JPH0942408A - Linear actuator - Google Patents

Abstract

(57) [Abstract] [Purpose] To obtain a structure that can be configured to be small and lightweight and whose length does not change carelessly. [Structure] The rotating shaft 2 is rotated, and the output shaft 17 is displaced through a ball nut 14 screwed with the ball screw portion 13. An intermediate cylinder 22 is provided around the rotary shaft 2 via a roller clutch 25. A friction plate 23 is provided between the end surface of the spacer 22 and the spacer 24 fixed to the housing 1. The thrust ball bearing 4 bears the thrust load applied to the intermediate cylinder 22. When the rotating shaft 2 tends to rotate due to the thrust load, the roller clutch 25 is locked. When the rotating shaft 2 is rotated from the outside and the output shaft 17 is displaced against the thrust load, the roller clutch 25 does not lock. Therefore, the rotary shaft 2 rotates inside the intermediate cylinder 22, and the intermediate cylinder 22 and the friction plate 23 are rotated.
The existence of does not become a resistance.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The linear actuator according to the present invention is used in a state where it is incorporated in various mechanical devices such as a nursing bed, a lifting table, a lifter, and a vehicle jack.

[0002]

2. Description of the Related Art For example, a nursing care bed or the like incorporates a linear actuator, and a manual handle or an electric motor is used as a drive source to freely adjust the angle of the bed on which the care receiver lies. In such a linear actuator,
The following functions (1) and (2) are required. (1) A function that converts the rotational movement of the manual handle or electric motor into the axial movement of the output shaft. (2) A function to prevent the output shaft from displacing regardless of the load applied in the thrust direction when the manual handle or electric motor is stopped. In order to obtain functions such as (1) and (2), the following
A linear actuator such as that described in US Pat.

Minoru Izawa, “Ball Screw and Its Applied Technology,” published by the Industrial Research Group, pages 134 to 136 of this publication disclose a technology relating to an actuator for converting a rotary motion into a linear motion by a ball screw, and the following. A technique for preventing the reverse rotation of the ball screw by any one of (a) to (d) is described. (a) Give the drive motor a braking effect. (b) Use a non-reversible worm gear as the drive gear. (c) Provide a brake device on the drive gear shaft. (d) Use a one-way clutch or a two-way clutch.

Catalog of linear actuators issued by Thomson-Saginaw Co., Ltd. Japanese Patent Laid-Open No. 63-47557, Japanese Patent Laid-Open No. 50-31553, These publications describe rotary motions linearly by a ball screw or other feed screw. A technique relating to an actuator for converting into motion and a technique for preventing reverse rotation of a feed screw by a spring clutch are described.

Japanese Patent Laid-Open No. 61-38892 discloses a technique relating to an actuator that converts a rotational movement into a linear movement by a ball screw, and an electric clutch and brake that are connected and disconnected based on energization of a solenoid. Describes a technique for restricting the rotation of the drive shaft.

[0006] In this publication, a technique relating to an actuator for converting a rotary motion into a linear motion by a ball screw, and a resistor and a one-way clutch formed in a disk shape are applied to an external load. A technique for mitigating the impact at the time of recovery is described.

In this publication, a technique relating to an actuator for converting a rotary motion into a linear motion by a ball screw, and a preload is applied to the ball screw so that a resistance is applied to the ball screw. A technique for adding and adjusting the speed during reverse rotation is described.

[0008]

The techniques described in the above items 1 to 3 have the following problems to be solved.

In the case of the prior art described in [1] First, when the drive motor has a braking action as in (a), the cost and weight of the drive motor increase. or,
When using a non-reversible worm gear as the drive gear as in (b), reliable reverse rotation cannot be prevented unless the lead angle of the worm gear is reduced. On the other hand, if the lead angle is made small, the meshing efficiency becomes poor, and it becomes necessary to use a large electric motor that rotates at a high speed in order to secure a sufficient operating speed. Further, when the actuator is driven by the manual handle, the manual handle must be rotated many times, which is troublesome to operate. Furthermore, in the case of a structure in which a brake device is provided on the drive gear shaft as in (c), or in the case of a structure using a one-way clutch or a two-way clutch as in (d), it is necessary to independently prevent sufficient reverse rotation. Then,
Large-sized brake devices and clutches must be used, and the entire device becomes large.

