JP3406142B2 - Electric actuator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is, for example, for raising or lowering a seat of a chair, or an electrically driven chair equipped with a mechanism for inclining a back plate of the chair by a certain angle, or a floor of a bed at an arbitrary height. The present invention relates to an improvement in an electric actuator including a drive mechanism for linearly moving structures at two points so as to always face each other or to move away from each other, such as a lifting mechanism for lifting and lowering.

[0002]

2. Description of the Related Art Conventionally, as a device for linearly reciprocating a drive rod, a hydraulic cylinder or an air cylinder has been generally used. The former hydraulic cylinder requires a large-scale hydraulic unit when it is used, and the latter air cylinder requires not only air piping but also a large exhaust noise, which may be a source of noise. In order to use two cylinders as a drive source for raising or lowering or tilting a bed used in a medical institution or a chair for dental treatment, etc., considering the installation space, pressure oil leakage, noise, etc. It was difficult to use.

[0003]

For this reason, in recent years, an electric actuator has been used which converts the rotational movement of an electric motor into a linear reciprocating movement to linearly reciprocate a drive rod connected to an operation object. . Since the drive source of this electric actuator is an electric motor, it can be miniaturized and can be used in a narrow space, which is convenient. And
As a means for actuating the drive rod, for example, a ball nut of the ball screw shaft is fixed to the drive rod in a non-rotatable manner,
By drivingly connecting the drive rod to the ball screw shaft and rotating the ball screw shaft to the right or left by an electric motor, the rotational motion of the ball screw shaft is converted into a linear motion, so that the drive rod (at this time, the operation is performed). (Non-rotatably coupled to the object) is configured for linear reciprocating motion.

However, in the structure of the ball screw shaft, the structure of the ball screw shaft itself is complicated, and high pressure acts due to point contact between the ball screw shaft and the ball, so that good lubrication is always maintained. In particular, it is easy to cause wear and galling of the ball screw part due to poor lubrication, especially in mechanical devices that are difficult to maintain and manage.
There was a problem that impaired reliability.

For this reason, instead of the ball screw shaft, for example, a drive rod is connected via a nut to a screw shaft (not shown) that is decelerated by an electric motor through a speed reducer or the like, and the drive rod is rotated by the rotation of the screw shaft. Electric actuators that move back and forth linearly have been used. As shown in FIG. 15, the nut is provided with a screw portion 101 to which a trapezoidal screw of the screw shaft is screwed on the inner peripheral surface, and on the outer peripheral surface, a flange 1 for setting a mounting position of the drive rod 102.
03, and a groove 104 for locking the drive rod 102, which is circumferentially provided at a predetermined distance from the brim 103, is provided to form a nut 105, and the nut 105 is formed.
14, the nut 105 is first fitted into the drive rod 102, and then the nut 10 is attached.
5, a key 106 protruding from the outer periphery of the collar 5 at right angles to the brim 103.
The key groove 107 provided on the open end side of the drive rod 102.
Engage with.

Continuing, as shown in FIG. 16, the nut 1
A threaded shaft 108 having the same structure as the threaded shaft is screwed into the threaded portion 101 of No. 05, and in this state, the groove 10 on the outer periphery of the nut 105 is
4 is pressed into the groove 104 at the peripheral edge of the drive rod 102 by rolling means such as a roll press, so that the ridge 109 of the drive rod 102 is inserted into the groove 10.
4 is pressed to form a fixing portion X that fixes the nut 105 and the driving rod 102, and thus the driving rod 10
2 and a screw shaft (not shown) are drive-connected by the nut 105 to form an electric actuator.

When the electric actuator is replaced with a ball screw shaft and a drive rod is fixedly attached to a trapezoidal screw of the screw shaft via a nut, good lubrication is always maintained like the ball screw shaft. While the drive rod can be moved linearly without causing the problem that it must be, when the nut is made of a metal material, it cuts the screw part that engages with the screw shaft and the groove on the outer periphery. Since it was manufactured by processing, there was a problem that it took time to manufacture and the manufacturing cost was increased.

