JPH0473450A - Ball screw unit and extension contraction device utilizing ball screw unit - Google Patents

Abstract

PURPOSE:To obtain an extension contraction device with high precision which operates at a high speed and has a lightweight and compact structure by constituting a ball screw nut from the first ball screw nut which is engaged with a spline nut for transmitting a torque to a screw shaft and a fixed part and advances in the axial direction by the turn of the screw shaft and the second ball screw nut which shifts in the reverse direction. CONSTITUTION:An outer race 28 assembled on a spline nut 2 and the first ball screw nut 3 are fixed on a fixed part B, and the second ball screw nut 4 is fixed on a transfer body 5 which is moved in reciprocation, and the revolution movement of a motor, etc. is transmitted to a nut body 24 through a pulley 6 installed on the nut body 24 of the spline nut 2. Accordingly, when the revolution movement of the motor is transmitted to a screw shaft 1 by the spline nut 2, the rectilinear movement in the axial direction by the first ball screw nut 3 is applied on the screw shaft 1, and the rectilinear movement along the screw shaft 1 is generated on the second ball screw nut 4. Accordingly, the sum of the stroke speed of the screw shaft 1 and the stroke speed of the second ball screw nut 4 becomes the transfer speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ball screw unit used, for example, in an arm for an industrial robot, and a telescopic device using the ball screw unit.

[Prior Art] A telescoping device that relatively moves a plurality of superimposed sliders using the power of a motor or the like and adjusts the length of a movable body constituted by these sliders is used for slide covers of mechanical devices and various other devices. Used for doors of structures, arms of industrial robots, etc.

Conventionally, in such telescoping devices, the mechanism for converting the rotary motion of the motor into linear motion and sliding the sliders relative to each other has been, for example, a mechanism in which a rack fixed to the slider is linearly driven by a pinion connected to a motor or the like. Common methods include a method in which a pulley fixed to a slider is pulled by winding a wire, and the like.

[Problems to be Solved by the Invention] By the way, as an example of how the telescoping device is used in an industrial robot, there is a method as shown in FIG. 8, for example. Specifically, it is used as a telescoping arm C that supports a tool part that performs a predetermined process on a workpiece a on the robot body e, and the tool part is placed in a standby position (solid line in Figure 8). As a means of reciprocating between the tool and the machining position (solid line in Figure 8), the tool repeatedly approaches the workpiece a that is continuously sent at regular intervals on the production line d. It is used.

A telescoping device used as a telescoping arm in this manner is required to meet the following performance requirements.

First, the goal is to achieve highly accurate telescoping motion.

As mentioned above, the telescoping device has the role of sending the tool part in the standby position to the correct machining position, so if there is an error in the amount of extension or contraction, the error will accumulate due to repeated movements, and the tool part will not be able to move to the correct position. This is because it is only possible to send it to the processing position.

The second point is to increase the speed of the telescoping motion. This is because in industrial robots, the speed at which the tool section is sent from the standby position to the processing position and the speed at which it is removed from the processing position to the standby position are closely linked to the speed of the production line, that is, the production efficiency.

Furthermore, the third point is to make the structure more compact and lightweight.

In recent years, industrial robots are required to have increasingly complex movements and multifunctionality, and it has become necessary to mount various devices around the robot body or tool section. Therefore,
In designing a lightweight and compact robot, the telescoping device must also be compact and lightweight.

However, in the conventional telescoping device described above, movement errors tend to occur in each slider when the telescoping motion is stopped or reversed, so the precision of the telescoping motion during repeated motions is poor.
In addition, there is a problem in that rattling is likely to occur at moderate high speeds.

In addition, in actual manufacture, the structure becomes complicated, and the conventional telescopic device cannot sufficiently meet the demands for lighter weight and more compact robot arms.

The present invention was made in view of these problems, and its purpose is to provide a ball screw unit that enables the design of a highly accurate, high-speed, lightweight and compact telescoping device. .

Another object of the present invention is to provide a highly accurate, high-speed, lightweight, and compact telescoping device using the above ball screw unit.