In the case of the prior art described in (1), in these cases, when the output shaft is displaced by the manual handle or the electric motor through the feed screw mechanism, the spring clutch causes a slight resistance to lower the efficiency. Not only that, but in order to obtain a reliable reverse rotation prevention effect, a considerably large spring clutch must be used.

In the case of the prior art described in (1), in this case, not only the linear actuator itself becomes expensive due to the use of expensive parts, but also an electric clutch and It is inevitable that the entire device will be expensive, such as the need for a control circuit for controlling the brake.

In the case of the prior art described in [1], in this case, the installation space for the disc-shaped resistor and the one-way clutch becomes large, and the size of the entire apparatus becomes large. Moreover, since the purpose is to reduce the impact at the time of return, it is not possible to obtain a reliable reverse rotation prevention effect.

In the case of the prior art described in [3] In this case, although the speed at the time of reverse rotation can be adjusted,
It is impossible to prevent sufficient reverse rotation. The linear actuator of the present invention has been invented to eliminate any such inconvenience.

[0014]

The linear actuator of the present invention is, like a conventionally known linear actuator, a housing and a rotatably supported inside the housing, such as a manual handle or an electric motor. A rotational shaft driven by the driving means, a ball screw portion provided in a part of the rotational shaft, and a plurality of balls screwed around the ball screw portion, and the axial direction of the rotating shaft. With a ball nut that is freely supported only for displacement over
And an output member connected to the ball nut. When an electric motor is used as the drive means, an appropriate speed reducer is provided between the drive shaft of the electric motor and the rotary shaft, but the speed reducer may be reversible. Also, as the output member, a cylindrical output shaft, a coupling portion provided on a slider, or the like can be considered.

Particularly, in the linear actuator of the present invention, the thrust load applied to the rotary shaft can be supported in the cylindrical space between the outer peripheral surface of the rotary shaft and the inner peripheral surface of the housing. A bearing such as a rolling bearing, a spacer that is rotatably supported inside the housing, a friction plate, and a spacer fixed to the housing are connected in series with each other in the acting direction of the thrust load. The thrust loads are arranged in order from the input side. Along with this, a one-way clutch is provided between the inner peripheral surface of the intermediate cylinder and the outer peripheral surface of the rotary shaft.

The friction plate frictionally engages any surface with the opposite surface, that is, the end surface of the spacer cylinder or one side surface of the spacer. The frictional force acting between the two surfaces faces the thrust load applied to the output shaft and is large enough to prevent the rotation of the rotary shaft. Further, the one-way clutch is configured such that, when the rotating shaft tends to rotate based on the thrust load applied to the output member, the one-way clutch is rotated in the rotating direction between the outer peripheral surface of the rotating shaft and the inner peripheral surface of the intermediate cylinder. It locks based on the displacement. The spacer is not necessarily provided independently of the housing. A part of this housing may be brought into direct contact with the friction plate, and this part may function as a spacer.

[0017]

The linear actuator of the present invention constructed as described above is used in a state where a thrust load is applied to the output member. The linear actuator of the present invention assembled in this way operates as follows,
The output member is axially displaced in accordance with the rotation direction of the rotary shaft that is rotationally driven by the drive means.

First, the operation of displacing the output member against the thrust load will be described. In this case, the rotating shaft is rotated in a predetermined direction by the driving means. At this time, the one-way clutch is not locked, and the rotating shaft is rotatable with respect to the intermediate cylinder. Then, in this state, the rotary shaft rotates independently of the intermediate cylinder, the friction plate, and the spacer. Therefore, the presence of each of these members does not resist the rotation of the rotary shaft. As a result, the rotary shaft smoothly rotates in the predetermined direction. Then, the ball nut screwed into the ball screw portion of the rotary shaft is displaced in the axial direction, and the output member is displaced against the thrust load. At this time, the existence of the reverse rotation preventing mechanism does not resist the displacement of the output member.