For this reason, recently, instead of producing the nut from a metal material, for example, the nut is produced by molding a thermoplastic synthetic resin such as a polyacetal resin. In this case, since the nut may be molded using a synthetic resin, the nut can be manufactured easily and economically, but on the other hand, since the material used is a synthetic resin, the rigidity is very poor. As a result, in FIG. 15, when the nut 105 itself is made of the synthetic resin, a large load is applied to the drive rod 102 by the operation target attached to the tip of the drive rod 102 when the electric actuator is driven. And a fixing portion X fixed to the drive rod 102 of a nut 105 that is fixed to the base end portion of the drive rod 102 and is screwed with a trapezoidal screw of a screw shaft (not shown).
Only then, an excessive load will be concentrated and applied.

When an excessive load is concentrated and applied to the fixing portion X of the nut 105, the nut 105 made of synthetic resin is used.
Has a problem in terms of rigidity as compared with a metal material. Therefore, only the portion in the vicinity of the fixed portion X of the screw portion 101 of the nut 105 is deformed and damaged due to concentration of stress due to the load, or the screw shaft (not shown) In the case where the trapezoidal screw was crimped, a hugging phenomenon occurred, which structurally deformed, and sometimes the function as the screw could not be fulfilled at all. As a result, the screw shaft does not rotate even when the electric motor is driven, and the drive rod 102
There is a problem in that it is difficult to move the vehicle linearly, or conversely, the nut 105 is damaged and the drive rod 102 is unthreaded from the nut 105 and suddenly drives to cause a serious accident.

In particular, the above-mentioned clinging phenomenon of the nut 105 with respect to the screw shaft is likely to occur during continuous operation of the electric actuator. This is because when the fixed portion X of the nut 105 receives stress concentration, the frictional force at that portion increases and overheats, and due to this overheating, the threaded portion 101 of the nut 105.
It is considered that the material undergoes thermal deformation and causes a clinging phenomenon (sticking phenomenon). As a result, if the above-mentioned hugging phenomenon occurs during the operation of the electric actuator, the electric motor cannot withstand an excessive load unless the torque is increased, and the drive suddenly stops to cause a burnout accident. In addition, since the operation of the operation target connected to the electric actuator is stopped, there is a problem that the user of the operation target is greatly annoyed.

In view of the above problems, the present invention disperses / avoids concentration of excessive stress on the nut for drivingly connecting the screw shaft and the drive rod, thereby smoothly and favorably rotating the screw shaft. Accordingly, it is an object of the present invention to provide an electric actuator that enables a smooth linear movement of a drive rod.

[0012]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides an electric motor as a driving means and a speed reducing means for decelerating the rotational output of the electric motor by, for example, converting it from a vertical direction to a horizontal direction. A motion converting means for converting the rotary motion into a linear motion, a driving force control means (braking means) built in the motion converting means for controlling a driving force of the motion converting means, and the motion converting means (screw). It comprises an output means (drive rod) drivably connected to the shaft, and a driving force connection means for drivingly connecting the motion conversion means and the output means.

The driving force connecting means for connecting the motion converting means and the drive rod is a nut made of synthetic resin,
A first screw part screwed inside and outside the nut and screwed with a screw shaft of the motion converting means, and a second screw screwed with a screw part screwed inside the opening end of the drive rod. Portion, a locking portion formed by recessing a part of the screw portion at a predetermined interval in the second screw portion on the outer circumference of the nut, and the second screw of the nut on the drive rod side. It is configured by forming a tongue-shaped locking piece at a position corresponding to the flat locking portion of the nut at the opening end in front of the threaded portion that is screwed with the portion.

[0014]

When the motion converting means and the drive rod are connected by the drive force connecting means, that is, when the nut is attached to one open end of the drive rod, the nut is first flattened on the open end of the drive rod. Drive the nut by inserting the locking part in the direction away from the open end of the drive rod and screwing the second screw part on the outer circumference of the nut and the screw part provided inside the open end of the drive rod. Screw on the rod. Needless to say, when the nut is screwed onto the drive rod, the nut and the drive rod are screwed so that the locking piece formed at the open end of the drive rod matches the flat locking portion on the outer circumference of the nut. Yes. After the nut is screwed in, the locking piece provided on the drive rod side is pressed against the flat locking part side of the nut, and the locking piece is engaged with the locking part to attach the nut to the drive rod. To finish.

After fixing the nut, the screw shaft of the motion converting means is screwed into the first screw portion of the nut, and the motion converting means and the output means (driving rod) are drive-connected.
In this state, when the electric actuator is activated, the load of the operation target connected to the drive rod is applied to the threaded portion between the nut and the trapezoidal screw of the screw shaft via the drive rod. The load of the operation target applied to the drive rod is substantially applied to the threaded portion between the nut and the drive rod because the load is screwed to the drive rod by the screw portion provided on the entire outer circumference thereof. become.