[Means for Solving the Problems] In order to achieve the above object, the ball screw unit of the present invention has a first spiral ball rolling groove and a second spiral ball rolling groove that have a reverse thread relationship with each other. a screw shaft having a groove formed therein and a linear ball rolling groove formed along the axial direction to intersect with the first spiral ball rolling groove; and a screw shaft rotatably supported by the fixed part. A spline nut that works together with the linear ball rolling groove to sandwich the ball and transmits torque to the screw shaft, and a spline nut that is locked to the fixed part and works together with the first spiral ball rolling groove. The first ball screw nut, which pinches the ball and propels it in the axial direction as the screw shaft rotates, works together with the second spiral ball rolling groove to sandwich the ball, and A second ball screw nut that moves as the screw shaft rotates.

Further, in the telescopic device of the present invention, the first spiral ball rolling groove and the second spiral ball rolling groove are formed in a reverse thread relationship with each other, and the first spiral ball rolling groove is formed with the first spiral ball rolling groove. A screw shaft having a linear ball rolling groove formed along the axial direction so as to intersect with the groove, and a screw shaft rotatably supported by a fixed part and working together with the linear ball rolling groove to sandwich the ball,
A spline nut that transmits torque to the screw shaft, and a spline nut that is locked to the fixed part and works together with the first spiral ball rolling groove to sandwich the ball, and as the screw shaft rotates. a first ball screw nut that propels the ball in the axial direction; and a second ball screw nut that works with the second spiral ball rolling groove to sandwich the ball and moves as the screw shaft rotates. and a movable body formed of a plurality of mutually sliding sliders, the sliders at both ends being respectively connected to the fixed part and the second ball screw nut. It is.

In such technical means, the ball screw unit operates as follows. That is, when a prime mover such as a motor transmits torque to the spline nut to rotate the screw shaft, the screw shaft strokes in the axial direction due to the first ball screw nut locked to the fixed part, while the second ball screw rotates. The ball screw nut moves on the outer peripheral surface of the screw shaft in the same direction as the stroke direction of the screw shaft.

At this time, the first spiral ball rolling groove and the second spiral ball rolling groove of the screw shaft do not necessarily have to be formed with the same lead, and the spiral ball rolling groove of these spiral ball rolling grooves does not necessarily have to be formed with the same lead. The lengths of the formation regions may also be changed in design as appropriate. However, from the perspective of maximizing the stroke amount of the second ball screw nut relative to the fixed part, the time required for the first ball screw nut to move through the formation area of the first helical ball rolling groove and The lead of each rolling groove and the length of the forming area may be determined so that the time required for the second ball screw nut to move through the forming area of the second spiral ball rolling groove is equal. is necessary.

Further, the number of the linear ball rolling grooves may be changed as appropriate depending on the magnitude of the torque transmitted from the spline nut to the screw shaft.

Furthermore, the movable body in the above-mentioned expansion and contraction device may be one that can freely expand and contract as the second ball screw nut moves and can prevent the second ball screw nut from rotating together with the screw shaft. , the number and shape of sliders may be changed as appropriate.

For example, if the shape of the slider is made into a cylinder and a movable body is placed to cover the screw, it can be used as a robot arm with telescoping functions.If the slider is made into a plate shape, it can be used as an automatic opening/closing door for various structures. be able to.

[Work] The above technical means works as follows.

According to the ball screw unit of the present invention, while the screw shaft strokes with respect to the fixed part, the second ball screw nut strokes with respect to the screw shaft, so that the second ball screw nut can be fixed with a compact configuration. In addition to being able to set a large amount of movement for the part, the movement speed is also increased.

Furthermore, according to the telescoping device using the ball screw unit of the present invention, it has a light and compact structure, and can provide long stroke high-speed telescoping motion to the movable body.
Since the expansion and contraction motion is obtained by a rolling bearing using balls, it is possible to minimize movement errors and wobbling of the slider by applying preload to the balls.

[Example] Hereinafter, a ball screw unit of the present invention and a telescopic device using the same will be described in detail based on the accompanying drawings.

FIG. 1 shows a first embodiment of the ball screw unit of the present invention, which includes a screw shaft 1 in which a plurality of ball rolling grooves are formed, and a screw shaft rotatably supported by a fixed part 8. 1
a spline nut 2 that transmits torque to the screw shaft 1; a first ball screw nut 3 disposed on the fixed part 8 that strokes the screw shaft 1 in the axial direction; It is composed of a second ball screw nut 4 that strokes.