Next, in a state where the rotational driving force applied to the rotary shaft from the driving means is eliminated, the thrust load is applied to the ball screw portion from the output member through the ball nut and the plurality of balls. The force tends to rotate the rotating shaft in a direction opposite to the predetermined direction. As a result, the one-way clutch locks, and the intermediate cylinder tends to rotate together with the rotary shaft. In this state, in order to rotate the rotary shaft, it is necessary to slide the side surface of the friction plate and the mating surface. Therefore, it is possible to prevent the rotation shaft from rotating based on the thrust load by limiting the friction coefficient between the side surface of the friction plate and the mating surface to a desired value determined by design.

Further, in the state where the rotating shaft is to be reversed by the driving means, in addition to the torque applied to the rotating shaft based on the thrust load, the torque applied from the driving means is applied in the opposite direction. Join. Therefore, the rotating shaft rotates against the frictional force acting between the side surface of the friction plate and the mating surface. At this time, this frictional force acts as a resistance against the rotation of the rotary shaft, so that abrupt rotation of the rotary shaft is prevented.

[0021]

FIG. 1 shows a first embodiment of the present invention. The linear actuator of the present embodiment is assembled in a portion to which a thrust load in the compression direction is applied when using the linear actuator. The housing 1 is manufactured, for example, by die casting an aluminum alloy. Inside the housing 1, a base end portion (the left end portion in FIG. 1) of the rotary shaft 2 is supported by a radial ball bearing 3 and a thrust ball bearing 4 so as to be rotatable only. Of the pair of ball bearings 3 and 4, the radial ball bearing 3 on the left side of FIG. 1 mainly supports a radial load. On the other hand, the thrust ball bearing 4 on the right side of the figure mainly supports the thrust load in the compression direction. Therefore, the inner peripheral half of one side (right side in FIG. 1) of the bearing ring 5 constituting the thrust ball bearing 4 on the right side in FIG. It abuts via the pad 7. Details of the step 6 and the pad 7 will be described later.

The end surface of the inner ring 28 which constitutes the radial ball bearing 3 is attached to the retaining ring 29 which is engaged with the outer peripheral surface of the base end portion of the rotary shaft 2, and the race ring 5 which constitutes the thrust ball bearing 4.
The outer peripheral side portion of one axial direction of the rotary shaft 2 is abutted against the retaining ring 30 locked to the inner peripheral surface of the front end portion (right end portion of FIG. 1) of the housing 1 so that the axial direction of the rotary shaft 2 (see FIG. (Horizontal direction of)) is aimed at positioning.

An electric motor (not shown) capable of rotating in the normal and reverse directions is fixed to a mounting flange 8 formed on the outer surface of the housing 1. A speed reducer 9 is provided between the drive shaft of the electric motor and the rotary shaft 2 so that the torque of the drive shaft can be increased and transmitted to the rotary shaft 2. In the case of the illustrated embodiment, a worm reducer is used as the reducer 9. Therefore, the worm wheel 10 is externally fitted and fixed to one end of the rotary shaft 2.
In the illustrated embodiment, the rotation shaft 2 and the worm wheel 10 are coupled via a key 11 to prevent the worm wheel 10 from rotating with respect to the rotation shaft 2. Further, a worm 12 is supported in the housing 1 so as to be rotatable only in a twisting direction with respect to the rotating shaft 2.
The worm 12 and the worm wheel 10 are meshed with each other so that the rotation of the drive shaft can be transmitted to the worm 12.