As a result, the nut receives the load of the operation target by the threaded portion formed on the entire outer circumference thereof, that is, the load of the operation target can be dispersed and received by the entire nut. It is possible to favorably prevent the stress due to the load of the operation target from concentrating at one place even in the screwed portion between the nut and the screw shaft. Therefore, when the screw shaft is started, stress is evenly applied to the screwing portion between the screw shaft and the nut over the entire screwing portion, and as a result, the driving means including the electric motor has less torque fluctuation, The problem that the screw shaft cannot be started due to torque fluctuation at startup can be suppressed, and the electric actuator can be satisfactorily driven for a long period of time, whereby the driving operation of the operation target object can be performed smoothly and satisfactorily. .

Further, by forming the first and second screw portions on the inside and outside of the nut itself, it is possible to easily disperse and alleviate the concentration of stress applied to the connecting portion between the screw shaft and the drive rod. And the connection can be done easily,
Moreover, after the drive rod itself is screwed onto the nut, the tongue-shaped locking piece is engaged with the flat portion formed on a part of the outer circumference of the nut to avoid idling with the nut and to avoid the nut itself. Since the fixing can be easily performed, the manufacturing process of the electric actuator can be simplified, and the economical manufacturing can be performed.

[0018]

Embodiments of the present invention will be described below with reference to FIGS. FIG. 1 is a vertical sectional view of an electric actuator A of the present invention. In FIG. 1, 1 is an electric motor that is a drive source of the electric actuator, and 3 is a lower side of the electric motor 1 (lower side of FIG. 1). The rotation output of, for example, a deceleration unit that decelerates from the vertical direction to the horizontal direction and converts it,
For example, as shown in FIG. 4, a worm 4 connected to a rotor shaft (not shown) protruding from the electric motor 1 and a worm wheel 5 meshing with the worm 4 are provided.
Is decelerated at a predetermined rotation speed. The electric motor 1 and the speed reducing means 3 drivingly connected to the electric motor 1 constitute the driving means 6 for the electric actuator A.

Reference numeral 7 denotes a hollow cylindrical casing accommodating and accommodating a speed reducing means 3 drivingly connected to the electric motor 1 and a motion converting means 9 interlocking with the speed reducing means 3 for speed reduction driving. Then, on one end (the left side in FIG. 1) of the casing 7, the electric motor 1 constituting the main part of the drive means 6 is vertically erected vertically as shown in FIG. It is mounted so that it can be rotated.

Next, the structure of the motion converting means 9 will be described. As shown in FIG. 1, the motion converting means 9 has a trapezoidal screw 10 of the same lead screwed on a portion projecting from a cylindrical opening 8 formed at the other end (right side in FIG. 1) of the casing 7. Then, the screw shaft 1 in which the base end side not having the trapezoidal screw 10 is pivotally attached to the worm wheel 5 of the speed reducer 3
1 and a drive rod 13 as a hollow output means drivingly connected via a driving force connecting means (nut) 12 screwed with the trapezoidal screw 10 of the screw shaft 11.

On the other hand, in a portion located inside the opening 8 of the screw shaft 11 inside the casing 7, the screw shaft 11 located on the bottom side inside the opening 8 of the casing 7 (right side in FIG. 1) is A thrust bearing 15 inserted through a collar 14a fixed by using a locking pin or the like; and a radial bearing 17 inserted in a bearing housing 16 fitted on the screw shaft 11 on the speed reducer 3 side, The screw shaft 11 is rotatably supported by a radial bearing 17 and a bearing portion 14b provided on a cover 14 attached to an opening end of the casing 7 that opens toward the reduction gear 3 side.

Further, as shown in FIG. 1, a drive rod 13 as the output means is provided in the opening 8 of the casing 7.
The base end portion of the fixed barrel 8a into which is inserted so as to be able to move forward and backward is fitted so as not to be pulled out. Then, the drive rod 13 loosely fitted to the fixed barrel 8a, as shown in FIG.
When the screw shaft 11 is rotationally driven in a predetermined direction by drivingly connecting it to the screw shaft 11 via the driving force connecting means 12, the screwing action of the driving force connecting means 12 causes the screw shaft 11 to move back and forth in a linear direction to drive the driving rod 13. A member fixed to the tip can be pushed and pulled back.

