JP7439646B2 - linear motion device - Google Patents

Description

The present invention relates to a linear motion device.

For example, Patent Document 1 listed below describes a linear motion device that converts one of linear motion and rotational motion into the other motion. In this example, a shaft having a male thread and a nut having a female thread are screwed together. A rail is provided on the outside of the nut and extends parallel to the direction in which the shaft extends. A slide member that is slidable in the extending direction of the rail is attached to the rail, and this slide member and a nut are connected. The shaft is immovable in the extending direction of its central axis, and is rotatably supported around its central axis. That is, the shaft is rotationally driven by an electric motor, so that the nut moves along the rail. In other words, the rotational motion of the shaft is converted into linear motion of the nut.

Patent No. 6106835

(Problem to be solved by the invention)
Here, when the nut and shaft of the linear motion device are stationary, an external force (an external force that moves the nut linearly or an external force that rotates the shaft) may act on the nut or the shaft. At that time, the nut and shaft may not be able to remain stationary.

The present invention was made in order to deal with the above problem, and its purpose is to provide a linear motion device equipped with a shaft and a nut, which can be used when an external force is applied to the nut or shaft while the nut and shaft are stationary. The object of the present invention is to provide a linear motion device capable of keeping the nut and shaft stationary even when the nut and shaft are in a stationary state.

(Means for solving problems)
In order to achieve the above object, a linear motion device according to the present invention includes a shaft and a nut that each have a threaded portion, are screwed together at the threaded portion, and a support that supports the nut or the shaft. and a member.
A first uneven portion extending parallel to the central axis of the shaft or the nut is provided on the outer circumferential surface of a portion of the shaft excluding the male threaded portion or on the outer circumferential surface of the nut, and A second uneven portion to be fitted is provided on the support member, a magnetorheological fluid is sealed in a fitting portion between the first uneven portion and the second uneven portion, and a magnetic field is generated to generate a magnetic field in the fitted portion. A generator is provided.
In the present invention, the threaded portions of the shaft and the nut may be directly screwed together, or the shaft and the nut may be screwed together via a separate part (for example, a steel ball).

In one aspect of the present invention, the direction of the magnetic field is perpendicular to opposing surfaces of the concave portions and convex portions that constitute the first concavo-convex portion and the second concavo-convex portion.

In another aspect of the present invention, a magnetorheological fluid is sealed in the threaded part of the shaft and the nut, and the magnetic field generating device generates a magnetic field in the fitted part, and A magnetic field is generated in the area.

The magnetic field generator generates a magnetic field in a space filled with magnetorheological fluid, thereby increasing the viscosity of the magnetorheological fluid. As a result, the resistance force (shear stress (shear stress of the magnetorheological fluid cluster)) against the force that moves the second uneven portion and the first uneven portion relatively in the axial direction of the shaft is increased. Therefore, the shaft and the nut are relatively difficult to move in the axial direction of the shaft. That is, the shaft and nut can be kept stationary in the linear motion device.

FIG. 1 is a perspective view showing the front, left side, and top surface of a linear motion device according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the linear motion device of FIG. 1. FIG. FIG. 3 is a perspective view of the shaft. It is a perspective view of a nut. It is a perspective view of a support stand. FIG. 3 is a cross-sectional view (perspective view) showing a fitting portion between the support base and the spline. FIG. 3 is a cross-sectional view (plan view) showing a fitting portion between the support base and the spline. It is a sectional view (plan view) showing a threaded part and a fitting part. FIG. 3 is a front view showing the direction of magnetic lines of force. FIG. 6 is a perspective view of a shaft, a nut, and a support base of a linear motion device according to a modification of the present invention. FIG. 11 is a cross-sectional view (perspective view) showing a threaded portion and a fitting portion of the linear motion device in FIG. 10; FIG. 11 is a cross-sectional view (plan view) showing a screw portion and a fitting portion of the linear motion device of FIG. 10; It is a sectional view showing a fitting part of a linear motion device concerning another modification.