On the other hand, a ball screw portion 13 is formed by forming a spiral groove having an arc-shaped cross section in a portion other than the base end portion of the rotary shaft 2. A ball nut 14 is screwed around the ball screw portion 13 via a plurality of balls 15, 15. Then, the base end of a cylindrical output shaft 17, which is an output member, is screwed and fixed to a coupling cylinder 16 formed at the tip (right end in FIG. 1) of the ball nut 14. The ball nut 14 and the output shaft 17 are covered with a tapered cylindrical cover 18. still,
The output shaft 17 and the ball nut 14 are the same as the output shaft 1
Rotation can be prevented by connecting the tip portion (see FIG. 3) of 7 to a predetermined portion. Therefore, in the assembled state of the linear actuator, the ball nut 14 is freely supported around the rotary shaft 2 only for displacement in the axial direction of the rotary shaft 2. The cover 18 is made of synthetic resin or metal, and the protrusions 19 formed on the inner peripheral surface of the base end of the cover 18 are locked in the recessed grooves 20 formed on the outer peripheral surface of the housing 1. , Is fixedly connected to the housing 1. The outer peripheral surface of the base end portion of the cover 18 is tightened with a band 48 (see FIG. 3) as necessary.

At the base end portion of the ball screw portion 13 at a part of the rotary shaft 2, the step portion 6 having a large diameter on the ball screw portion 13 side is formed. Then, the stepped portion 6 is abutted against the inner peripheral portion of one side (the right side surface in FIG. 1) of the thick, circular ring-shaped contact plate 7. Therefore, the compression thrust load applied to the rotary shaft 2 in the leftward direction in FIG. 1 is transmitted to the bearing ring 5 of the thrust ball bearing 4 via the contact plate 7.

In addition, on the inner peripheral surface of the housing 1 at a portion around one end (the right end in FIG. 1) of the worm wheel 10,
An inward flange-shaped locking portion 21 is formed. And
A thick-walled cylindrical spacer 22, a circular ring-shaped friction plate 23, and a circular ring-shaped spacer 24 are provided between the locking portion 21 and the thrust ball bearing 4 to prevent the thrust load in the compression direction from being increased. They are arranged in series in this order from the thrust ball bearing 4, which is the direction of action, toward the locking portion 21.

The intermediate cylinder 22 has an inner diameter that is sufficiently larger than the outer diameter of the rotary shaft 2 and an outer diameter that is slightly smaller than the inner diameter of the housing 1. Therefore, the tube 2
2 is inside the housing 1 without a large rattling,
And it is fitted rotatably (with a clearance fit). Further, the spacer 24 has an inner diameter larger than the outer diameter of the rotary shaft 2, and the rotary shaft 2 is loosely inserted inside the spacer 24. However, the spacer 24 is fixed to the inside of the housing 1 by an interference fit or the like so as not to rotate with respect to the housing 1. Further, the friction plate 23
Has an outer diameter smaller than the inner diameter of the housing 1 and an inner diameter larger than the outer diameter of the rotary shaft 2, and is rotatable relative to the housing 1 and the rotary shaft 2.

Then, any one of the side surfaces of the friction plate 23 and the side surface of the spacer 24 or the end surface of the spacer cylinder 22 are frictionally engaged with each other so as to slide with a predetermined friction force. ing. On the other hand, the other side surface of the friction plate 23 and the end surface of the spacer cylinder 22 or the side surface of the spacer 24 are not slipped by the predetermined friction force. In the illustrated embodiment, the friction area between the one surface of the spacer 24 and the one surface of the friction plate 23 is made larger than the friction area between the other surface of the friction plate 23 and the end surface of the intermediate cylinder 22. Even if one side surface slides against the end surface of the spacer 22, one side surface of the spacer 24 and the other side surface of the friction plate 23 are prevented from being displaced relative to each other. Therefore, the spacer 24
One surface of the friction plate 23 and the other side surface of the friction plate 23 may be bonded.

Further, a roller clutch 25, which is a kind of one-way clutch, is provided between the inner peripheral surface of the intermediate cylinder 22 and the outer peripheral surface of the rotary shaft 2. That is, an outer ring 26 having an inner peripheral surface as a cam surface is fitted in and fixed to the above-mentioned intermediate cylinder 22.
6 does not rotate with respect to the intermediate cylinder 22. A plurality of rollers 27, 27 are provided between the inner peripheral surface of the outer ring 26 and the outer peripheral surface of the intermediate portion of the rotary shaft 2.
As is well known, each of the rollers 27, 27 is elastically pressed in one direction in the circumferential direction by a spring provided between a roller (not shown) and a non-rotating retainer. Therefore, when the intermediate cylinder 22 rotates in a predetermined direction, each roller 2
7 and 27 do not bite into the cam surface,
Is allowed to rotate. On the other hand, when the intermediate cylinder 22 rotates in the opposite direction, the rollers 27, 27 bite into the cam surface, and the intermediate cylinder 22 does not rotate inside the housing 1.