Next, the structure of the driving force connecting means 12 will be described with reference to FIGS. This driving force connecting means 12
As shown in FIG. 6, it is constituted by a nut 18 and a fastening portion of the drive rod 13 for screwing and fastening the nut 18, and the nut 18 has its fastening portion as shown in FIGS. A first screw portion 19 that is screwed into the trapezoidal screw 10 of the screw shaft 11 is provided on the inner side, and a second screw portion 21 that is screwed with a screw portion 20 that is screwed inside the opening end of the drive rod 13 is provided on the outer periphery.
Are respectively screwed. In addition, the second of the nut 18
As shown in FIGS. 7 and 8, the threaded portion 21 of the drive rod 1
Collar 22 (left side in FIG. 7) for setting the mounting position of No. 3
The flat locking portions 23 are provided in two recesses at a distance of 180 °, for example, in the vicinity thereof. Further, as shown in FIG. 6, a nut 18 is provided at the open end of the drive rod 13.
A tongue-shaped locking piece 24 that is engaged with and held by the locking portion 23 of
It is formed with a space of 180 ° so as to correspond to the locking portion 23 of the nut 18.

The nut 18 is screwed onto the drive rod 13.
In the case of fastening, the rear end side (right side in FIG. 6) of the nut 18 is positioned on the open end side (left side in FIG. 6) of the drive rod 13 as shown in FIG. Screw into. The second screw portion 21 on the outer periphery of the nut 18 is screwed into the screw portion 20 of the drive rod 13, and when the collar edge 22 thereof comes into contact with the open end of the drive rod 13, the screw of the nut 18 is screwed. Stop. After that, the nut 18 is slightly unscrewed and stopped at a position where the locking piece 24 of the drive rod 13 matches the locking portion 23 of the nut 18.

After the nut 18 is screwed, as shown in FIG. 8, the locking piece 24 formed on the drive rod 13 side is pressed by a pressing press or the like in the direction of the arrow in the figure to engage as shown in FIG. The stop piece 24 is non-rotatably engaged and fixed to the flat locking portion 23 recessed in the second screw portion 21 of the nut 18. As a result, the nut 18 can be easily and firmly attached to the drive rod 13 without rotating (idling) by the locking piece 24 that is engaged and held by the locking portion 23.

Next, in FIG. 1, 25 is a motion converting means 9
Is a driving force control means (braking means) for mechanically controlling the rotation of the screw shaft 11 between the bearing housing 16 and the thrust bearing 15. The driving force control means 25 is composed of, for example, a one-way clutch 26. There is. 1 and 5 show an example of attachment of the one-way clutch 26 and its configuration, in which a is an outer race, c is a roller, and d is a roller.
Is a rolling groove whose depth increases as it goes in the direction of rotation of the screw shaft 11, and e denotes a spring, which is configured to prevent the screw shaft 11 from rotating in the opposite direction. The one-way clutch 26 is fixedly supported by a holder 27 mounted between the bearing housing 16 and the thrust bearing 15 while being mounted on the screw shaft 11. That is,
The outer race a of the one-way clutch 26 is attached by being press-fitted and fixed to the holder 27 shown in FIG.

As shown in FIG. 1, the thrust bearing 15 is sandwiched between the collar 14a and the thrust bearing 15 at one end of the holder 27 for fixedly supporting the one-way clutch 26. A brake shoe 28 is fixed to the part. Further, a metal brake disk 29 is provided at the end of the bearing housing 16 corresponding to the brake shoe 28.
Are attached, and the brake shoe 28 and the brake disc 29 are always held in sliding contact with each other.

Thus, this one-way clutch 26
When the screw shaft 11 rotates in the positive direction,
When you try to rotate the
Since the holder 27 is configured to rotate integrally with the screw shaft 11, in this example, when mounting the one-way clutch 26 on the screw shaft 11 between the bearing housing 16 and the thrust bearing 15 shown in FIG. When the screw shaft 11 is to be rotated in the advancing direction of the drive rod 13, this is possible, and conversely, when the screw shaft 11 is to be rotated in the opposite direction, the screw shaft 11 is rotated. Install so as to prevent Therefore, when the screw shaft 11 is rotated by the drive means 6 in the direction in which the drive rod 13 is retracted, the holder 27 that fixedly supports the one-way clutch 26 is rotated integrally with the screw shaft 11 so that the holder is fixed. Brake shoe 28 fixed to 27
The screw shaft 11 is rotated while generating a braking force between the brake shaft 29 and the brake disc 29. In this case, the screw shaft 1
In No. 1, a large braking force is applied and the rotation thereof is suppressed.