Hereinafter, a linear motion device 1 according to an embodiment of the present invention will be described. The linear motion device 1 includes a frame 10, a shaft 20, a nut 30, a support base 40, a gear 50, a servo motor 60, an electromagnet 70, and a control device 80 (see FIGS. 1 and 2).

The frame 10 has a support plate 11 (a part of the housing). The support plate 11 is a rectangular plate member. In the following description, the extending direction of the long side of the support plate 11 will be referred to as the X direction, and the extending direction of the short side will be referred to as the Y direction. Further, the thickness direction of the support plate 11 is referred to as the Z direction. The frame 10 also includes brackets 12, 12 that support a nut 30, which will be described later, and a bracket 13 that supports a servo motor 60. The structures of the brackets 12, 12 and the bracket 13 will be described later. Note that in FIG. 2, the support plate 11 is omitted.

The shaft 20 extends in the X direction (see FIG. 3). A cross section perpendicular to the extending direction of the shaft 20 has a circular shape. A male screw portion MS extending in the X direction is formed on the outer circumferential surface of the third shaft 20c excluding the first shaft portion 20a located at one end in the extending direction of the shaft 20 and the second shaft portion 20b located at the other end. has been done. The male threaded portion MS is a multi-thread thread. That is, the male threaded portion MS is composed of a plurality of (for example, eight threads) helical threads that are offset in the circumferential direction of the shaft 20.

The first shaft portion 20a and the second shaft portion 20b are not provided with threads as provided in the third shaft portion 20c. Splines SP, SP extending in the X direction are provided on the outer peripheral surfaces of the first shaft portion 20a and the second shaft portion 20b. That is, the spline SP consists of a plurality of (for example, 12) protrusions _PSP extending in the X direction (see FIG. 9). The cross-sectional shape of this convex portion _PSP is trapezoidal. These convex portions _PSP are arranged at equal intervals in the circumferential direction of the shaft 20. That is, a recess _RSP having a _shape opposite to that of the projection PSP is formed between circumferentially adjacent projections _PSP . The convex portion P _SP and the concave portion R _SP correspond to the first concavo-convex portion of the present invention.

The nut 30 is a cylindrical member extending in the X direction (see FIG. 4). A female threaded portion FS that is screwed into the male threaded portion MS of the shaft 20 is provided on the inner peripheral portion of the nut 30 . That is, the female threaded portion FS is composed of a plurality of helical threads that are respectively threadedly engaged with the plurality of threads that constitute the male threaded portion MS. The total length (dimension in the X direction) of the nut 30 is smaller than the total length of the male threaded portion MS. Furthermore, lubricating oil is sealed (applied) inside the nut 30 at the threaded portion between the male threaded portion MS and the female threaded portion FS. Circular recesses Ra and Rb are provided at the center of one end surface and the other end surface of the nut 30 in the X direction. The annular seals S1, S1 are fitted into the recesses Ra, Rb to prevent the lubricating oil from leaking out of the nut 30.

The support stand 40 includes a support stand (first support stand) 41 that supports the first shaft portion 20a of the shaft 20, and a support stand (second support stand) 42 that supports the second shaft portion 20b of the shaft 20. (See Figure 1).

