WO2021131524A1

WO2021131524A1 - Machine tool

Info

Publication number: WO2021131524A1
Application number: PCT/JP2020/044620
Authority: WO
Inventors: 大二郎吉川; 洋平浅羽
Original assignee: スター精密株式会社
Priority date: 2019-12-26
Filing date: 2020-12-01
Publication date: 2021-07-01
Also published as: JP2021104549A; TW202129173A

Abstract

There has been a need for effective measures against heat generated by a motor. This machine tool includes: a screw shaft; a motor that rotates the screw shaft; a ball screw nut that engages the screw shaft and moves along the screw shaft in accordance with the rotation of the screw shaft; a moving table that moves together with the ball screw nut; and an oil-air supply unit that supplies, to the ball screw nut, oil-air obtained by mixing a lubricant oil and air. The ball screw nut is attached to the moving table at a position more toward the motor side than the center of the moving table in the longitudinal direction of the screw shaft.

Description

Machine Tools

The present invention relates to a machine tool.

A configuration is disclosed in which an intermittent lubrication device for lubricating a nut portion of a lead screw and a compressed air supply source connected to a lubrication pipeline of the intermittent lubrication device are included, and lubrication and cooling are alternately performed (Patent Documents). 1).
Further, a configuration is disclosed in which compressed air mixed with lubricating oil is sent to a lubricated portion such as a gap between a nut and a ball screw of a machine tool feed system (see Patent Document 2).

Real Fairness 3-54832 Real Fairness 5-29805

In the configuration of a ball screw that linearly moves the nut by rotating the screw shaft, a motor for rotating the screw shaft is used. A motor is both a power source and a heat source. The heat generated by the motor causes thermal displacement of the screw shaft and other members. Therefore, it is necessary to take measures against the heat generated by the motor.

The present invention has been made in view of the above-mentioned problems, and provides an effective configuration for suppressing thermal displacement due to heat generation of a motor.

One aspect of the present invention is a machine tool, which engages with a screw shaft, a motor for rotating the screw shaft, and the screw shaft, and along the screw shaft in response to the rotation of the screw shaft. The ball screw nut includes a moving ball screw nut, a moving table that moves together with the ball screw nut, and an oil air supply unit that supplies oil air mixed with lubricating oil and air to the ball screw nut. It is attached to the moving table at a position closer to the motor than the center of the moving table in the longitudinal direction of the screw shaft.

According to the above configuration, the ball screw nut that receives the oil air supply is attached at a position close to the motor of the moving table. Therefore, by cooling the ball screw nut, the position close to the motor can be cooled, and the thermal displacement due to the heat generated by the motor can be suppressed.

The block diagram which shows the connection relation of each part of an NC lathe simply. The figure which shows a part structure of an NC lathe. The figure which shows the relationship between a moving table and a ball screw nut from the viewpoint of the direction parallel to the X axis. The figure which shows the structural example of NC lathe schematically.

Hereinafter, embodiments of the present invention will be described with reference to each figure. Each figure is merely an example for explaining the present embodiment. In addition, since each figure is an example, the shapes, ratios, etc. may not be consistent with each other, or some of the figures may be omitted, but such inconsistency or omission affects the explanation. Not reachable.

FIG. 1 simply shows the connection relationship of each part constituting the NC (Numerical Control) lathe 10 according to the present embodiment by a block diagram. The NC lathe 10 is a kind of machine tool. The NC lathe 10 has an NC device 11 as a computer. The NC device 11 is equipped with a machining program, and numerically controls the movement of each part necessary for machining, such as the spindle 20, the tool post 30, and the ball screw 40, according to the machining program.

The NC device 11 is connected to, for example, each part such as a spindle motor 21, an X-axis motor 31, a Y-axis motor 32, a ball screw motor 41, and an oil air supply part 50, and controls the drive of each part. The spindle motor 21 is a motor for rotating the spindle 20. The spindle 20 can rotate while gripping the rod-shaped work W, which is the object to be machined. The axis of the work W held by the spindle 20 and the spindle 20 is also referred to as a Z axis.

The X-axis motor 31 is a motor for moving the tool post 30 in the positive or negative direction of the X-axis, and the Y-axis motor 32 is for moving the tool post 30 in the positive or negative direction of the Y-axis. It is a motor. Both the X-axis and the Y-axis are perpendicular to the Z-axis, and the X-axis and the Y-axis are orthogonal to each other. The tool post 30 supports one or more blades for processing the work W. A knife is also called a tool.

The ball screw motor 41 is a motor for driving the ball screw 40. As shown in FIG. 2, the ball screw 40 includes a screw shaft 42 and a ball screw nut 43 that engages with the screw shaft 42. The oil / air supply unit 50 supplies oil air, which is a mixture of lubricating oil and air, to a predetermined location including the ball screw nut 43.