Further, in FIG. 1, 30 is a casing 7.
It is a fixing member such as a retaining ring made of a C-shaped ring that is fitted inside the opening end that opens in the direction in which the deceleration means 3 is housed and that prevents the bearing housing 16 from coming off. In FIG. 2, 31,
Reference numeral 31 denotes a pivot shaft of an electric actuator A formed integrally with the casing 7 so as to project in a direction orthogonal to the axial direction of the casing 7, and a screw hole for pivotally supporting the electric actuator A at the center thereof. Mounting holes 32, 32 for the like are formed. Reference numeral 33 is a mounting hole provided at the tip of the drive rod 13. Although the screw shaft 11 is rotatably supported in the casing 7 by a radial bearing 17 and a bearing portion 14b provided on the cover 14, the screw shaft 11 is substantially connected to the radial bearing 17, the bearing portion 14b, and a driving force coupling. It goes without saying that it is rotatably supported by the nut 18 of the means 12 while maintaining the horizontal state.

Next, the operation of the electric actuator A will be described. 10 and 11 show application examples in which the electric actuator A can be used. When the electric actuator A is used, the pivot shafts 31, 31 provided on the base end side of the electric actuator A are brought into contact with a support seat 34 provided at a fixed place such as a floor surface,
From this support seat 34 to the pivot 31 provided in the casing 7,
A pivot pin 35 is inserted into the mounting hole 32 of the shaft 31, and the base end of the electric actuator A is rotatably supported by the support seat 34. Further, the tip of the drive rod 13, which serves as an output means of the tip of the electric actuator A, is attached to the connecting metal fitting 36 at the upper end of the pivotal support part f of the operation target (for example, a seat of a medical treatment chair) B at the attachment hole of the tip of the drive rod 13. 33 is utilized to insert a pivot 37 so as to be drivably connected.

When the electric actuator A is set as described above and the operation object B is raised vertically from an inclined state with the pivotal support portion f as a fulcrum, as shown in FIG. Almost all the load of the operation object B is applied to the driving force connecting means 12 connecting the converting means 9 and the output means, and this load is first screwed to the base end of the drive rod 13 shown in FIG. It is transmitted to the threaded portions 21 and 20 of the nut 18 of the force connecting means 12 and the drive rod 13. When the load is transmitted to the screwing parts 21 and 20,
Since the screwed portions 21 and 20 are formed on the entire outer circumference of the nut 18 in the axial direction thereof, the drive rod 13
The load applied to is evenly distributed in the threaded portions 21 and 20 with the nut 18, and can be satisfactorily received without partial stress concentration.

For this reason, the screw shaft 11 which is screwed into the first screw portion 19 of the nut 18 via the trapezoidal screw 10,
Although the load applied to the drive rod 13 is directly transmitted in the screwed portions 10 and 19 with the nut 18, as described above, the screwed portion 21 with the nut 18 and the drive rod 13 is
Since the load is evenly distributed and applied to 20, the stress due to the load is evenly distributed and applied to the entire threaded portions 10 and 19 of the screw shaft 11 and the nut 18. . Therefore, even if the nut 18 itself is made of synthetic resin, which is less rigid than metal,
Since the stress due to the load is evenly applied to the entire area of the screw portion 19 of the first screw portion 19, the first screw portion 19 avoids the concentration of the stress with respect to the trapezoidal screw 10 of the screw shaft 11 and is damaged due to the stress concentration. Also, the screwed state can be favorably maintained with the hugging phenomenon suppressed.

When the electric actuator A is attached to the operation target B as described above, first, when the drive rod 13 is pushed to raise the operation target B vertically from the inclined state in FIG. When the means 6 is driven to start the electric motor 1, the output from the electric motor 1 rotates through the speed reducing means 3 and the screw shaft 11 of the motion converting means 9 in the direction in which the drive rod 13 advances (for example, to the right).

