JP4401242B2 - Electric linear actuator - Google Patents

Description

The present invention relates to an electric linear actuator, and more particularly to an electric linear actuator including a ball screw that operates frequently with a short stroke.
Here, the short stroke is a stroke used for pressurization such as an injection part drive mechanism of an electric injection molding machine or a press part drive mechanism of an electric press machine, and the stroke is a nut constituting a ball screw. Is less than about 2.2 times the total length.

Conventionally, as an example of an electric linear actuator provided with a ball screw that operates frequently with a short stroke, there is one used for an injection part drive mechanism of an electric injection molding machine or a press part drive mechanism of an electric press machine.
The ball screw of this electric linear actuator supplies a lubricating oil over a long period of time to the friction surface between the balls while interposing a spacer made of a solid lubricating composition between the balls to avoid a decrease in load capacity. (For example, refer to Patent Document 1).
JP 2001-317605 A

However, the electric linear actuator provided with the ball screw disclosed in the above-mentioned Japanese Patent Application Laid-Open No. 2001-317605 has a spacer made of a solid lubricant composition interposed between the balls in order to withstand a high frequency operation with a short stroke. A ball screw is used.
However, when the ball screw reaches the end of its life even though other parts are still usable, there is a problem that only the ball screw cannot be replaced with a new one.
If a general ball screw is used for an electric linear actuator that operates frequently with a short stroke, the general ball screw often reaches the end of its life, and other parts can still be used. Nevertheless, there is a problem that the entire electric linear actuator must be replaced with a new one.

  Therefore, the present invention solves the problems of the prior art, that is, the object of the present invention is to replace the ball screw by detachably installing it as a ball screw unit to the final stage wheel of the speed reduction mechanism. It is possible to provide an electric linear actuator that can use a general ball screw.

  In order to solve the above-mentioned problems, a first aspect of the present invention provides a gear case incorporating a speed reduction mechanism, an electric motor attached to the gear case, a bracket removably attached to the gear case, and a screw attached to the bracket. And a screw shaft case that is detachably attached and incorporates a ball screw, and one end of a nut constituting the ball screw is connected to the final wheel constituting the speed reduction mechanism so as not to be rotatable relative to the axial direction and separable in the axial direction. The other end of the nut is supported in the bracket by a rolling bearing capable of receiving a thrust load, and the rolling bearing on the opposite side to the nut of the pair of rolling bearings supporting the final stage wheel. Is constituted by a rolling bearing capable of receiving a thrust load, and the rotation of the nut constitutes a ball screw. An electric linear actuator that is converted into a linear motion in the axial direction of the same shaft and used in a state in which a thrust load is applied to the screw shaft, and a rolling bearing that supports the ball screw and the nut; A ball bearing presser that applies pressure to the rolling bearing by the screw-in amount of the screw shaft case is detachably incorporated when the ball screw is exchanged with respect to the final wheel constituting the speed reduction mechanism and the bracket attached to the gear case. It constitutes a screw unit.

  In order to solve the above-mentioned problem, the invention according to claim 2 is characterized in that, in addition to the configuration of the electric linear actuator according to claim 1, the screw shaft case is screwed into the bracket so that the end surface of the screw shaft case becomes a bearing retainer. The preload of the rolling bearing is adjusted by the screwing amount of the screw shaft case. The preload is applied to the rolling bearing through the bearing retainer.

According to the first aspect of the present invention, one end of the nut constituting the ball screw is connected to the final stage wheel constituting the speed reduction mechanism so as not to be relatively rotatable and separable in the axial direction, and the rolling bearing supports the ball screw and the nut. The ball screw unit is configured with the bearing retainer that applies pressure to the rolling bearing with the screw shaft case screw-in amount, and the ball screw unit is detachably incorporated into the final stage wheel and bracket. Can be easily replaced.
Moreover, since the ball screw which comprises a ball screw unit can be replaced | exchanged easily, a general ball screw can be used for an electric linear actuator provided with a ball screw which operates frequently with a short stroke.

  According to a second aspect of the present invention, the screw shaft case is screwed into the bracket so that the end surface of the screw shaft case presses the side surface of the bearing retainer and preloads the rolling bearing via the bearing retainer. In addition, since the preload of the rolling bearing is adjusted by the screwing amount of the screw shaft case, when the ball screw unit is detachably assembled to the final stage wheel and the bracket, the preload applied to the rolling bearing can be easily obtained. Can be adjusted.