The above configuration is an example. For example, the NC lathe 10 may have a mechanism for moving the spindle 20 in the plus direction or the minus direction of the Y axis or the Z axis. In this case, a ball screw can be used to move the spindle 20. Further, the spindle 20 includes a collet that grips the work W so as to be openable. The spindle 20 may be either a front spindle or a back spindle that a lathe generally has. If the spindle 20 is the back spindle, the NC lathe 10 further has a front spindle (not shown). Further, the number of tool rests and the moving direction are not limited to the above examples. For example, the tool post may be moved in the positive or negative direction of the Z axis. A ball screw can be used for moving the tool post in each direction of the X-axis, Y-axis, or Z-axis, as in the spindle 20. The NC lathe 10 has each amplifier that supplies the necessary power to each motor.

FIG. 2 shows a partial configuration of an NC lathe 10 including a ball screw 40 and a moving table 60. In FIG. 2, each configuration except the oil / air supply unit 50 in the figure is shown from a viewpoint in a direction parallel to the Z axis. The oil / air supply unit 50 is illustrated to the extent that its configuration can be understood, and is not necessarily arranged at the position and orientation shown in FIG. 2 in relation to the X, Y, and Z axes.

As shown in FIG. 2, one end of the screw shaft 42 of the ball screw 40 is connected to the ball screw motor 41 via a coupling member 44. As a result, the screw shaft 42 rotates with the rotation of the ball screw motor 41. The other end of the screw shaft 42 is rotatably supported by the screw shaft support portion 45 that stands upright from the installation surface. The screw shaft 42 supported in this way is long in a direction parallel to the X-axis.

A ball screw nut 43 is engaged around the screw shaft 42. As is known, a ball (not shown) for reducing friction is interposed between the ball screw nut 43 and the screw shaft 42. As the screw shaft 42 rotates, the ball screw nut 43 linearly moves along the screw shaft 42.

The ball screw nut 43 is attached to the moving table 60. Specifically, a protruding portion 62 projecting in the negative direction of the Y axis is formed on the lower surface of the moving table 60 on the ball screw motor 41 side and facing the negative direction of the Y axis. A ball screw nut 43 is embedded in the protruding portion 62. In the example of FIG. 2, the ball screw nut 43 is attached to the projecting portion 62 with a part protruding from the surface 61 of the moving table 60 facing the ball screw motor 41 side toward the ball screw motor 41 side. In FIG. 2, a portion of the ball screw nut 43 embedded in the moving table 60 is shown by a broken line.

Such a protruding portion 62 corresponds to an end portion of the moving table 60 on the ball screw motor 41 side in the longitudinal direction of the screw shaft 42. However, the ball screw nut 43 may be attached to the moving table 60 at a position closer to the ball screw motor 41 side than the center of the moving table 60 in the longitudinal direction of the screw shaft 42. Therefore, the ball screw nut 43 may be attached at a position farther from the ball screw motor 41 than the position shown in FIG. 2 so as not to exceed the center of the moving table 60.
In the example of FIG. 2, the moving table 60 is equipped with a spindle 20. Therefore, the moving table 60 and the spindle 20 move together with the ball screw nut 43 in the plus direction and the minus direction of the X axis.

The oil / air supply unit 50 includes a lubricating oil supply source 52 for supplying the lubricating oil 51, an air supply source 53 for supplying compressed air, and piping. The pipes include a first pipe 54 extending from the lubricating oil supply source 52, a second pipe 55 extending from the air supply source 53, a connector 56 to which the first pipe 54 and the second pipe 55 are connected, and a connector 56. It has a third pipe 57 that connects to the ball screw nut 43.

By mixing the lubricating oil 51 supplied from the lubricating oil supply source 52 through the first pipe 54 and the compressed air supplied from the air supply source 53 through the second pipe 55 in the connector 56. Oil air is generated. Oil air is supplied to the ball screw nut 43 through the third pipe 57.

The end of the third pipe 57 on the opposite side to the connector 56 is connected to the portion of the ball screw nut 43 protruding from the surface 61 toward the ball screw motor 41. The work of connecting the third pipe 57 to the portion of the ball screw nut 43 protruding from the surface 61 toward the ball screw motor 41 is easy. Since the ball screw nut 43 is movable, the third pipe 57 has a length and flexibility so that it can move following the movement of the ball screw nut 43. The connector 56 has a check valve for preventing the lubricating oil 51 and the compressed air from flowing back into the first pipe 54 and the second pipe 55.