In this case, that is, before the driving means 6 is driven, the load from the operation object B is applied to the driving force connecting means 12 for connecting the motion converting means 9 and the driving rod 13 constituting the output means, Trapezoidal screw 10 of screw shaft 11 and nut 1
8 is tightly coupled to the threaded portion with the first threaded portion 19, but in this tightly coupled state, the threaded portion 20 of the drive rod 13 is threadedly engaged with the entire second threaded portion 21 of the nut 18. , The stress due to the load from the operation target B is uniformly received and the tightly coupled state is maintained.

Therefore, when the screw shaft 11 is rotated by the drive of the drive means 6, the nut 18 and the drive rod 13 are screwed into the drive rod 13 at their threaded portions 21 and 20.
Since the stress of the load applied from the electric motor 1 is evenly distributed, the stress is well avoided from being concentrated at one point of the screwing portions 21 and 20, and the screwing is performed. Although the output from the means 6 reduces the rotation speed of the rotor,
As it is, it is reliably transmitted to the screw shaft 11 of the motion converting means 9 in a low-speed rotation state and rotated, and the nut 18 is moved to the tip end side of the screw shaft 11 to gradually push out the drive rod 13 to operate. B is pushed clockwise about its pivot point f to raise it from the tilted state shown in FIG. 11 to the vertical state as shown in FIG.

The screw shaft 11 which is rotated by the activation of the electric motor 1 is set so as not to receive the braking force of the driving force control means 25 by the function of the one-way clutch 26 when the driving rod 13 advances. The screw shaft 11 can be smoothly rotated without being braked by the driving force control means 25. When the advance of the drive rod 13 is stopped midway (when the drive means 6 is stopped), the drive rod 13 is braked by the load of the operation target B.
8 is strongly pressed by the brake disc 29 to exert a braking force, and the driving force control means 25 is operated. As a result, the drive rod 13 is braked by the drive force control means 25 and stopped without moving backward due to the braking force of the brake shoe 28.

From the stopped state, the driving means 6
When the operation target B is pushed further in the vertical direction by reactivating the drive rod 13 and advancing the drive rod 13, the load of the operation target B is the drive rod 13 → driving force coupling means 12 → screw shaft 11 → collar 14a → thrust bearing 15 → Holder 27 → Bearing housing 16 and received by the fixing member 30, the load of the operation target B makes the drive coupling between the reduction gear 3 and the electric motor 1 unsmooth, and the output from the drive means 6 is generated. There is nothing to prevent the good transmission to the motion converting means 9, and the output of the driving means 6 can be smoothly transmitted.

Next, for example, when the operation target B is retracted from the vertical state shown in FIG. 10 to the electric actuator A side as shown in FIG. 11, the drive means 6 of the electric actuator A is moved in the opposite direction to the above. It may be rotated, but in this case as well as when the drive rod 13 is advanced, the load of the operation target B is applied to the drive rod 13, so that the nut 18 of the drive force coupling means 12 is The screw shaft 11 of the motion converting means 9 is screwed in a tightly coupled state.

For this reason, the drive means 6 is activated to activate the screw shaft 1
When 1 is rotated, the nut 18 and the drive rod 13 apply the stress applied to the drive rod 13 to the screw portion 21,
Since the screwing is performed so as to effectively disperse the concentration at 20, the output of the electric motor 1 from the driving means 6 is output even if the rotation speed of the electric motor 1 is temporarily reduced when the driving means 6 is started. It is transmitted to the screw shaft 11 of the motion converting means 9 in a low-speed rotation state and is rotated, and the drive rod 13 is retracted to the electric actuator A side as shown in FIG.
Is pulled back counterclockwise about its pivot point f and tilted from the vertical state shown in FIG. 10 as shown in FIG.

When the operation object B moves backward while inclining as shown in FIG. 11, the entire load of the operation object B is applied to the drive rod 13 so that the operation object B is rapidly moved back. However, when a large load is applied to the driving rod 13 as described above, the load is applied to the nut 18 of the driving force connecting means 12.
1 is transmitted to the screw shaft 11 via the shaft, and is pushed to the left in FIG.
The one-way clutch 26 attached to the screw shaft 11 rotates the holder 27 integrally with the screw shaft 11 while pressing firmly to the 9 side, and between the brake shoe 28 and the brake disc 29 fixed to the holder 27. Since the braking force is generated in the drive rod 13, the drive rod 13 does not retreat rapidly even when receiving the full load of the operation target B, but can retreat in a state where the braking force is applied.