A gear case with a built-in reduction mechanism, an electric motor attached to the gear case, a bracket detachably attached to the gear case, a screw shaft case detachably attached to the bracket by screwing, a gear case, a bracket, and a screw shaft A ball screw built in the case, and one end of a nut constituting the ball screw is coupled to a second stage wheel (final stage wheel) constituting a speed reduction mechanism so as not to be relatively rotatable and axially separable. The other end of the bearing is supported in the bracket by a tapered roller bearing, and the rolling bearing on the opposite side to the nut of the pair of rolling bearings supporting the second stage wheel (final stage wheel) is configured by a tapered roller bearing. The rotation is converted into the linear motion in the axial direction of the screw shaft that constitutes the ball screw, and a thrust load is applied to the screw shaft. An electric linear actuator used in a state where a ball screw unit is composed of a tapered roller bearing supporting a ball screw and a nut and a bearing retainer, and the ball screw unit is a second stage wheel (last stage wheel) and A tapered roller bearing and a second roller bearing that is removably assembled to the bracket, and the screw shaft case is screwed into the bracket so that the end surface of the screw shaft case presses the side of the bearing retainer and supports the other end of the nut via the bearing retainer. A preload is applied to a tapered roller bearing that supports a two-stage wheel (final stage wheel), and the preload of both tapered roller bearings is adjusted by the screwing amount of the screw shaft case.
Examples thereof will be described below.

An embodiment of the present invention will be described below with reference to FIGS.
As shown in FIG. 1, an electric linear actuator according to an embodiment of the present invention includes a gear case 1 incorporating a speed reduction mechanism, an electric motor 8 attached to the gear case 1, and a bracket detachably attached to the gear case 1. 9, a screw shaft case 12 detachably attached to the bracket 9 by screwing, a gear case 1, a bracket 9, and a ball screw 14 built in the screw shaft case 12.

The gear case 1 includes a gear case main body 1a and a cover 1b, and a reduction mechanism is built in the gear case 1.
Such a speed reduction mechanism includes a first stage pinion 2, a first stage wheel 3 that meshes with the first stage pinion 2, a second stage pinion 4, and a second stage wheel that meshes with the second stage pinion 4 (final stage). A wheel 5 is supported in the gear case 1 by a pair of rolling bearings.
In this embodiment, one of the pair of rolling bearings supporting the second stage wheel (final stage wheel) 5, that is, the rolling bearing on the side opposite to the nut 16 constituting the ball screw 14 as will be described later. The tapered roller bearing 6 is used so that it can receive much thrust load.
An angular ball bearing may be used instead of the tapered roller bearing 6.
Further, the through hole of the gear case main body 1a through which the end of the second stage wheel (final stage wheel) 5 passes and the through hole of the cover 1b through which the shaft part 15a of the screw shaft 15 constituting the ball screw 14 passes are provided. Oil seals 7 for preventing leakage of lubricant such as grease in the gear case 1 are mounted.

  An electric motor 8 is attached to the side surface of the gear case main body 1a, and the motor shaft 8a of the electric motor 8 is connected to the shaft of the first stage pinion 2 by key connection.

A substantially cylindrical flanged bracket 9 is detachably attached to the side surface of the gear case main body 1a by a plurality of hexagon socket bolts 10.
An inward flange portion 9b is formed at the end of the bracket 9 opposite to the flange 9a, and a female screw 9c is formed at the inner diameter portion of the flange portion 9b.

A cylindrical and bottomed screw shaft case 12 having a screw 12a formed on the outer diameter side of one end is screwed into a female screw 9c of a collar portion 9b of the bracket 9, and is detachably attached to the bracket 9. ing.
A lock nut 13 is attached to the male screw 12 a of the screw shaft case 12.

