JP3133955B2 - Electric cylinder - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric cylinder capable of converting a rotational output of an electric motor into a linear motion and outputting a linear motion equivalent to an air cylinder.

[0002]

2. Description of the Related Art Conventionally, an electric cylinder has been widely used as a mechanism for converting the rotational output of a motor into a linear motion. FIG. 8 is a partial sectional view showing a conventional electric cylinder. The electric cylinder 101 has a configuration in which the rotation output of the drive motor 102 is transmitted to a cylinder unit that outputs a linear motion. In the drive transmission means, a timing belt 105 is stretched between a drive shaft side sprocket 103 and a driven side sprocket 104. The driven sprocket 104 is rotatably supported by the thrust shaft 10.
6 and its thrust shaft 106 has an external thread 10
6a are formed. The male screw 106a is screwed into a female screw 108a of a thrust nut 108, and a thrust rod 109 is coaxially fixed to the thrust nut 108. A coupling 110 is interposed between the thrust rod 109 and the thrust nut 108, and both are screwed and firmly fastened to the coupling 110 to be integrated. The thrust shaft 106 and the thrust rod 109 are covered by a frame 111, and the thrust rod 109 is slidably supported by a bracket 112 and protrudes from the end of the frame 111.

The electric cylinder 1 having such a structure is
In the case of 01, the rotation output is transmitted to the thrust shaft 106 via the timing belt 105 by the drive of the drive motor 102, and the rotation is given to the male screw 106a. When the male screw 106a rotates, the male screw 106a
A thrust is applied to the thrust nut 108 screwed into the nut, and the thrust rod 109 integrated via the coupling 110 moves in the axial direction. The direction of movement is male screw 1
06a.

[0004]

However, in such a conventional electric cylinder 101, since the thrust nut 108 and the thrust rod 109 are both screwed and firmly fastened to the coupling 110, noise is generated. In addition, there has been a problem that heat generation or abnormal wear due to oil film shortage occurs and a sufficient function cannot be exhibited. That is, when the thrust rod 109 and the thrust nut 108 are not formed coaxially or when there is no angle on the fastening surface, the male screw 106a and the female screw 108a mesh only with a part of the plurality of threads. This is to cause a so-called partial hit.

In the conventional electric cylinder 101, a force is often applied to the thrust rod 109 in a lateral direction (hereinafter, referred to as a "radial direction") during a stroke operation. For example, immediately after the new product is manufactured, the parts are accurately machined, so that even if the above-mentioned problem of offset hit does not occur, when the user attaches the electric cylinder 101 to the load machine, the position of the center is adjusted. This is because the attachment may not be performed correctly. Therefore, if a large radial force acts on the thrust rod 109,
Excessive force is applied to the metal bearing 113 and the radial load receiver 114 inside the bracket 112 to accelerate the progress of wear, and the wear is uneven.

Accordingly, if the metal bearing 113 and the radial load receiver 114 are worn by the radial force,
The load machine and the electric cylinder 101 are in a state of so-called blemishes while the center is shifted. In this case, since the thrust rod 109 performs an operation off the center, the engagement between the male screw 106a and the female screw formed on the thrust nut 108 is unbalanced, which also causes abnormal noise, heat generation due to oil film shortage, and the like. This causes a problem that abnormal wear occurs and a sufficient function cannot be exhibited.

[0007] When the electric cylinder 101 is used, the operation of high speed, low speed, and stop is repeated in a normal state of normal operation. However, an abnormality occurs in a load machine on which the electric cylinder 101 operates, or An abnormality may occur in the sensor or control device of the electric cylinder 101. In such a case, a collision may occur in a high-speed state in which the driving torque is applied from the driving motor 102, and an excessive impact force is applied to each component in the electric cylinder 101, which may cause breakage or durability. Is significantly reduced.

In view of the above, an object of the present invention is to provide an electric cylinder capable of preventing an unbalanced screwing of a screw portion between a thrust nut and a thrust shaft and reducing an impact at the time of an abnormality in order to solve such a problem. I do.

[0009]

The electric cylinder according to the present invention has the following structure in order to solve the above-mentioned problems. The electric cylinder of the present invention is a drive motor that provides a rotation output, a thrust shaft including a male screw and rotatably supported in a frame, and a drive transmission unit that transmits the rotation output of the drive motor to the thrust shaft, said thrust shaft flanged <br/> thrust nut having an internal thread to be screwed to the male screw, and a slidably thrust rod which projects axially from said frame by Kutsugae設the external thread The thrust nut extends axially through the flange portion.
Supported by a shoulder bolt fixed to the force rod
Between the flange portion of the thrust nut and the thrust rod.
Between the axial gap, penetration of the flange of the thrust nut
The direction of rotation and radial direction between the hole and the shoulder bolt
It is characterized by having a gap in the direction.