That is, when the operation target B is moved backward by the electric actuator A and tilted as shown in FIG. 11, the one-way clutch 2 provided in the motion converting means 9 is used.
6 and the braking means composed of the brake shoe 28 and the brake disk 29 formed between the one-way clutch 26 and the bearing housing 16, the drive rod 13 uses the load of the operation target B effectively and smoothly and safely. It can be operated backwards.

In the present invention, an example in which the driving force control means 25 is installed on the speed reducing means 3 side as shown in FIG. 1 has been described, but the present invention is not limited to this and, for example, FIG.
It goes without saying that the electric actuator A may be used by installing the driving force control means 25 including the one-way clutch 26 on the opening 8 side of the casing 7, as shown in FIG. In this case, the mounting of the driving force control means 25 is omitted because it is the same as that described in FIG. 1, but its use is, for example, as shown in FIG. 13, the base end of the electric actuator A is the operation target B. Is pivotally supported on the support seat 34 above the pivot point f, and conversely, the operation object B is installed on the lower side, and the operation object B is directed toward the electric actuator A side with the pivot point f as the center. That is, it is used when moving up and down, for example, the heavy object W on the operation target B.
12 is lowered, the drive rod 13 is advanced in FIG. 12, and the operation target B shown in FIG. 13 is lowered to the solid line position.

That is, when the operation target B is lowered from the position shown by the two-dot chain line in FIG. 13 to the position shown by the solid line, the drive rod 13 is moved down (advanced in FIG. 12). As a result, the one-way clutch 26 operates to rotate the holder 27 integrally with the screw shaft 11, and the screw shaft 11 rotates by being braked by the brake disk 29 fixed to the holder 27. Therefore, since the total load of the operation target B is applied to the screw shaft 11 via the drive rod 13, when the operation target B descends, the brake shoe 28 provided on the holder 27 and the opening 8 side of the casing 7 side. Since the brake disc 29 provided on the bottom plate is constantly in sliding contact with the vehicle and a braking force is applied thereto, the operation target B can be lowered safely and reliably.

On the contrary, when the operation target B is pulled up from the position shown by the solid line in FIG. 13 to the position shown by the chain double-dashed line, the screw shaft 1
1 smoothly rotates without receiving the braking force of the one-way clutch 26 to move (raise) the operation target B in the direction indicated by the chain double-dashed line in FIG. And on the way, the screw shaft 11
When the rotation is stopped, the brake shoe 28 provided on the one-way clutch 26 side and the brake disk 29 attached to the bottom plate side of the casing 7 located on the drive rod 13 side receive the full load of the operation target B. Since the braking force is applied due to the constant sliding contact, the operation target object B moves backward (falls) due to insufficient braking force when the screw shaft 11 is stopped.
This can be effectively prevented. This is because the driving force control means 25 is installed so as to always function in the advancing direction of the driving rod 13 in FIG. 12, so that the driving rod 13 is pulled by the load of the operation target B to apply a braking force. It is nothing but a good prevention.

Although the present invention has been described with respect to an example in which the electric motor 1 of the driving means 6 is mounted upright on one end of the casing 7, the present invention is not limited to this. It is installed in parallel with the casing 7 on the upper side of the casing 7, and transmits the rotational force of the electric motor 1 to a screw shaft through a reduction gear consisting of a worm and a worm wheel and a pair of bevel gears. When the screw shaft is rotated, the electric motor 1 swingably supports a portion on the opposite side, which is connected to the speed reducing means, when the electric motor 1 is started. When the electric motor 1 is started, the portion that is swingably attached swings, and the impact force generated by the swing is transmitted to the speed reducer → a pair of bevel gears → the screw shaft, so that the screw shaft The present invention is realized even if the tight coupling with the nut is relaxed by the impact force so that the screw shaft can be favorably started.

[0046]

Since the present invention is constructed as described above, it has the following effects. (1) According to the present invention, when the screw shaft of the motion converting means and the drive rod of the output means are drive-connected by the drive force connecting means including a nut, the nut is screw-engaged with the screw shaft at an inner thread portion thereof. However, since the motion converting means and the output means are drive-coupled by being screwed to the drive rod by an outer threaded portion, the load of the operation target applied to the output means depends on the screw between the nut and the drive rod. The whole area of the joint is received and the stress due to the load is distributed to the threaded portion so as not to concentrate at a specific location. It is possible to satisfactorily suppress / avoid the problem that the screw part of the screw concentrates on a specific part of the trapezoidal screw of the screw shaft due to the load and is tightly screwed. It is not necessary to start working to Rukuappu, can be manufactured of this kind of the electric actuator in compact and lightweight.