The ball screw 14 is a general ball screw, and includes a screw shaft 15 having a spiral groove formed on the outer peripheral surface, a nut 16 having a spiral groove formed on the inner peripheral surface, and a plurality of screws interposed between the spiral grooves. Ball (not shown).
As for the screw shaft 15, the shaft part 15a is integrally provided in the front end side, the screw part is provided in the rear end side, and the stopper nut 15b is screwed into this screw part.
The stopper nut 15b has a stopper function for preventing the tapered roller bearing 18 and the bearing retainer 19 constituting the ball screw unit 20 described later from coming out.
In this embodiment, one end of the nut 16 is connected to the end of the second stage wheel (final stage wheel) 5 constituting the speed reduction mechanism by the single round key 17 so as not to be relatively rotatable and separable in the axial direction. The other end of 16 is supported in the bracket 9 by a tapered roller bearing 18.
In the present embodiment, the tapered roller bearing 18 is used so that a large thrust load can be received.
An angular ball bearing may be used instead of the tapered roller bearing 18.
Then, the rotation of the nut 16 by the second stage wheel (final stage wheel) 5 is converted into a linear motion of the screw shaft 15 in the axial direction.
The electric linear actuator is used in a state where a thrust load is applied to the screw shaft 15.

The ball screw 14 is built in the gear case 1, the bracket 9 and the screw shaft case 12.
Further, as shown in FIG. 2, the ball screw 14, the tapered roller bearing 18 that supports the other end of the nut 16, and the end face of the tapered roller bearing 18 for applying preload to the tapered roller bearing 6 and the tapered roller bearing 18. A ball screw unit 20 is constituted by a disk-shaped bearing retainer 19 arranged on the side.
As will be described later, the ball screw unit 20 is detachably incorporated in the second stage wheel (final stage wheel) 5 by removing the bracket 9 and the screw shaft case 12 from the gear case body 1a.

Below, the case where the electric linear actuator of a present Example is used as a press part drive mechanism of an electric press machine is demonstrated, for example.
The cover 1b constituting the gear case 1 of the electric linear actuator is attached to the frame P (see FIGS. 3 to 8) of the press drive mechanism of the electric press machine, and the tip of the shaft 15a of the screw shaft 15 constituting the ball screw 14 is mounted. A die (not shown) is attached via a single-round key 21.

Next, the operation of the electric linear actuator when the electric linear actuator of the present embodiment is used as a press portion drive mechanism of an electric press machine will be described.
When the electric motor 8 is rotated in the forward direction, the rotation of the motor shaft 8a is decelerated to the second stage wheel (final stage wheel) 5 via the first stage pinion 2, the first stage wheel 3, and the second stage pinion 4. The nut 16 connected to the end of the second stage wheel (final stage wheel) 5 so as to be relatively non-rotatable and separable in the axial direction is rotated by the single-round key 17, and the rotation of the nut 16 is screwed. The shaft 15 is converted into an axial movement, and the screw shaft 15 is lowered.
When the screw shaft 15 is lowered, a die (not shown) attached to the tip of the shaft portion 15a of the screw shaft 15 is lowered together with the screw shaft 15 and press working is performed.
At the time of press working due to the lowering of the screw shaft 15, a thrust load is applied in a direction in which the screw shaft 15 is pushed into the screw shaft 15, and this thrust load is a tapered roller bearing that supports the nut 16 via the nut 16. 18 is accepted.
When the screw shaft 15 is lowered to the bottom dead center, the electric motor 8 is rotated in the reverse direction, and the screw shaft 15 is raised and returned.
Thus, the electric linear actuator of the present embodiment performs press working by moving the screw shaft 15 up and down by a short stroke with high frequency.

The description of the operation of the electric linear actuator described above is for the case where a thrust load is applied in the direction of pushing the screw shaft 15 against the screw shaft 15 during press working. The linear actuator can also be applied when a thrust load is applied in the direction in which the screw shaft 15 is pulled with respect to the screw shaft 15 during press working.
In this way, when a thrust load in the direction of pulling the screw shaft 15 is applied to the screw shaft 15 during press working, the thrust load is transmitted via the nut 16 and the second stage wheel (final stage wheel) 5. It is received by a tapered roller bearing 6 that supports a second stage wheel (final stage wheel) 5.

By the way, if the electric linear actuator is used under the condition that it is frequently operated with a short stroke, as described above, the ball screw 14 may reach the end of its life even though other parts are still usable. .
In particular, in an electric linear actuator equipped with a general ball screw 14, the ball screw 14 often reaches the end of its life first.
In such a case, it is reasonable to replace only the ball screw 14 that has reached the end of its life.

  Therefore, in the electric linear actuator of the present embodiment, the nut 16 is provided at the end of the second stage wheel (final stage wheel) 5 in order to enable replacement of the ball screw 14, that is, replacement. The ball screw 14, the tapered roller bearing 18, and the bearing retainer 19 constitute a ball screw unit 20 that is not rotatable relative to each other and can be separated in the axial direction. The ball screw unit 20 is a second stage wheel (final stage wheel). 5 and the bracket 9 are detachably incorporated.