The linear actuator of the present invention configured as described above is, for example, a base end portion of the housing 1 (see FIG. 1).
The left side end portion of the output shaft 17 has a fixed side mounting portion 31 as a fixed shaft, and the displacement side mounting portion 32 (see FIG. 3, which will be described later, omitted in FIG. 1) formed at a tip portion of the output shaft 17 serves as a displacement shaft. , Support each. Since this displacement shaft tends to be displaced in the direction approaching the fixed shaft, the linear actuator of this embodiment is used in a state in which a thrust load in the compression direction is applied to the output shaft 17. The linear actuator of the present invention thus assembled makes the output shaft 17 axially displaced based on the rotation direction of the drive shaft of the electric motor by acting as follows.

First, the operation of extending the linear actuator by rotating the drive shaft of the electric motor in the forward direction and displacing the output shaft 17 against the thrust load will be described. In this case, the rotary shaft 2 rotates in a predetermined direction via the speed reducer 9, the roller clutch 25 does not lock, and the rotary shaft 2 is rotatable with respect to the intermediate cylinder 22. Therefore, in this state, the rotary shaft 2 rotates with respect to the intermediate cylinder 22, the friction plate 23, and the spacer 24, and the existence of these members 22, 23, and 24 does not provide resistance to the rotation of the rotary shaft 2. I won't. Further, the roller clutch 25 acts like a roller bearing to allow the rotation of the intermediate cylinder 22. Therefore, the existence of the roller clutch 25, which is a one-way clutch, does not resist the rotation of the rotary shaft 2.

As a result, the rotary shaft 2 smoothly rotates in a predetermined direction with the normal rotation of the drive shaft. Then, the ball nut 1 screwed into the ball screw portion 13 of the rotating shaft 2
4 is displaced in the axial direction (rightward in FIG. 1) to displace the output shaft 17 against the thrust load. At this time, as described above, the presence of the intermediate cylinder 22, the friction plate 23, the spacer 24, and the roller clutch 25, which constitute the reverse rotation prevention mechanism, does not resist the displacement of the output shaft 17. Therefore, the driving force of the electric motor is effectively used to displace the output shaft 17. As a result, the linear actuator can be sufficiently extended without using a particularly large electric motor or increasing the reduction ratio (torque increase ratio) of the speed reducer 9. Further, as described below, the speed reducer 9 does not necessarily have a structure that cannot be reversed. Therefore, even when a worm gear reducer is used as in the present embodiment, it is possible to improve the meshing efficiency by increasing the lead angle of the worm gear and to secure a sufficient operating speed with a small electric motor.

Next, in the state where the drive shaft is stopped,
The rotary shaft 2 tends to rotate in a direction opposite to the predetermined direction due to a force applied to the ball screw portion 13 from the output shaft 17 via the ball nut 14 and the plurality of balls 15, 15 based on the thrust load. . As a result, the roller clutch 25 is locked and the intermediate cylinder 22 tends to rotate together with the rotary shaft 2. In order to rotate the rotary shaft 2 in this state, it is necessary to slide the side surface of the friction plate 23 and the end surface of the intermediary cylinder 22, which is the mating surface.
Therefore, by restricting the friction coefficient between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22 to a desired value determined by design, the rotation shaft 2 is prevented from rotating based on the thrust load. it can.