(2) Further, according to the present invention, when the nut and the driving rod are coupled, the locking piece formed at the open end of the screw portion and the driving rod is engaged with the locking portion recessed on the outer periphery of the nut. Since the drive force connecting means can easily receive the load from the outside because it can be easily attached by simply making it, the drive force connecting means is convenient because it can be assembled quickly and surely with a simple structure.

(3) Further, in the present invention, the driving force control means for controlling the driving of the output means, in combination with the improvement of the driving force connecting means, arbitrarily converts the motion in accordance with the direction of the load applied to the driving rod. Since the electric actuator has a structure that can be installed in a specific place, by changing the mounting position of the driving force control means, the electric actuator can be used in an operation target object in which the direction of the load applied to the driving rod is divided into two directions. Is convenient because it can be dealt with easily.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a state where a drive rod is retracted in an electric actuator of the present invention.

FIG. 2 is a plan view of an electric actuator.

FIG. 3 is a vertical cross-sectional view showing a state where a drive rod is advanced in the electric actuator of the present invention.

FIG. 4 is a cross-sectional view showing a notch of a main part of a speed reducer.

FIG. 5 is a cross-sectional view showing a main part of a one-way clutch.

FIG. 6 is an exploded perspective view showing a driving force connecting means.

FIG. 7 is an explanatory view similarly showing the connection relationship between the nut of the drive force connecting means and the drive rod in an exploded manner.

FIG. 8 is a vertical sectional view showing a state where the driving force connecting means is being assembled.

FIG. 9 is a sectional view of a driving force connecting means.

FIG. 10 is an explanatory diagram showing an application example of the electric actuator.

FIG. 11 is an explanatory diagram showing another application example of the same electric actuator.

FIG. 12 is a vertical cross-sectional view showing a second embodiment of the electric actuator of the present invention.

FIG. 13 is an explanatory diagram of an application example of the electric actuator of the second embodiment.

FIG. 14 is an explanatory view showing a nut and a drive rod constituting a conventional driving force connecting means in an exploded manner.

FIG. 15 is a cross-sectional view showing an assembling process of a conventional driving force connecting means.

FIG. 16 is a cross-sectional view showing an assembled state of a conventional driving force connecting means.

[Explanation of symbols]

1 electric motor 3 deceleration means 6 Drive means 7 casing 9 Motion conversion means 10 trapezoidal screw 11 screw shaft 12 Driving force connecting means 13 Drive rod 18 nuts 19 First screw part 20 screw part 21 Second screw part 23 Locking part 24 Locking piece 25 Driving force control means 26 one-way clutch 30 fixing member A electric actuator

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Claims (3)

(57) [Claims] 1. A drive means for producing a rotary motion, a motion converting means for converting the rotary motion into a linear motion, an output means for outputting the motion converting means and the linear motion converted by the motion converting means are external. The driving force connecting means for dispersing and connecting the load applied from the driving force connecting means, and the driving force control means for controlling the driving force of the output means are disposed in the middle of the driving force connecting means and the motion converting means. And electric actuator. 2. The driving force connecting means has a first screw portion that is screwed into a screw shaft of the motion converting means, and a screw provided inside an open end of a drive rod that serves as output means. A second screw portion that is screwed with the entire area of the
At the end of the threaded part, a nut having a predetermined number of flat locking portions recessed is formed, and a locking piece is provided at the open end of the drive rod that serves as output means corresponding to each locking portion of this nut. Forming a screw shaft of the motion converting means on the first screw portion of the nut,
The drive rods are respectively screwed into the threaded portions of
Fit the locking piece of the drive rod to the locking part on the outer circumference of the nut.
The electric actuator according to claim 1, wherein the motion conversion means and the output means are drivably connected to each other by being fixed. 3. The driving force control means is capable of advancing and retracting the output means in a direction in which the output means is pressed by a load applied to the output means or a direction in which the output means is pulled while applying a braking force to the output means. The electric actuator according to claim 1, wherein the electric actuator is arranged as follows.