  Next, replacement of the ball screw unit 20, that is, attachment / removal procedures will be described below with reference to FIGS.

To remove the ball screw unit 20 from the electric linear actuator, first, as shown in FIG. 3, the lock nut 13 is loosened, and then the female screw 9c of the bracket 9 and the male screw 12a of the screw shaft case 12 are screwed together. The screw shaft case 12 is removed from the bracket 9 in the direction of the arrow in FIG.
Next, as shown in FIG. 4, the hexagon socket head cap bolt 10 is removed together with the seal washer 11, and the bracket 9 is removed from the gear case body 1a in the direction of the arrow in FIG.
Further, in order to take out the ball screw unit 20, the attachment to the mold (not shown) is removed, and taping is performed on the attachment screw portion at the tip of the shaft portion 15 a of the screw shaft 15.
Next, as shown in FIG. 5, the nut 16 is separated from the second stage wheel (final stage wheel) 5 in the axial direction, and the ball screw unit 20 is moved from the second stage wheel (final stage wheel) 5 to the arrow in FIG. Pull out in the direction.

  Next, the ball screw 14 which has reached the deterioration or life of the removed ball screw unit 20 is replaced with a new ball screw 14.

In order to attach the ball screw unit 20 replaced with the new ball screw 14 to the electric linear actuator, first, as shown in FIG. 6, the single round key 21 at the tip of the shaft portion 15a of the screw shaft 15 is once removed and the oil Tap the seals 7 and 7 so as not to damage them. In addition, a one-round key 17 is attached to one end of the nut 16.
A single round key 17 attached to one end of the nut 16 is inserted in the direction of the arrow in FIG. 6 in accordance with the phase of the keyway of the second stage wheel (final stage wheel) 5, and the ball screw unit 20 is inserted into the second stage wheel (final stage wheel). The second stage wheel (final stage wheel) 5 is connected to the second stage wheel (final stage wheel) 5 so as not to be relatively rotatable and separable in the axial direction (see FIG. 7).
At this time, the nut 16 is moved toward one side (upward) so that a ball (not shown) does not fall off from the nut 16 of the ball screw unit 20.
Next, as shown in FIG. 7, the tape taped at the tip of the shaft portion 15 a of the screw shaft 15 is removed, and a single-round key 21 is attached to the tip of the shaft portion 15 a of the screw shaft 15 to mold the electric press machine ( (Not shown).
Then, the bracket 9 is moved in the direction of the arrow in FIG. 7, and the hexagon socket head bolt 10 is screwed into the gear case body 1a together with the seal washer 11, and the bracket 9 is attached to the gear case body 1a (see FIG. 8).
At this time, a slack preventing agent is applied to the hexagon socket head cap bolt 10 in advance.
Next, as shown in FIG. 8, the lock nut 13 is passed through the screw shaft case 12, the screw shaft case 12 is moved in the direction of the arrow in FIG. 8, the rear end portion of the screw shaft 15 is covered, The male screw 12a at the tip of the screw shaft case 12 is screwed into 9c.
When the screw shaft case 12 is screwed into the bracket 9, the end surface of the tip of the screw shaft case 12 presses the side surface of the bearing retainer 19 and supports the second stage wheel (final stage wheel) 5 through the bearing retainer 19. A certain preload is applied to the tapered roller bearing 18 that supports the tapered roller bearing 6 and the nut 16.
The preload of the tapered roller bearing 6 and the tapered roller bearing 18 is adjusted by the screwing amount of the screw shaft case 12.
Finally, after adjusting the preload of the tapered roller bearing 6 and the tapered roller bearing 18, the lock nut 13 is securely tightened with a key spanner or the like to fix the screw shaft case 12 (see FIG. 1).