Further, in the electric cylinder according to the present invention, the thrust shaft is fitted to the driving means so as to be movable in an axial direction, and the thrust shaft is rotatably supported in the frame. In addition, the rotary bearing has a rotary bearing provided in the axial direction for sliding support in the axial direction, and an inertia absorbing elastic body mounted between the rotary bearings and absorbing kinetic energy applied to the thrust shaft. Further, the electric cylinder of the present invention has a detector for electronically controlling the rotational position of the drive motor. The electric cylinder according to the present invention includes a position transmitter fixed to the thrust rod, and a position sensor circumscribed in an axial direction of the frame.

The electric cylinder of the present invention having the above-described structure has the following functions and effects. The electric cylinder of the present invention, the rotational output of the driving motor is transmitted to the thrust shaft via the drive transmission means, is to thrust nut rotation of the thrust shaft screwed transmitted as thrust. In other words, the thrust nut is
Since the rotation is limited by the shoulder bolt, thrust
Promote without rotating with the ft. On the other hand, thrust rod
The center of the thrust nut
The rudder bolt has a gap in the rotation direction and the radial direction.
Penetration affects thrust rod centering
The center of the thrust nut and thrust shaft is
Always coincides, preventing unbalance between male and female threads
You. The thrust nut has an axial clearance at the flange.
The thrust rod is tilted even if it tilts
Can follow.

Further, in the electric cylinder according to the present invention, even when the movement of the thrust rod is forcibly stopped, the kinetic energy given to the thrust shaft by the driving means may be applied when the thrust shaft moves in the axial direction. Absorbed by the inertia absorbing elastic body loaded between the rotary bearings, the impact at the time of abnormality is reduced.

[0013]

Next, an embodiment of an electric cylinder according to the present invention will be specifically described. FIG. 1 is a sectional view showing a first embodiment of the electric cylinder. The electric cylinder 1 according to the present embodiment has the same configuration as that of the conventional example in many parts, but details thereof will be described again. The electric cylinder 1 uses a drive motor 2 provided with an NB brake (non-excitation operation type electromagnetic brake) as a drive source, and a drive sprocket 3 is fitted to an output shaft 2a. The output shaft 2a and the driving sprocket 3 are covered by the main body frame 4. On the other hand, in the driven cylinder that receives the rotation output of the drive motor 2, the thrust shaft 5 has ball bearings 6.
6 rotatably supported in parallel with the output shaft 2a. A driven sprocket 7 is fitted to the end,
It is fixed by a ring nut 8. A timing belt 9 for transmitting the rotation output of the drive motor 2 is stretched between the driving sprocket 3 and the driven sprocket 7.

The thrust shaft 5 has a long external thread 5.
The threaded portion formed with a is extended, and the tip 5b is supported by the needle bearing 10. The male screw 5a constitutes a ball screw as described later, and has a spiral U-shaped groove so that the ball held on the female screw 11a side of the thrust nut 11 rolls. The thrust nut 11 and the thrust shaft 5 are screwed together via a ball screw. The thrust nut 11 is formed integrally with the thrust rod 13 via the coupling 12. But,
The thrust nut 11 of the present embodiment has a floating structure, instead of being screwed and firmly fastened to the coupling 12 as in the above-described conventional example.

That is, the thrust rod 13 is connected to the coupling 1
2 is tightly fastened by screwing in the same manner as in the conventional example, while the thrust nut 11 is fitted in a cylindrical thrust nut holder 14 screwed to the coupling 12 in a free state. The dimensions of the thrust nut holder 14 are formed so as to cover the outer diameter and length of the thrust nut 11 larger than the outer diameter and length of the thrust nut 11, so that a gap (hereinafter referred to as a “floating gap”) is formed in the radial direction and the axial direction. Is done. Therefore, the thrust nut 11 is attached to the thrust nut holder 14.
A preload is applied by the disc spring 15 loaded therein, and is pressed by the coupling 12 to be coupled to the thrust rod 13 by a frictional force. Therefore, in the present embodiment, the thrust nut 11 and the thrust rod 13 are configured to operate integrally by frictional force, similarly to the conventional one.

The disc spring 15 is designed to apply a preload exceeding a rated thrust received from a load machine (load), and the positioning accuracy of the thrust nut 11 is maintained. Therefore, the axial gap of the floating gap is
As a result, no apparent gap is generated unless an excessive force exceeding the preload by the disc spring 15 is applied between the thrust nut 11 and the thrust rod 13. On the other hand, the inner peripheral surface of the thrust rod 13 is
The thrust rod 13 is supported by a metal bearing 19 that can slide lightly to the left and right in the drawing. The needle bearing 10 is held in alignment with the thrust shaft 5. In addition, since the thrust rod 13 of the electric cylinder 1 is prevented from rotating by a load machine (not shown), the thrust nut 11 coupled to the thrust rod 13 by frictional force.
Does not rotate.