Furthermore, in addition to the torque applied to the rotary shaft 2 based on the thrust load in the state where the drive shaft is reversed, the torque transmitted from the drive shaft through the speed reducer 9 is opposite to the above-mentioned opposite. Join in the direction. Therefore, the rotating shaft 2
Rotates against the frictional force acting between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22. At this time, this frictional force acts as a resistance against the rotation of the rotary shaft 2, so that the rapid rotation of the rotary shaft 2 is prevented.
Therefore, if the friction coefficient between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22 and the drive torque of the electric motor are set to appropriate values, the linear electric actuator can be smoothly expanded and contracted with a small electric motor. Can be done by.

Next, a method of setting the coefficient of friction between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22 will be described. The symbols used in the following description have the following meanings. Further, it is assumed that the degree to which the speed reducer 9 contributes to the reverse rotation prevention is ignored (the speed reducer 9 has no reverse rotation prevention function). F: Thrust load applied to the output shaft 17 in the compression direction μ: Friction coefficient between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22 D: Average of the contact portion between the side surface of the friction plate 23 and the end surface of the intermediate cylinder 22 the diameter L: the ball screw lead T: in order to extend the linear actuator, actuation torque T'be added to the rotary shaft 2 on the basis of the thrust load in the compression direction applied to the rotating shaft 2 torque T _b: the side surface of the friction plate 23 Brake torque based on friction between the rotor and the end face of the intermediate cylinder 22 η: Ball screw transmission efficiency when the rotary shaft 2 rotates forward η ′: Ball screw transmission efficiency when the rotary shaft 2 rotates reversely

T = (F · L) / (2 · π · η) −−− (1) and T ′ = (F · L · η ′) / (2 · π) −−− (2) And T _b = (μ · F · D) / 2 −−− (3). For the total length of the linear actuator even when energization is stopped to the electric motor is not Chijimara the thrust load is required to be a _{T b>T'--- (4)} . In order to use an electric motor with a drive torque as small as possible, the drive torque required for the drive shaft when contracting the entire length of the linear actuator is the drive torque required for the drive shaft when expanding. The following is preferable. The torque to be applied to the rotary shaft 2 when the linear actuator contracts is (T
_b- T '). Therefore, it is preferable that T ≧ (T _b −T ′) −− (5). When the expressions (4) and (5) are summarized, T + T ′ ≧ T _b > T ′ −−− (6). Further, substituting the equations (1) to (3) into the equation (6), (L / π · D) · {η ′ + (1 / η)} ≧ μ> (L · η ′) / (π -D) --- (7). For example, in the case of a linear actuator incorporated in an electric care bed, L≈5 mm, D≈16 m
Those with m, η≈η′≈0.9 are produced. Substituting this condition into the above formula (7), 0.20 ≧ μ> 0.09 --- (8), so that it can be expanded and contracted using a small electric motor. It turns out that a linear actuator that does not contract when energized can be constructed.

The rotary shaft 2 may be rotationally driven not only by an electric motor but also by a manual handle directly or through a speed reducer. Further, even when the rotating shaft 2 is rotationally driven by an electric motor, it is possible to adopt a structure in which, for example, a rotational force is transmitted by a cable wire or the like, and the worm 12 is rotationally driven by the tip portion of this cable wire. . With such a structure, the electric motor can be installed in a portion apart from the linear actuator, so that the degree of freedom of installation in a limited space is increased.

Next, FIG. 2 shows a second embodiment of the present invention. In the case of this embodiment, it is used in a portion to which a thrust load in the pulling direction is applied. Therefore, in the case of the present embodiment, the inward flange-shaped locking portion 33 formed on the inner peripheral surface of the front end portion (right end portion in FIG. 2) of the housing 1 and the front end surface of the intermediary cylinder 22 (right end surface in FIG. 2). ) Between the friction plate 23 and the spacer 24
And are sequentially provided from the side of the intermediate cylinder 22. Also, the rotating shaft 2
Is rotatably supported inside the housing 1 by a pair of deep groove type ball bearings 34a and 34b. Both ball bearings 34a and 34b support not only radial load but also thrust load. In particular, the ball bearing 3 facing the intermediate cylinder 22
4b is a large one so that a sufficiently large thrust load can be supported. A slide bearing 36 is provided on the outer peripheral surface of the intermediate cylinder 22 so that the intermediate cylinder 22 can be smoothly rotated inside the housing 1 without rattling.