The support stand 41 has a substantially cylindrical main body MP extending in the X direction and leg parts FP extending downward from the lower surface of the main body MP and fixed to the support plate 11 of the frame 10 (see FIG. 5). A through hole TH _MP penetrating in the X direction is formed in the main body MP. The cross-sectional shape of the through hole TH _MP is substantially the same as the cross-sectional shape of the spline SP of the shaft 20. That is, on the inner peripheral surface of the through hole TH _MP , protrusions P _MP and recesses R _MP are alternately formed in the circumferential direction. A spline SP is inserted into this through hole TH _MP (see FIGS. 5 to 7). Note that the convex portion P _MP and the concave portion R _MP correspond to the second concavo-convex portion of the present invention. Strictly speaking, the inner dimension of the through hole TH _MP is set to be slightly larger than the outer dimension of the spline SP. Therefore, when the spline SP and the main body part MP are fitted together, there is a slight gap between them (see FIG. 9). A magnetorheological fluid MRF is sealed in this gap. Similar to the nut 30, circular recesses Ra _MP and Rb _MP are formed on the front and rear end surfaces of the main body MP (see FIG. 6). Annular seals S _MP and S _MP are fitted into these recesses Ra _MP and Rb _MP to prevent the magnetorheological fluid MRF from leaking from the main body MP (see FIGS. 2 and 7).

The structure of the support stand 42 is substantially the same as that of the support stand 41. However, while the magnetorheological fluid MRF is sealed inside the main body part MP of the support stand 41, lubricating oil is sealed inside the main body part MP of the support stand 42.

The gear 50 is a spur gear (see FIGS. 1 and 2). The gear 50 and the nut 30 are coaxially arranged, and the gear 50 is fixed to the other end surface of the nut 30 in the X direction. The outer diameter of the gear 50 is larger than the outer diameter of the nut 30. Furthermore, the inner diameter of the gear 50 is set to a size that allows the shaft 20 to be inserted therethrough.

The servo motor 60 includes an electric motor 61 and a speed reduction device 62. Further, the servo motor 60 includes a position detection device, a speed detection device, a torque detection device, etc., which are not shown. Furthermore, the servo motor 60 includes a gear 63 attached to its output shaft (output shaft of the reduction gear device 62). The servo motor 60 is arranged to the left of the nut 30 so that the gear 63 meshes with the gear 50. A servo motor 60 is fixed to the support plate 11 via a bracket 13.

The electromagnet 70 (magnetic field generator) has a core 71 and a coil 72 (see FIG. 1). The core 71 has a base 71a extending in the X direction, and a first leg 71b and a second leg 71c extending in the Y direction (toward the shaft 20) from one end and the other end of the base 71a in the extending direction. A coil 72 is formed by winding an electric wire (magnet wire) around the base 71a. The electromagnet 70 is made of a non-magnetic material and is fixed to the support plate 11 via a bracket (not shown). The tip of the first leg portion 71b is arranged to face the side surface of the support base 41. On the other hand, the tip of the f second leg portion 71c is disposed to face the circumferential surface between the male screw portion MS of the shaft 20 and the spline SP of the first shaft portion 20a.

The control device 80 includes a computer including a processing unit (CPU), a storage device, etc., and a power supply device that supplies power to the servo motor 60 and the electromagnet 70 (see FIG. 1). The control device 80 controls the servo motor 60 and the electromagnet 70 according to an operator (for example, a brake pedal) (not shown), a predetermined computer program, and the like.

Here, the configuration of the brackets 12, 12 will be explained. The brackets 12, 12 are arranged at one end and the other end of the nut 30 in the X direction. The configurations of the bracket 12 on one end side in the X direction and the bracket 12 on the other end side are the same, and their orientations in the X direction are opposite. The bracket 12 has a substantially L-shape. That is, the bracket 12 has a first wall portion 121 and a second wall portion 122. The wall thickness direction of the first wall portion 12 is parallel to the X direction. The second wall portion 122 is arranged on one side of the lower end of the first wall portion 121 . The wall thickness direction of the second wall portion 122 is parallel to the Z direction. A through hole TH 121 penetrating in the X direction is formed in the first wall portion ₁₂₁ . The inner diameter of the through hole TH ₁₂₁ is slightly larger than the outer diameter of the male threaded portion MS of the shaft 20.