The force Ff for holding the thrust nut 11 against the force applied in the radial direction is represented by Ff μ1 × preload load × 2 (because frictional resistance occurs on both surfaces of the thrust nut 11). In many cases, the value of the frictional resistance μ1 is about 0.1 between metals, so that the thrust nut 11 is held with a small force of about 1/5 of the preload. Therefore, the thrust nut 11 slides on the friction surface with the coupling 12 by a light force, and can move (float) in the thrust nut holder 14 in the radial direction. Therefore, in the electric cylinder 1 of the present embodiment, even when the center between the external thread 5a of the thrust shaft 5 and the thrust rod 13 is shifted, the external action of the external thread 5a and the internal thread 11a is always caused by the floating action of the thrust nut 11. It is configured to cause sufficient engagement.

On the other hand, the bracket 1 is
6, a cylindrical pipe frame 17 is fixed,
The thrust nut 11, the thrust rod 13, and the thrust shaft 5 are covered. A bracket 18 is also fixed to the end of the pipe frame 17, and the thrust rod 13 is slidably supported through the bracket 18. Further, an annular radial bearing 20 is fitted to the thrust rod 13 and is in contact with the inner peripheral surface of the pipe frame 17. Further, a permanent magnet 21 is attached to the thrust rod 13 in order to detect the output position of the coupling fitting 23 at the tip of the thrust rod 13 protruding from the bracket 18, and the position of the permanent magnet 21 is set at a predetermined position on the outer periphery of the pipe frame 17. Are mounted. Note that rubber cushions 24, 24 are attached to the front and rear brackets 16, 18, for use in the event of an abnormality.

The electric cylinder 1 according to the present embodiment having such a configuration operates as follows. When the output motor 2 is driven and the output shaft 2 a rotates, the rotation of the electric cylinder 1 is transmitted from the driving sprocket 3 to the driven sprocket 7 via the timing belt 9. The rotation output transmitted to the driven sprocket 7 is directly the rotation of the thrust shaft 5. At this time, the rotation given to the thrust shaft 5 is such that the rotational output of the drive motor 2 is reduced and the torque is increased in the driven sprocket 7 by the gear ratio between the driving sprocket 3 and the driven sprocket 7 ( (In some cases, the speed is increased and the torque is reduced.)

The rotated thrust shaft 5 rotates while being supported by the ball bearings 6 and 6 and the needle bearing 10, while its movement in the axial direction is restricted by the ball bearings 6 and 6. When the thrust shaft 5 rotates, the external thread 5a formed thereon also rotates, and when the external thread 5a rotates, the internal thread 1 screwed with the external thread 5a is rotated.
Thrust is applied to the thrust nut 11 having 1a. This is because the thrust nut 11 is configured not to rotate together with the frictional force, so that the rotational force of the male screw 5a is applied to the thrust nut 11 as an axial force by the screw portion.

The rotation of the thrust shaft 5 in a predetermined direction causes the thrust nut 11 to move to the left in the drawing. The thrust of the thrust nut 11 is directly applied to the thrust rod 13. Then, the thrust rod 13 moves in the axial direction,
A linear motion to the left in the drawing is output to the load machine (not shown) connected to the connection fitting 23. If the thrust shaft 5 is reversely rotated, the thrust nut 11 is propelled rightward in the drawing, and the thrust applied to the disc spring 15 pushes the thrust nut holder 14 rightward. Also in this case, since a preload load exceeding the rated thrust is applied to the thrust nut 11 by the disc spring 15, the disc spring 15 does not bend and no gap is left in the axial direction. Then, the thrust rod 13 integrated with the thrust nut holder 14 moves in the axial direction, and a linear motion to the right in the drawing is output to the load machine (not shown) coupled to the coupling fitting 23.

In the case where the connecting fitting 23 is fastened to the load machine, it is difficult in many cases to align the center of the load machine with the center of the thrust shaft 5 over the entire stroke. Therefore, the thrust rod 13 is constantly subjected to a radial force during the reciprocating work, and the metal bearing 19
And the radial bearing 20 will be worn. And
When the wear has stopped and a stable level, that is, a so-called blemishes is present, it means that the wear has progressed to the point where the center between the load machine and the thrust shaft 5 is displaced.

However, even in such a case, in the electric cylinder 1 of the present embodiment, the thrust nut 11 is in a floating state in which the thrust nut 11 is held with a small force in the radial direction with respect to the coupling 12, so that the coupling 12 The meshing between the female screw 11a of the thrust nut 11 and the male screw 5a of the thrust shaft 5 is maintained in good condition only by shifting the position of the thrust nut 11. Also, when the angle of the thrust rod 13 is slightly displaced, the disc spring 15 bends asymmetrically and corrects the deviation of the angle.
Engagement of 1a with the external thread 5a of the thrust shaft 5 is maintained in a good state.