When the linear actuator of the present embodiment constructed as described above is used, the thrust load applied to the rotary shaft 2 in the pulling direction is the retaining ring 29 locked to the base end of the rotary shaft 2. Through the inner ring 28 of the ball bearing 34a, the worm wheel 10, and the ball bearing 34b.
Added to 2. In the case of the present embodiment, as the thrust load changes from the compression direction to the pulling direction, the direction in which the roller clutch 25 is locked is changed (when the rotating shaft 2 tends to rotate due to the thrust load in the pulling direction). It locks to. Other than that, the basic configuration and operation are almost the same as those of the first embodiment described above.

Next, FIG. 3 shows a third embodiment of the present invention. In the case of this embodiment, as in the case of the first embodiment described above, it is used in the portion to which the thrust load in the compression direction is applied. In the case of this embodiment, the rotary shaft 2 is configured to be rotationally driven by a manual drive handle 37 via a universal joint 38. For this reason, this embodiment has a structure in which the base half portion (left half portion in FIG. 1) of the housing 1 is omitted from the first embodiment described above, and the universal joint 38 is arranged in this portion.

A deep groove type ball bearing 39 is used as a bearing for supporting the thrust load in the compression direction. Then, the outer end surface of the inner ring 40 that constitutes the ball bearing 39 (see FIG.
The right end surface of the outer ring 41 is abutted against the stepped portion 6 formed on the rotary shaft 2, and the inner end surface of the outer ring 41 (the left end surface of FIG. 3) is abutted against the tip surface of the intermediate cylinder 22. Therefore, the thrust load in the compressing direction applied to the rotary shaft 2 is transmitted from the ball bearing 39 to the intermediate cylinder 22, and the base end surface of the intermediate cylinder 22 and one side surface of the friction plate 23 (the right surface in FIG. 3) are frictionally engaged. To combine. Other configurations and operations are almost the same as those of the first embodiment described above.

Next, FIG. 4 shows a fourth embodiment of the present invention. This embodiment is used in a portion where compression, tension, and thrust loads in both directions may be applied. Therefore, in the case of this embodiment, the spacers 24a and 24b and the spacer 22
Two sets of a and 22b, two roller clutches 25a and 25b, and two friction plates 23a and 23b are provided. The rotation directions for locking both roller clutches 25a and 25b are opposite to each other. That is, when one roller clutch 25a (25b) is locked, the other roller clutch 25b (25a) is rotatable. A pair of contact plates 42a and 42b are fixed to the base end of the rotary shaft 2 in a state of sandwiching the pair of intermediate cylinders 22a and 22b from both sides in the axial direction. Then, each of these contact plates 42a, 42b
Thrust roller bearings 43a and 43b are provided between the front end surface of the intermediate cylinder 22a and the base end surface of the intermediate cylinder 22a, respectively.

In the case of this embodiment constructed as described above, when a thrust load in the compression direction is applied, one side (the right side of FIG. 4) of the spacer 24a, the spacer 22a and the roller clutch 25a.
And the friction plate 23a act in the same manner as in the first embodiment described above. On the other hand, when a thrust load is applied in the pulling direction, the other spacer (left side in FIG. 4), the spacer 22b, the spacer 22b, the roller clutch 25b, and the friction plate 23b.
And operate in the same manner as in the second embodiment described above. In the case of this embodiment, the rotary shaft 2 is driven by an electric motor or a manual handle.
When rotating the
a (25b) locks. However, the roller clutch 2 corresponding to the cylinder 22a (22b) that does not receive the thrust load
Even if 5a (25b) is locked, the intermediate cylinder 22a (22b)
Since the frictional force acting between the end surface of b) and the friction plate 23a (23b) is extremely small, the intermediate cylinder 22a (22b)
b) rotates with a light force inside the housing 1. Therefore, the drive torque required to rotate the rotary shaft 2 hardly increases.