The oil air supplied to the ball screw nut 43 penetrates between the ball screw nut 43 and the screw shaft 42 to form an oil film on the ball surface. As a result, the frictional resistance between the ball screw nut 43 and the screw shaft 42 is reduced, and the ball screw nut 43 is smoothly moved. Further, the oil air containing air cools the ball screw nut 43, the screw shaft 42, and the peripheral portion.

FIG. 3 shows the relationship between the moving table 60 on which the spindle 20 is mounted and the ball screw nut 43 from the viewpoint of the direction parallel to the X axis. According to FIG. 3, the protruding portion 62 is formed at the center or substantially the center of the moving table 60 in the Z-axis direction. A screw shaft 42 is inserted inside the ball screw nut 43. Although not shown, the posture of the moving table 60 may be regulated by a guide member such as a guide rail extending in parallel with the screw shaft 42 so that the moving table 60 can move stably along the screw shaft 42. ..

The NC device 11 drives the lubricating oil supply source 52 and the air supply source 53 during the machining period from the start to the end of machining of the work W according to the machining program, and continuously oils air to the ball screw nut 43. Supply. The lubricating oil supply source 52 is a metering pump, which supplies a metering amount of lubricating oil per hour during operation. The oil / air supply unit 50 may supply oil / air to a portion requiring lubrication or cooling other than the ball screw nut 43 by another pipe (not shown). The NC device 11 is configured to supply oil air from the oil air supply unit 50 during the machining period, so that the oil air supply is stopped outside the machining period. Heat is likely to be generated by driving the motor during the machining period of the work W, but if oil air is supplied while the work W is not being machined (during the machining is stopped), the ball screw nut 43 continues to be cooled. Therefore, thermal deformation may occur due to cooling. By stopping the oil / air supply while the processing is stopped, it is possible to prevent the ball screw 40 from being cooled more than necessary and to suppress the occurrence of thermal deformation.

There are various modes of machining the work W according to the machining program. As one of such machining, in the present embodiment, the ball screw nut 43 is vibrated along the screw shaft 42 to machine the work W. Assuming an aspect. That is, the NC device 11 repeatedly switches the rotation direction of the screw shaft 42 in a short cycle by controlling the rotation of the ball screw motor 41, and the ball screw nut 43 has a fine reciprocating motion, that is, along the screw shaft 42. Make it vibrate. The NC device 11 realizes a predetermined machining by combining such vibration, the action of the tool of the tool post 30 on the work W, and the rotation of the spindle 20.

When the ball screw nut 43 is subjected to a fine reciprocating operation, the oil film is likely to run out on the ball surface, which tends to increase the frictional resistance and cause wear of metal members such as the ball, the screw shaft 42, and the ball screw nut 43. However, in the present embodiment, oil air is continuously supplied to the ball screw nut 43 by the oil air supply unit 50 during the processing period according to the processing program. As a result, it is possible to avoid an increase in frictional resistance and wear of the member as described above in the processing involving the fine reciprocating operation of the ball screw nut 43. Further, when the ball screw nut 43 is made to make a minute reciprocating motion, the motor repeatedly switches the rotation direction in a short cycle, so that the load applied to the motor becomes larger than that in normal machining. As a result, heat is likely to be generated in the motor. However, in the present embodiment, oil air is continuously supplied to the ball screw nut 43 by the oil air supply unit 50 during the processing period according to the processing program. This makes it possible to more effectively cool the heat generated from the motor in the machining involving the fine reciprocating operation of the ball screw nut 43.

The structure mounted on the moving table 60 is not limited to the spindle 20. For example, the tool post 30 may be mounted on the moving table 60. That is, this embodiment can also be applied to the case where the work W is machined by linearly moving the tool post 30 by the unit of the motor, the ball screw 40 and the moving table 60. In particular, when the ball screw nut of the tool post 30 is used for a fine reciprocating motion, it is possible to realize vibration cutting that makes it easy to divide chips by creating a time during which the tool does not come into contact with the work W during machining of the work W. By supplying oil air to the ball screw of the tool post 30, it is possible to effectively cool the heat of the motor generated by the load of vibration cutting. Of course, the machine tool may have a plurality of units of a motor, a ball screw and a moving table.

The machine tool assumed by this embodiment is not limited to the NC lathe. The present embodiment can be applied as long as the desired structure is linearly moved by using a motor, a ball screw, and a unit of a moving table.