Further, for example, the same applies to a case where the center of the thrust shaft 5 and the thrust rod 13 is displaced or a slight angle is displaced when the machining accuracy of the component is not sufficient. Therefore, when such a center shift or a slight angle shift occurs, in the conventional electric cylinder, the endurance performance of the screw portion causing abnormal noise and abnormal heat is remarkably deteriorated, but the durability of the electric cylinder according to the present embodiment is reduced. In the case of 1, high durability performance can be obtained by good engagement.
In particular, in the electric cylinder, since the engagement portion of the screw determines the durability performance, the electric cylinder 1 can obtain high reliability.

The thrust nut 11 is connected to the thrust rod 1
In this electric cylinder 1 having a floating structure that is coupled by frictional force without being fastened to the
Consider the holding power during First, thrust nut 1
The holding torque Tf of 1 can be expressed as Tf ≒ μ1 × preload load × Rs (radius of contact portion of the disc spring) × 2 ≒ 0.2 × preload load × Rs. Next, in the case of using the ball screw according to the present embodiment, the thrust nut 1 is used in the ball screw portion.
The co-rotating torque Tb applied to 1 is Tb ≒ μ2 × Rated thrust × Rb (ball screw effective radius). Since μ2 ≒ 0.01, the value of Tb is very small.

Although these are represented by approximate values, since the level of RssRb, in the case of the electric cylinder 1, the holding torque Tf of the thrust nut 11 and the co-rotation torque T
The ratio with b is Tf / TbＴ (0.2 × rated thrust × Rs) / (0.01 × rated thrust × Rb) ≒ 20, which indicates that the holding torque Tf of the thrust nut 11 is large. Therefore, the thrust nut 11 does not rotate together with the rotation of the thrust shaft 5. Thrust rod 1
If a load is applied to 3 and the thrust nut 11 generates thrust,
The value of μ1 further increases, and the holding torque Tf increases.

Accordingly, in the electric cylinder 1, during the normal operation, the thrust is applied to the thrust rod 13 without the thrust nut 11 rotating together with the thrust shaft 5. On the other hand, since the holding torque Tf is a finite value, if an abnormal condition occurs and a collision occurs with a partner machine or a workpiece while the vehicle is running at a high speed, the holding torque Tf may be co-rotated with the holding torque Tf and the impact value of the torque Tb may be exceeded. The thrust nut 11 rotates together with the thrust shaft 5 to suppress the impact value to a finite value. For this reason, a torque limiting action that does not apply an excessive load to the thrust shaft 5 is exerted.

By the way, control means (not shown) is connected to the electric cylinder 1, and the rotation of the drive motor 2 is adjusted in response to signals from the magnetic sensors 22 and 22. That is, the thrust rod 13 advances to the left in the drawing, and the permanent magnet 21
An ON signal is transmitted in response to the magnetic sensor 22 at the front end, and rotation of the drive motor 2 is stopped by control means that receives the ON signal, and N provided on the drive motor 2 is provided.
The B brake is actuated to perform positioning. Then, at the time of retreat, a reverse rotation drive signal is sent to the drive motor 2. In order to perform more accurate positioning, although not shown, a deceleration command sensor is newly provided between the magnetic sensors 22 and 22, and an ON signal transmitted in response to the permanent magnet 21 passing therethrough is received. The control signal lowers the rotation speed of the drive motor 2 and stops by the signals of the magnetic sensors 22 and 22.

The electric cylinder 1 is provided with cushions 24, 24 in the pipe frame 17, and when an abnormality occurs and the thrust rod 13 cannot be stopped, the thrust nuts are attached to the cushions 24, 24. Holder 14
Alternatively, the collision of the permanent magnet 21 alleviates a large impact and prevents breakage. Further, since a sufficient clearance is provided between the coupling 12 and the thrust nut holder 14 and the pipe frame 17, even if the radial bearing 20 is worn, the coupling 12 and the thrust nut holder 14 are not removed. There is no contact with the pipe frame 17. In addition, the air in the cylinder moves through the sufficient gap. Although not shown in FIG. 1, the radial bearing 2
The 0 and permanent magnets 21 are also provided with through holes through which air can pass in the axial direction, so that the effect of resistance generated by the back pressure of the air when the thrust rod 13 reciprocates is suppressed.

Next, the second embodiment of the electric cylinder according to the present invention will be described.
Embodiments will be described with reference to the drawings. FIG.
It is sectional drawing which showed the electric cylinder of this Embodiment. The electric cylinder 31 of the present embodiment has a configuration in which a thrust nut is floated similarly to the first embodiment, and the common parts will be briefly described. A rotary encoder 33 is attached to a drive motor 32 of the electric cylinder 31. Therefore, a signal of the rotational position of the drive motor 32 is transmitted electronically, the position of the thrust rod can be confirmed over the entire stroke area, and multiple positions can be determined at an arbitrary position.