The brackets 12, 12 configured as described above are fitted into the shaft 20 from one end and the other end in the X direction, respectively. That is, the first shaft portion 20a and the second shaft portion 20b of the shaft 20 are inserted into the through holes TH ₁₂₁ and TH ₁₂₁ of the brackets 12, 12, respectively, and the second wall portion 122 is fixed to the support plate 11.

The nut 30 and the gear 50 are sandwiched between the front bracket 12 and the rear bracket 12, and movement of the nut 30 in the front-rear direction is restricted. Furthermore, the fitting between the splines SP and the main body parts MP allows the shaft 20 to move in the front-rear direction, and restricts the rotation of the shaft 20 about the central axis C.

With no power being supplied to the coil 72, the electric motor 61 is driven so that the gear 63 rotates clockwise when viewed from the other end of the linear motion device 1 in the X direction. This causes the gear 50 and nut 30 to rotate counterclockwise. Note that, as described above, movement of the nut 30 in the X direction is restricted. Further, the rotation of the shaft 20 is restricted by the spline SP and the support base 40. Therefore, the nut 30 rotates around the central axis C between the brackets 12, 12 without moving in the X direction, and the shaft 20 screwed into the nut 30 rotates around the central axis C. The vehicle moves straight toward one end in the X direction without rotating. Note that in this process, since power is not supplied to the coil 72, no magnetic field is generated in the spline SP of the first shaft portion 20a and the main body portion MP of the support base 41. Therefore, in this state, the viscosity of the magnetorheological fluid MRF is relatively low, and the magnetorheological fluid MRF functions as a lubricant.

Note that the control device 80 sequentially detects (calculates) the thrust of the shaft 20 based on the amount of rotation of the servo motor 60 from the normal state, the output torque, and the like.

For example, when the shaft 20 reaches a predetermined position or when the thrust (braking force) of the shaft 20 continues to be higher than a predetermined value for longer than a predetermined time, the control device 80 controls the power supply (direct current control) to the coil 72. current supply). As a result, a magnetic field is generated in the spline SP of the first shaft portion 20a and the support base 41 (see FIG. 8). That is, as shown in FIG. 9, a magnetic field is formed in the first shaft portion 20a of the shaft 20 that spreads approximately radially from the center thereof.

Here, as described above, the cross sections of the protrusion P _SP and the recess R _SP of the spline SP and the protrusion P _SP and the recess R _SP of the through hole TH _MP are trapezoidal. The protrusion P _SP and the recess R _MP fit together, and the protrusion P _MP and the recess R _SP also fit together. In other words, the top surface of the convex portion _PSP and the bottom surface of the recessed portion _RMP are opposed to each other. Further, the top surface of the convex portion _PMP and the bottom surface of the recessed portion _RSP are opposed to each other. Between these opposing surfaces, the direction of the lines of magnetic force is approximately perpendicular to these surfaces, and the particles of the magnetorheological fluid MRF are aligned along this direction to form a cluster. In this way, the apparent viscosity of the magnetorheological fluid MRF sealed within the through hole TH _MP of the support base 41 is increased.

That is, the resistance force (shear stress (shear stress of the cluster of magnetorheological fluid MRF)) against the force that moves the spline SP in the X direction relative to the support base 41 is increased. Therefore, it becomes difficult for the shaft 20 to move in the X direction. In other words, the braking force of the shaft 20 is increased. In this state, the control device 80 cuts off (or reduces) the power supply to the servo motor 60. Even if the power supply to the servo motor 60 is cut off (or reduced), the apparent viscosity of the magnetorheological fluid MRF is increased and the braking force of the shaft 20 is increased, so the position of the shaft 20 in the X direction is (The state in which the shaft 20 and nut 30 are stationary) can be maintained. According to this, there is no need to continue supplying large electric power to the servo motor 60 to maintain the braking force of the shaft 20 at a predetermined value.