The screw shaft 1 has a first helical ball rolling groove 11 and a second helical ball rolling groove 12 which have opposite threads to each other.
are formed of the same lead, and the first ball screw nut 3 is screwed into the former, while the second ball screw nut 4 is screwed into the latter. Further, in a part of the screw shaft 1, a linear ball rolling groove 13 for guiding the spline nut 2 is connected to a first spiral ball rolling groove 11.
Three lines are formed so as to intersect with each other.

As shown in FIGS. 2 and 3, the spline nut 2 works together with the linear ball rolling groove 13 to rotate the ball 2.
1, a nut body 24 having a load ball groove 22 that sandwiches the nut, a non-load ball groove 23 that pairs with the load ball groove 22, and a circumferential guide groove that communicates both ends of these grooves; is inserted into the nut body 24,
A resin ball having a long hole 25 for holding and aligning the loaded balls 21a rolling in the loaded ball groove 22, and forming a circulation path for the unloaded balls 21b in conjunction with the unloaded ball groove 23 and the guide groove. It is composed of a retainer 26.

Further, an outer ring 28 of an angular contact bearing is provided on the outer peripheral surface of the nut main body 24 via a ball 27, so that the nut main body 24 can freely rotate with respect to the outer ring 28.

Therefore, by fixing the flange portion 29 formed on the outer ring 28 to the fixing portion 8 by means such as bolt connection, the screw shaft 1 passing through the nut body 24 can freely perform rotational movement, reciprocating movement, or a combination of these movements. It is possible to give.

On the other hand, as shown in FIGS. 4 and 5, the first ball screw nut 3 has a helical load ball groove 32 that sandwiches the ball 31 together with the first helical ball rolling groove 11. A nut body 35 has a rolling hole 33 for a non-load ball on the inner circumferential surface, and seven flange portions 34 for fixing are formed on the outer circumferential surface, and a nut body 35 has a nut body 35 on both axial end surfaces of the nut body 35. Fixed, spiral loaded ball groove 32 and said rolling hole 3
3, and an end cap 36 that communicates with 3.

It should be noted that the second ball screw nut 4 also has the same old nut body and end gap 42 as the first ball screw nut 3.
The helical load ball rolling groove 43 formed on the inner circumferential surface of the nut body 41 has a reverse thread to that of the first ball screw nut 3, and the second spiral of the screw shaft 1 The basic usage of the ball screw unit of this embodiment configured as above is as shown by the dashed line in FIG. It is. That is, while the outer ring 28 assembled to the spline nut 2 and the first ball screw nut 3 are fixed to the fixed part 8, the second ball screw nut 4 is fixed to the movable body 5 which is reciprocated, and the spline nut 2 The rotational motion of a motor or the like (not shown) is transmitted to the nut body 24 through a pulley 6 attached to the nut body 24.

According to this, when the rotational motion of the motor is transmitted to the screw shaft 1 by the spline nut 2, the screw shaft 1 is given linear motion in the axial direction by the first ball screw nut 3, while the second ball A linear motion along the screw shaft 1 occurs in the screw nut 4.

FIGS. 6 and 7 show a first embodiment of a telescoping device constructed using the above ball screw unit, and show the retracted and extended states, respectively.

The fixed part B includes three cylindrical sliders 71 with different diameters,
A movable body 7 is fixed so as to cover the screw shaft 1, and is connected to the slider 72 and 73 so as to be mutually slidable in the axial direction but not rotatable in the circumferential direction. The second ball screw nut 4 is fixed to one end of the slider.

Each slider 71, 72, 73 is connected by a pair of sliding bearings 74 arranged at intervals to prevent bending or distortion from occurring in the movable body 7 during extension or contraction.

Further, a stepping motor H is connected to a pulley 6 provided on the spline nut 2 via a timing belt 8.

In the above configuration, by applying a drive pulse to the Stellar pin motor H to rotate the screw shaft 1 by a predetermined angle, the output slider 73 fixed to the second ball screw nut 4 is moved to the -th and second ball screws. The movable body 7 can be freely expanded and contracted to any length by stroking according to the leads of the two spiral ball rolling grooves 11 and 12.