The drive motor 32 is a drive sprocket 3
4 is fitted, and a timing belt 36 is stretched between the driven sprocket 35 and the thrust shaft 37. In the electric cylinder 31, the driven sprocket 35 is rotatably supported by a sprocket bearing (ball bearing). A female spline 34a is provided on the inner peripheral surface of the drive-side sprocket 34, while a male spline 37a is provided on the outer peripheral surface of the thrust shaft 37, and both are meshed. Therefore, the rotation of the thrust shaft 37 with respect to the driven sprocket 35 is restricted, and the thrust shaft 37 is free to move in the axial direction. The spline may be a polygonal (hexagonal) slide, a keyed shaft slide, or the like.

The thrust shaft 37 is mounted on the ball bearing 3
A spring 40 that is rotatably supported by the bearings 9 and 39 and that applies a preload is fitted between the ball bearings 39 and 39. The preload by the spring 40 is set to a value equal to or higher than the rated thrust. When the rated thrust is generated in a normal feed operation, the spring 40 enables accurate positioning feed without bending. The ball bearings 39, 39 are configured such that the inner ring and the outer ring can slide together with respect to the axial movement of the thrust shaft 37, and the ball bearings 39, 39 are opposed to each other by the step portion of the thrust shaft 37 and the locking ring. It is configured to slide only on.

On the other hand, the thrust shaft 37 has a male screw 37b.
Is extended, and the tip 37c is supported by the needle bearing 41. Also in the present embodiment, the male screw 37b constitutes a ball screw, and a spiral U-shaped groove is formed so that the ball held on the female screw 42b side of the thrust nut 42 rolls. Therefore, the female screw 42 b of the thrust nut 42 is screwed to the male screw 37 b of the thrust shaft 37.

The thrust nut 42 is formed integrally with a thrust rod 44 via a coupling 43. A thrust rod 44 is screwed into the coupling 43 so as to be firmly fastened, while the thrust nut 42 is preloaded by a disc spring 46. That is, the thrust nut 42 of the present embodiment has a floating structure as in the case of the first embodiment. by the way,
In the present embodiment, the thrust nut 42 and the coupling 43
A detent is provided between them. Thrust nut 4
A pin 47 is fixed to the friction surface of
Is formed with a pin hole 43a into which the pin 47 can be inserted in a non-contact state.

The inner peripheral surface of the thrust rod 44 is loosely fitted with the outer peripheral surface of the needle bearing 41.
On the other hand, a bracket 49 is fitted to the end of the frame 48, and the thrust rod 44 is supported by a metal bearing 50. Further, a permanent magnet 52 is attached to the thrust rod 44 to detect the movement origin position of the thrust rod 44, and a magnetic sensor 53 for detecting the position of the permanent magnet 52 is attached to a predetermined position on the outer periphery of the frame 48. ing.
And rubber cushions 54, 54 are attached as stoppers. A thrust value transmitting magnet 55 for detecting the axial movement of the thrust shaft 37 is fixed to the end of the thrust shaft 37 in the electric cylinder 31, and the position of the thrust value transmitting magnet 55 is detected in the cover 58. The magnetic sensor 56 is mounted.

The electric cylinder 1 according to the present embodiment having such a configuration operates as follows. The rotation of the electric cylinder 31 whose rotation angle is controlled by the signal of the rotary encoder 33 is output and transmitted to the thrust shaft 37. The rotation of the thrust shaft 37 is transmitted to the thrust nut 42 as thrust, and the coupling metal fitting 51 at the tip of the thrust rod 44 to be propelled is positioned. by the way,
The electric cylinder 31 is provided with a pin 47 for preventing rotation between the thrust nut 42 and the coupling 43, but the thrust nut 42 normally has a force exceeding the rated thrust due to the preload of the disc spring 46. Since it is hung, it is propelled without rotating together with the thrust shaft 37.

As described above, the rotation of the drive motor 32 propels the thrust nut 42 and outputs a linear motion to a load machine or the like. However, when an abnormality occurs and a collision occurs during high-speed operation, the thrust rod 44 Linear motion is forcibly stopped. The thrust nut 42 co-rotates with the thrust shaft 37 because movement in the axial direction is restricted, and the coupling 4
The sliding surface is rotated by a predetermined amount and stopped by the pin 47 hitting the side surface of the pin hole 43a. On the other hand, the thrust shaft has a driving torque of the driving motor 32,
A kinetic energy stored in the drive system produces a force for further rotation.

Therefore, the electric cylinder 31 of the present embodiment
Since the thrust shaft 37 is supported by ball bearings 39, 39 sliding in the axial direction, the thrust shaft 37 is screwed in the thrust nut 42. At this time, the thrust shaft 37 moves in the axial direction by the number of revolutions and the screw lead, so that one of the ball bearings 39 is pushed and the spring 40 is bent. When the thrust shaft 37 moves in the axial direction, the magnetic sensor 56 transmits an ON signal in response to the movement of the thrust value transmitting magnet 55, and the drive motor 32 is turned off.
F, and the NB brake is applied and stops.