As described above, in the linear motion device 1 according to the present embodiment, the mechanism (the spline SP and the support base 40) that restricts the rotation of the shaft 20 functions as a braking device that suppresses the movement of the shaft 20 in the X direction. We are prepared. Therefore, the linear motion device 1 has fewer parts than the above-mentioned conventional linear motion device, and can easily be miniaturized.

Furthermore, the implementation of the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the purpose of the present invention.

In the embodiment described above, a mechanism for regulating the rotation of the shaft 20 (the spline SP and the support base 40) is provided, and the shaft 20 is moved in the X direction by rotationally driving the nut 30. Instead, as shown in FIGS. 10 to 12, a mechanism (spline SP and support base 40A) for regulating the rotation of the nut 30A is provided, and by rotationally driving the shaft 20A, the nut 30A is moved in the X direction. It is also possible to have a configuration in which it is moved to .

Specifically, a spline SP is formed on the outer circumferential surface of the nut 30A, and a support base 40A that fits into the spline SP is provided. Then, the magnetorheological fluid MRF is sealed in the fitting portion between the nut 30A and the support base 40A (see FIG. 12). Then, a magnetic field is generated in the fitting portion using the electromagnet 70A. This also provides the same effects as the above embodiment. Further, in this case, it is preferable that the screwing portion between the male threaded portion MS and the female threaded portion FS is also filled with magnetorheological fluid MRF. According to this, the lines of magnetic force constituting the magnetic field generated by the electromagnet 70 not only pass through the fitting portion between the nut 30A and the support base 40A, but also pass through the screwing portion between the male screw portion MS and the female screw portion FS. It also passes through. Thereby, a stronger braking force can be obtained compared to the above embodiment.

Further, the configuration of the rotation regulating mechanism is not limited to the above embodiment. For example, as shown in FIG. 13, a key groove KG may be formed in place of the spline SP of the shaft 20A, and the key KY may be attached to the key groove KG. In this case, the shape of the through hole TH _MP may be set to be similar to the cross-sectional shape of the portion of the shaft 20 to which the key KY is attached. That is, the cross-sectional shape of a portion of the shaft 20 (or the nut 30) may be set to have a shape different from a circular shape, and the support base 40 that fits into the portion may be used. Then, a magnetorheological fluid MRF may be sealed in this fitting portion to enable generation of a magnetic field at the relevant portion.

Further, in the above embodiment, one electromagnet 70 is used, but a plurality of electromagnets 70 may be arranged in parallel in the circumferential direction of the main body MP.

1... Linear motion device, 10... Frame, 11... Support plate, 12... Bracket, 13... Bracket, 20, 20A... Shaft, 30, 30A... Nut, 40, 40A... Support stand (stone base member), 50... Gear , 60...servo motor, 70,70A...electromagnet (magnetic field generator), 80...control device, MRF...magneto-rheological fluid, _PMP , _PSP ...protrusion, _RMP , _RSP ...recess, SP...spline

Claims (3)

a shaft and a nut each having a threaded portion and screwed together at the threaded portion;
a support member that supports the nut or the shaft;
A linear motion device equipped with
A first uneven portion extending parallel to the central axis of the shaft or the nut is provided on the outer circumferential surface of a portion of the shaft excluding the threaded portion or on the outer circumferential surface of the nut,
A second uneven portion that fits into the first uneven portion is provided on the support member,
A magnetorheological fluid is sealed in a fitting part between the first uneven part and the second uneven part,
A linear motion device, wherein the fitting portion is provided with a magnetic field generating device that generates a magnetic field. The linear motion device according to claim 1,
A linear motion device in which the direction of the magnetic field is perpendicular to opposing surfaces of the concave portions and convex portions that constitute the first concavo-convex portion and the second concavo-convex portion. The linear motion device according to claim 1 or 2,
A magnetorheological fluid is sealed in a threaded portion between the shaft and the nut,
A linear motion device, wherein the magnetic field generating device generates a magnetic field in the fitting portion and also generates a magnetic field in the threaded portion.

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