2 ... Motor (electric motor)
3. Motion conversion mechanism (jack screw mechanism)
31 ... Screw shaft (jack screw)
32... Nut bodies 321a, 321b... Axis (first axis, second axis)
321A, 321B ... rolling elements (first bearing, second bearing)
33 ... guide housings 33A, 33B ... guide grooves (first guide groove, second guide groove)
4 ... Cover

Claims (2)

A linear actuator comprising a motor and a motion conversion mechanism that converts the rotational motion of the motor into a linear motion,
The motion conversion mechanism includes a screw shaft, a nut body that is screwed to the screw shaft and is capable of moving forward and backward as the screw shaft rotates, and a guide housing that can accommodate the screw shaft and the nut body in an internal space. With
The nut body is provided with a rolling element capable of rolling about an axis substantially orthogonal to the axial direction of the screw shaft, and the guide housing is brought into contact with the outer peripheral surface of the rolling element and the nut body is advanced and retracted. A linear actuator, characterized in that a guide groove for guiding is provided. The linear actuator according to claim 1, wherein the rolling element is a bearing.

Images