Therefore, when a collision occurs with a partner machine or a workpiece while the vehicle is running at a high speed, the impact force of each part caused by the restriction of the movement of the thrust rod 44 is absorbed by the spring 40 which is an inertia absorbing elastic body. Thereby, the peak value of the impact force is suppressed. Therefore, while the drive motor 32 is being driven, the thrust shaft 37 and the thrust nut 4
Even when the continuous transmission of power to the power transmission 2 is interrupted, the rotation of the thrust shaft 37 is consumed as a spiral motion,
The pin 47 for preventing rotation is not damaged, and the load on each power transmission mechanism is reduced, so that damage is avoided.

The electric cylinder 31 can perform not only positioning but also pressing (pulling) operation. That is, the rotation angle of the drive motor 32 is controlled by the signal of the rotary encoder 33, approaching the work at high speed, switching to low speed torque when approaching, pushing (pulling) the thrust rod 44 against the work, and applying the drive torque as it is. The thrust rod 44 stops due to the reaction force received from the work,
As described above, the thrust shaft 37 moves in the axial direction to deflect the spring 40. The magnetic sensor 56 that responds to the thrust value transmitting magnet 55 in a predetermined bending state transmits an ON signal. The NB brake is applied first by the ON signal, and the drive motor 32 is turned off and stopped after the brake is activated. In this state,
The thrust rod 44 is pressed (pulled) against the work by the elastic expansion force of the spring 40 to restore, and a thrust force (pulling) is generated by the elastic force of the elastic body even when no current is supplied.

In the present electric cylinder 31, similarly to the first embodiment, the thrust nut 42 having a floating structure urged by the disc spring 46 has a thrust rod 44 whose radial direction extends from the load machine in the radial direction. Even if a force is applied, the coupling between the female screw 42b and the male screw 37b is maintained in a good state only by the coupling 43 being displaced from the thrust nut 42. Therefore, even if the center between the load machine and the thrust shaft 37 is shifted, the ball screw between the thrust nut 42 and the thrust shaft 37 is biased by correcting the angle shift by distorting the disc spring 46 asymmetrically. Smooth thrust is generated without getting up and twisting. Therefore, high durability performance and high reliability can be obtained by good engagement.

In the present embodiment, the pin 47 is inserted in the floating state into the pin hole 43a, but an O-ring 61 for alignment may be fitted as shown in FIG. This is because the rotation angle is controlled by the signal of the rotary encoder 33, so that the thrust nut 42 slides in the rotation direction due to the impact, so that the displacement does not occur in the rotation direction. When a displacement occurs due to a collision, a slight deviation occurs in the positioning by the signal of the rotary encoder 33 before and after the collision. Therefore, when the thrust nut 42 is displaced in the rotation direction, the pin 47 is pushed back by the elastic force of the O-ring 61 to return to the center, thereby performing accurate positioning.

Next, a third embodiment of the electric cylinder according to the present invention will be described.
An embodiment will be described. FIG. 4 is a cross-sectional view illustrating the electric cylinder according to the present embodiment. The electric cylinder 71 of this embodiment has the same basic structure as that of the second embodiment, and uses the magnetic sensor adopted in the first embodiment instead of the rotary encoder 33 for positioning the thrust rod. It is. Therefore, in the drawings, the same components are denoted by the same reference numerals, and description thereof will be omitted. The feature of this embodiment lies in the thrust nut 72.
The thrust nut 72 of the present embodiment has a flanged shape, and a pin hole 72c penetrating in the axial direction is formed in a part of the flange portion 72a. The thrust nut 72 forms a female screw 72 b holding a ball on the inner peripheral surface, and is screwed with the male screw 37 b of the thrust shaft 37.

The thrust nut 72 is connected to the thrust rod 4
Coupling 73 with fixed 4 and thrust nut holder 7
4. Thrust nut holder 74
A pin 75 fixed to the coupling 73 and protruding is inserted into a pin hole 72 c of the thrust nut 72. Also,
The thrust nut 72 is a flange portion 72a of the thrust nut 72.
A small gap a is formed between the coupling and the coupling 73. The pin 75 of the thrust nut holder 74 is
c to allow the thrust nut 72 to shift in the rotational direction and the radial direction. Thus, in such an electric cylinder 71, when the male screw 37 b of the thrust shaft 37 rotates, the rotational force is transmitted to the female screw 72 b screwed to the thrust shaft 37. Rotation is limited. Therefore, the thrust nut 72 is propelled, and a linear motion is output from the thrust rod 44.

Therefore, the electric cylinder 71 of the present embodiment
According to the above, even if the thrust rod 44 is displaced from the center, the thrust of the pin 75 of the thrust nut holder 74 is loosely fitted with a gap that allows the displacement of the thrust nut 72 in the rotation direction and the radial direction. Female screw 7 of nut 72
Engagement between 2b and the external thread 37b of the thrust shaft 37 is maintained in a good state. Also, even if the angle of the thrust rod 44 shifts by a small amount, the thrust nut 72 is inclined between the small gaps a to correct the angle shift, so that the female screw 72b of the thrust nut 72 meshes with the male screw 37b of the thrust shaft 37. Is kept in a good condition. Further, the peak value is suppressed by absorbing the impact force at the time of abnormality by the spring 40,
The burden on each power transmission mechanism is reduced. Moreover, in the electric cylinder 71 of the present embodiment, the thrust nut 72 is selected from the most commercially available shape, so that the cost can be reduced.