At this time, in the telescoping device of this embodiment, the accuracy of the ball screw unit described above can be used as is as the movement accuracy of the output slider 73, and the movement accuracy of the output slider 73 in repeated telescoping motions, that is, the expansion and contraction of the movable body 7. High accuracy can be expected.

Furthermore, since the sum of the stroke speed of the screw shaft 1 and the stroke speed of the second ball screw nut 4 becomes the moving speed of the output slider 73, the movable body 7 has the advantage of generating high-speed telescoping motion when the motor H rotates at a low speed. It also has

Furthermore, a highly accurate telescoping motion can be obtained with a simple structure in which the telescoping movable body 7 is disposed to cover the ball screw unit of the present invention, and the device can be easily made lighter and more compact. It is.

In addition, in this embodiment, the ball screw unit of the present invention was explained in relation to a telescopic device, but the use of the ball screw unit is not limited to this. It can also be used as a feeding device for equipment that requires reciprocating motion.

[Effects of the Invention] As explained above, according to the ball screw unit of the present invention, it is possible to set a large amount of movement and movement speed of the second ball screw nut relative to the fixed part with a compact device configuration. This makes it possible to easily design a lightweight, compact, and high-speed telescoping device.

Furthermore, according to the telescopic device using the ball screw unit of the present invention, the device can be made lighter and more compact, and the telescopic movement can be made faster.In addition, by applying preload to the balls, the slider can be moved with high accuracy and can be prevented from wobbling. This makes it possible to obtain telescopic movements with high repeatability.

[Brief explanation of drawings]

FIG. 1 is a front sectional view showing a first embodiment of the ball screw unit of the present invention, FIGS. 2 and 3 are front and side sectional views showing a spline nut according to the first embodiment, and FIGS. FIG. 5 is a front and side sectional view showing the first ball screw nut according to the first embodiment, FIG. 6 is a schematic diagram showing the telescopic device of the present invention in its shortened state, and FIG. 7 is the telescopic device of the present invention. FIG. 8 is a schematic diagram showing the state of the device when it is extended. FIG. 8 is a schematic diagram showing an example of an industrial robot using the telescoping device. [Description of symbols] 1: Screw shaft 2 Spline nut 3: First ball screw nut 4: Second ball screw nut 7: Movable body 11: First spiral ball rolling groove 12: Second spiral Ball rolling groove 13: Linear ball rolling groove 71, 72, 73 varnish slider B 2 fixing part

Claims (2)

[Claims] (1) A first helical ball rolling groove and a second helical ball rolling groove are formed with opposite threads to each other, and a shaft is formed so as to intersect with the first helical ball rolling groove. A screw shaft having a linear ball rolling groove formed along the direction is rotatably supported by a fixed part, and together with the linear ball rolling groove, the ball is sandwiched, and torque is applied to the screw shaft. a spline nut for transmitting the transmission; and a second spline nut that is locked to the fixed part and works with the first spiral ball rolling groove to sandwich the ball and propel it in the axial direction as the screw shaft rotates. The second ball screw nut is comprised of a first ball screw nut and a second ball screw nut that works with the second spiral ball rolling groove to sandwich the ball and moves as the screw shaft rotates. ball screw unit. (2) A first helical ball rolling groove and a second helical ball rolling groove are formed with opposite threads to each other, and a shaft is formed so as to intersect with the first helical ball rolling groove. A screw shaft with a linear ball rolling groove formed along the direction is rotatably supported by a fixed part, and works together with the linear ball rolling groove to sandwich the ball and transmit torque to the screw shaft. a spline nut that is locked to the fixed portion, and that works together with the first spiral ball rolling groove to sandwich the ball and propel it in the axial direction as the screw shaft rotates. a second ball screw nut that works with the second spiral ball rolling groove to sandwich the ball and moves as the screw shaft rotates;
1. A telescoping device that is telescopically formed from a plurality of sliders that slide relative to each other, and that the sliders at both ends are each comprised of a movable body connected to the fixed portion and a second ball screw nut.