The present embodiment configured as described above has the following effects.
One end of the nut 16 constituting the ball screw 14 is connected to the second stage wheel (final stage wheel) 5 constituting the speed reduction mechanism so as not to be relatively rotatable and separable in the axial direction, and supports the ball screw 14 and the nut 16. The tapered roller bearing 18 and the bearing retainer 19 constitute a ball screw unit 20, and the ball screw unit 20 is detachably mounted on the second stage wheel (final stage wheel) 5 and the bracket 9, and the second stage wheel (final stage) Since the preload of the tapered roller bearing 6 supporting the stepped wheel 5 and the tapered roller bearing 18 supporting the nut 16 can be easily adjusted, the ball screw 14 constituting the ball screw unit 20 can be easily replaced.
Therefore, the economical efficiency and maintainability of the device on which the electric linear actuator is mounted can be improved and the cost can be reduced.
Moreover, since the ball screw 14 which comprises the ball screw unit 20 can be replaced | exchanged easily, a general ball screw can be used for the electric linear actuator provided with the ball screw 14 which operates frequently with a short stroke.
Therefore, it is easy to obtain the merit of electrification.
Advantages of electrification include long life of the mold and 24-hour operation due to controllability, oillessness, low noise, etc.

  In the present embodiment, one end of the nut 16 is connected to the second stage wheel (final stage wheel) 5 constituting the speed reduction mechanism by the single round key 17 so as not to be relatively rotatable and separable in the axial direction. In the first and second aspects of the present invention, one end of the nut 16 cannot be rotated relative to the second stage wheel (final stage wheel) 5 by a connecting means other than the single round key 17, for example, a connecting means such as a spline. It may be connected so as to be separable in the direction.

  In the first and second aspects of the invention, the speed reduction mechanism is not limited to that of the present embodiment, and may be constituted by, for example, a worm gear or a bevel gear. The final stage wheel may be a worm wheel or a bevel gear.

Sectional drawing of the electrically driven linear actuator which is an Example of this invention. The side view of the ball screw unit shown in FIG. Sectional drawing of the state which removes a screw shaft case in the present Example shown in FIG. Sectional drawing of the state which removes a bracket in the present Example shown in FIG. Sectional drawing of the state which removes a ball screw unit in the present Example shown in FIG. Sectional drawing of the state which attaches a ball screw unit in the present Example shown in FIG. Sectional drawing of the state which attaches a bracket in the present Example shown in FIG. Sectional drawing of the state which attaches a screw shaft case in the present Example shown in FIG.

DESCRIPTION OF SYMBOLS 1 ... Gear case 1a ... Gear case main body 1b ... Cover 2 ... First stage pinion 3 ... First stage wheel 4 ... Second stage pinion 5 ... Second stage wheel (Final Corrugated wheel)
6 ... Tapered roller bearing 7 ... Oil seal 8 ... Electric motor 8a ... Motor shaft 9 ... Bracket 9a ... Flange 9b ... Inward flange portion 9c ... Female thread DESCRIPTION OF SYMBOLS 10 ... Bolt with a hexagon socket 11 ... Seal washer 12 ... Screw shaft case 12a ... Male screw 13 ... Lock nut 14 ... Ball screw 15 ... Screw shaft 15a ... Shaft Part 15b ... Stopper nut 16 ... Nut 17 ... Single round key 18 ... Taper roller bearing 19 ... Bearing presser 20 ... Ball screw unit 21 ... Single round key P ... Frame of the press drive mechanism of the electric press machine

Claims (2)

A gear case having a built-in speed reduction mechanism, an electric motor attached to the gear case, a bracket detachably attached to the gear case, and a screw shaft case detachably attached to the bracket by screwing and incorporating a ball screw. One end of a nut that constitutes the ball screw is connected to a final stage wheel that constitutes a speed reduction mechanism so as not to be relatively rotatable and separable in the axial direction, and the other end of the nut can receive a thrust load. A rolling bearing that is supported in the bracket by a bearing and that is opposite to the nut of the pair of rolling bearings that support the final-stage wheel is configured by a rolling bearing that can receive a thrust load. The rotation is converted into linear motion in the axial direction of the screw shaft constituting the ball screw and The electric linear actuator used in a state where the thrust load is loaded by,
A rolling bearing that supports the ball screw and the nut, and a bearing retainer that applies pressure to the rolling bearing with the amount of screw shaft case screwed into a final wheel and a bracket attached to the gear case. On the other hand, an electric linear actuator comprising a ball screw unit that is detachably incorporated when the ball screw is replaced.   By screwing the screw shaft case into the bracket, the end surface of the screw shaft case presses the side surface of the bearing retainer and preloads the rolling bearing through the bearing retainer, and the preload of the rolling bearing is screwed into the screw shaft case. The electric linear actuator according to claim 1, wherein the electric linear actuator is adjusted by an amount.

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