Next, a fourth embodiment according to the electric cylinder of the present invention will be described.
An embodiment will be described. FIG. 5 is a partial cross-sectional view showing the electric cylinder of the present embodiment. The electric cylinder according to the present embodiment has a basic structure similar to that of the third embodiment. Thus, with the same reference numerals in the same configuration in the drawings, the description of have other configurations Nitsu omitted. The feature of the present embodiment lies in the thrust nut 77 and its supporting method. The thrust nut 77 of the present embodiment has a flanged shape, and a through hole 77c penetrating in the axial direction is formed in the flange portion 77a. The thrust nut 77 forms a female screw 77b holding a ball on the inner peripheral surface, and is screwed with the male screw 37b of the thrust shaft.

A coupling 76 is fixed to the thrust rod 44, and the thrust nut 77 is supported by a shoulder bolt 78 fixed to the coupling 76 penetrating through the through hole 77c. In this case, similarly to the third embodiment, the thrust nut 7
A small gap a is provided in the flange portion 77a in the axial direction in the flange portion 77, and a gap is provided in the through hole 77c between the shoulder portion 78 and the shoulder bolt 78 so as to allow displacement in the rotation direction and the radial direction of the thrust nut 77. . Therefore, in such an electric cylinder, the rotation of the external thread 37b of the thrust shaft transmits the rotational force to the internal thread 77b screwed thereto, but the thrust nut 78 is fixed by the shoulder bolt 78 fixed to the coupling 76. The rotation of 77 is limited. Therefore, the thrust nut 77 is propelled, and pushing (or pulling) the coupling 76 outputs a linear motion from the thrust rod 44.

Therefore, according to the electric cylinder of the present embodiment, even if the thrust rod 44 is displaced from the center, the shoulder bolt 78 has a clearance enough to allow the displacement of the thrust nut 77 in the rotation direction and the radial direction. Because of the loose fit, the good engagement between the female screw 77b of the thrust nut 77 and the male screw 37b of the thrust shaft 37 is maintained. Even if the angle of the thrust rod 44 is displaced by a small amount, the engagement between the female screw 77b of the thrust nut 77 and the male screw 37b of the thrust shaft is attained by correcting the deviation of the angle by tilting the thrust nut 77 between the small gaps a. Good condition is maintained. In the electric cylinder 71 according to the present embodiment, the thrust nut 77 is selected from the most commercially available shape, so that the cost can be reduced.

Next, the fifth embodiment according to the electric cylinder of the present invention will be described.
An embodiment will be described. FIG. 6 is a sectional view of a thrust nut portion showing the electric cylinder according to the present embodiment. The electric cylinder according to the present embodiment urges a thrust nut 81 provided in a thrust nut holder 84 to a coupling 83 by a disc spring 82 to provide a friction surface with a friction surface, similarly to the electric cylinder shown in the first embodiment. They are connected by the generated frictional force. However, in the present embodiment, the splines 81a, 8 formed on the thrust nut 81 and the thrust nut holder 84 are provided.
4a, two resistance plates 85, 85, 86,
86 are stacked alternately. The resistance plate 85 is shown in FIG.
As shown in (a), a tooth pattern is formed on the inner periphery, and the resistance plate 86 is formed.
As shown in FIG. 7 (b), a tooth pattern is formed on the outer periphery and meshes with splines 81a and 84a, respectively.

Therefore, these resistance plates 85, 85, 86,
86 is also urged in the axial direction by the urging member. For this reason, in the first embodiment, the friction surfaces are two surfaces of the thrust nut 11 and the coupling 12, but are increased to six surfaces, and the holding torque of the thrust nut 81 is increased. Therefore, in the present embodiment, the same effects as those of the first embodiment are obtained, and the frictional resistance of the friction surface is increased, for example, when a slide screw is used for the threaded portion between the thrust nut 81 and the thrust shaft 87. It is effective when it is desired. When the friction resistance is changed, the number of friction surfaces may be changed by arbitrarily setting the number of resistance plates.

Although the embodiments of the electric cylinder according to the present invention have been described above, the present invention is not limited to these, and various modifications can be made without departing from the gist of the present invention. In the first embodiment, the positioning of the thrust nut 11 in the floating state is performed using the disc spring 15, but another urging member, for example, an elastic material such as rubber may be inserted. Further, the thrust nut 11 is urged toward the thrust rod 13 by an urging member such as a disc spring. However, the thrust nut 11 may be inserted into the opposite side to urge in the opposite direction, or may be inserted into both sides. You may make it.