Next, FIG. 5 shows a fifth embodiment of the present invention. Also in the case of the present embodiment, as in the case of the first and third embodiments described above, it is used in the portion to which the thrust load in the compression direction is applied. In the case of this embodiment, a thrust roller bearing 44 is used as a bearing for supporting the thrust load. The roller clutch 25, which is a one-way clutch, also has a function as a radial roller bearing (the same applies to the fourth embodiment described above). Therefore, in this embodiment, the outward flange portion 45 is formed on the outer peripheral surface of the end portion of the intermediate cylinder 22, and one side surface of the outward flange portion 45 (the right side surface in FIG. 5) and the step portion 6 of the rotary shaft 2 are formed. The thrust roller bearing 44 is provided between the thrust bearing ring 46 fixed by butting. Also, the friction plate 23 and the spacer 2
4 is sandwiched between the other side surface (left side surface in FIG. 5) of the outward flange portion 45 and a step portion 47 formed on the inner peripheral surface of the housing 1.

In the case of this embodiment, the thrust roller bearing 4 which is a bearing capable of supporting the thrust load applied to the rotary shaft 2
4, the outward flange portion 45, which is a part of the intermediate cylinder 22, the friction plate 23, and the spacer 24 are arranged in series with respect to the thrust load in the compression direction applied to the rotary shaft 2. In addition, the outer ring 26 that constitutes the roller clutch 25
Both ends of the extension are extended in the axial direction, and the inner peripheral surface of the extension is a cylindrical outer ring raceway. Then, rollers 49, 49 are provided between the outer ring raceway and the outer peripheral surface of the rotary shaft 2 to form a radial roller bearing. Other configurations and operations are almost the same as those of the first and third embodiments.

[0046]

Since the present invention is constructed and operates as described above, it is possible to inexpensively provide a linear actuator that is small in size and lightweight and can be driven with a small force.

[Brief description of drawings]

FIG. 1 is a sectional view of a main part showing a first embodiment of the present invention.

FIG. 2 is a sectional view of a main part showing a second embodiment of the present invention.

FIG. 3 is a sectional view showing the third embodiment.

FIG. 4 is a cross-sectional view of a main part showing the fourth embodiment.

FIG. 5 is a cross-sectional view of a main part showing the fifth embodiment.

[Explanation of symbols]

 1 Housing 2 Rotating Shaft 3 Radial Ball Bearing 4 Thrust Ball Bearing 5 Bearing Ring 6 Step 7 Contact Plate 8 Mounting Flange 9 Speed Reducer 10 Worm Wheel 11 Key 12 Worm 13 Ball Screw 14 Ball Nut 15 Ball 16 Coupling Tube 17 Output Shaft 18 Cover 19 Protrusion 20 Groove 21 Locking part 22, 22a, 22b Space cylinder 23, 23a, 23b Friction plate 24, 24a, 24b Spacer 25, 25a, 25b Roller clutch 26 Outer ring 27 Roller 28 Inner ring 29, 30 Retaining ring 31 Fixed side mounting part 32 Displacement side mounting part 33 Locking part 34a, 34b Ball bearing 36 Sliding bearing 37 Drive handle 38 Universal joint 39 Ball bearing 40 Inner ring 41 Outer ring 42a, 42b Abutment plate 43a, 43b, 44 Thrust roller bearing 45 Outward flange 46 Thrust track Wheel 47 Step 48 Band 49 Roller

Claims (1)

[Claims] 1. A housing, a rotary shaft rotatably supported inside the housing, a ball screw portion provided on a part of the rotary shaft, and a plurality of balls around the ball screw portion. A linear actuator equipped with a ball nut that is screwed in via a shaft and is supported only for displacement in the axial direction of the rotary shaft, and an output member connected to the ball nut. A bearing capable of supporting a thrust load applied to the rotary shaft in a cylindrical space between the surface and the inner peripheral surface of the housing, an intermediary cylinder rotatably supported inside the housing, and a friction plate. Are arranged in series with each other in the acting direction of the thrust load, and a one-way clutch is provided between the inner peripheral surface of the intermediate cylinder and the outer peripheral surface of the rotary shaft. .