For example, when a ball screw is used, the frictional resistance of the friction surface between the thrust nut and the coupling is reduced in order to reduce the impact at the time of abnormality, or when a slide screw is used, the holding force is reduced. It may be desired to increase the frictional resistance of the friction surface in order to increase the torque. In such a case, a resin sheet that changes the friction coefficient may be inserted into the friction surface. In addition, the second
In the third embodiment, a pin is used for the rotation stop. However, a stud bolt having a rotation stop function may be used, or a stud bolt having a protrusion and a recess fitted to each other may be formed. Further, in the above-described embodiment, the magnetic sensor is used for detecting the position of the thrust rod, but other optical or mechanical types may be used.

[0053]

According to the present invention, there is provided a drive motor for providing a rotational output, a thrust shaft provided with a male screw and rotatably supported in a frame, a drive transmitting means for transmitting the rotational output of the drive motor to the thrust shaft, has a flanged thrust nut having an internal thread to be screwed to the external thread of the thrust shaft and a thrust rod which projects freely in the axial displacement from the frame by Kutsugae設an external thread, the thrust nut, flange Department
Sholes fixed to axially penetrating thrust rods
It is supported by Daboruto, flange portion and estimation of the thrust nut
The axial clearance between the force rod and the thrust nut
Between the through hole in the flange and the shoulder bolt.
With a clearance in the radial direction, the thrust nut and thrust
Thrust rod can be prevented from unbalanced screwing with the shaft.
The biasing member tilts and flexes even if the
It is possible to provide an electric cylinder that can follow the runout
It became.

According to the present invention, the thrust shaft is fitted to the driving means so as to be movable in the axial direction.
An axially mounted rotary bearing that rotatably supports the thrust shaft within the frame and slides and supports in the axial direction, and an inertia absorbing elastic body that is mounted between the rotary bearings and absorbs kinetic energy applied to the thrust shaft. Therefore, when the movement of the thrust rod is forcibly stopped, the kinetic energy given to the thrust shaft by the driving means is reduced by the inertia loaded between the rotary bearings when the thrust shaft moves in the axial direction. It has become possible to provide an electric cylinder which is absorbed by the absorbing elastic body and in which the impact at the time of abnormality is reduced.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a first embodiment of an electric cylinder according to the present invention.

FIG. 2 is a sectional view showing a second embodiment of the electric cylinder according to the present invention.

FIG. 3 is an enlarged sectional view showing a rotation preventing portion of a thrust nut.

FIG. 4 is a sectional view showing a third embodiment of the electric cylinder according to the present invention.

FIG. 5 is a partial sectional view showing a fourth embodiment of the electric cylinder according to the present invention.

FIG. 6 is a sectional view of a thrust nut part showing an electric cylinder according to a fifth embodiment of the present invention.

FIG. 7 is a view showing a resistance plate.

FIG. 8 is a sectional view showing a conventional electric cylinder.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Electric cylinder 2 Drive motor 5 Thrust shaft 5a Male screw part 11 Thrust nut 11a Male screw 12 Coupling 13 Thrust rod 14 Thrust nut holder 15 Disc spring 21 Permanent magnet 22 Magnetic sensor

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Ito ▲ Shin ▼ 3005 Hayasaki, Kita-gaiyama, Komaki City, Aichi Prefecture Inside CKD Corporation (56) References JP-A-63-251144 (JP, A) 1-127245 (JP, A) JP-A-61-211567 (JP, A) JP-A-8-90380 (JP, A) JP-A-1-116730 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H02K 7/06

Claims (4)

(57) [Claims] A drive motor for providing a rotational output; a thrust shaft having an external thread and rotatably supported in a frame; a drive transmitting means for transmitting a rotational output of the drive motor to the thrust shaft; off with an internal thread to be screwed to the external thread of the shaft
A thrust nut with a flange , and a thrust rod that covers the external thread and is slidably protruded in the axial direction from the frame, and the thrust nut penetrates the flange portion in the axial direction.
Supported by a shoulder bolt fixed to the thrust rod
Between the flange portion of the thrust nut and the thrust rod.
Between the axial gap, penetration of the flange of the thrust nut
The direction of rotation and radial direction between the hole and the shoulder bolt
An electric cylinder characterized by having a gap in the direction. 2. The electric cylinder according to claim 1,
The thrust shaft is moved in the axial direction with respect to the driving means.
The thrust shaft is rotatably supported in the frame.
As well as installed in the axial direction to support sliding in the axial direction
A rotary bearing and a load between the rotary bearing and the thrust shaft
Having an inertia absorbing elastic body that absorbs kinetic energy
An electric cylinder characterized by the following. 3. The electric series according to claim 1 or 2, wherein
A drive motor for electronically controlling the rotational position of the drive motor.
An electric cylinder having an output device. 4. according to any one of claims 1 to 3
In the electric cylinder, the position transmitter fixed to the thrust rod and the frame
And a position sensor circumscribed in the axial direction of the system.
Electric cylinder