As described above, according to the present embodiment, the machine tool engages with the screw shaft 42, the motor for rotating the screw shaft 42 (for example, the ball screw motor 41), and the screw shaft 42 to rotate the screw shaft 42. A ball screw nut 43 that moves along the screw shaft 42 accordingly, a moving table 60 that moves together with the ball screw nut 43, and an oil air supply unit 50 that supplies oil air mixed with lubricating oil and air to the ball screw nut 43. , Equipped with. The ball screw nut 43 is attached to the moving table 60 at a position closer to the motor than the center of the moving table 60 in the longitudinal direction of the screw shaft 42.
According to the above configuration, the ball screw nut 43 is attached to the moving table 60 at a position close to the motor as a heat source. Therefore, by cooling the ball screw nut 43 with oil air, the position close to the motor can be cooled, and the thermal displacement due to the heat generated by the motor can be suppressed. Thermal displacement is also called thermal deformation.

Further, according to the present embodiment, the ball screw nut 43 may be attached to the end portion of the moving table 60 on the motor side in the longitudinal direction of the screw shaft 42.
According to the above configuration, by providing the ball screw nut 43 at the position closest to the motor on the moving table 60, the cooling effect on the heat generated by the motor can be further enhanced.

Further, according to the present embodiment, the moving table 60 is equipped with a spindle 20 that grips and rotates the work W. Alternatively, the moving table 60 is equipped with a tool post 30 that supports a tool for processing the work W. Then, the machine tool may process the work W by vibrating the ball screw nut 43 along the screw shaft 42 by switching the rotation direction of the screw shaft 42.
According to the above configuration, each event such as frictional resistance between members, wear of members, and heat generation of a motor, which tends to increase in processing accompanied by vibration, can be accurately suppressed by the effects of lubrication and cooling by oil air.

The direction in which the screw shaft 42 faces is the horizontal direction in the example of FIG. Since the lubricating oil stagnates in the direction of gravity, when the screw shaft 42 faces in the horizontal direction, the oil film is likely to run out around the screw shaft 42, particularly in the antigravity direction. However, in the present embodiment, the oil air is supplied to the ball screw nut 43 by the oil air supply unit 50. As a result, even if the screw shaft 42 is oriented in the horizontal direction, it is possible to avoid an increase in frictional resistance and wear of the member due to running out of the oil film or the like.
However, this embodiment can be applied to a configuration in which the direction of the screw shaft 42 is not horizontal.

FIG. 4 is a diagram schematically illustrating the configuration of the NC lathe 10 in which the spindle 20 (particularly the front spindle 20A) moves. The NC lathe 10 shown in FIG. 4 has a front spindle 20A for gripping the work W, a guide bush 70, and a main tool post 30A and a front spindle 20A provided with a tool T for machining the work W gripped by the front spindle 20A. It has a back spindle 20B to which the work is delivered, a back tool post 30B for processing the work W gripped by the back spindle 20B, and the like. The front main shaft 20A and the back main shaft 20B are collectively referred to as the main shaft 20, and the main turret 30A and the back turret 30B are collectively referred to as the turret 30.

In FIG. 4, the front spindle 20A is movable in the Z-axis direction, and the main tool post 30A is movable in the X-axis direction and the Y-axis direction. The work W gripped by the front spindle 20 is supported by the guide bush 70 and machined by the tool T attached to the main tool post 30A.

The rear spindle 20B can move not only in the Z-axis direction but also in the X-axis direction. When the work W gripped by the front spindle 20A is finished to be machined by the tool T of the main tool post 30A, the back spindle 20B is set so that the spindle center line of the front spindle 20A and the spindle center line of the rear spindle 20B are on the same line. It moves in the X-axis and Z-axis directions and receives the work W from the front spindle 20A. The back spindle 20B that receives the work W from the front spindle 20A moves in the Z-axis direction and the X-axis direction, and the work W gripped by the back spindle 20B is processed by the tool T attached to the back tool post 30B. When the processing is completed, the back spindle 20B moves in the Z-axis direction and the X-axis direction in order to move to a predetermined processed work discharge position.

When comparing the front spindle 20A and the rear spindle 20B, the rear spindle 20B needs to move to the position of the tool T attached to the back tool post 30B, and the machined work W needs to be moved to a predetermined discharge position. Since it is necessary to transport to, the moving distance in the horizontal direction (particularly in the X-axis direction) becomes long. Since the moving distance becomes long, it is also necessary to lengthen the ball screw for moving the rear spindle 20B. However, when the ball screw becomes long, it is easily affected by thermal deformation such as expansion and contraction, so that the correction in consideration of thermal deformation becomes more complicated in order to move the back spindle 20B to a predetermined position with high accuracy. On the other hand, by supplying oil air to the ball screw for moving the rear spindle 20B in the horizontal direction (X-axis direction), the direction of the screw shaft is horizontal and the moving distance is longer than that of other shafts. Even a ball screw in the horizontal direction (X-axis direction) can be appropriately cooled.

10 ... NC lathe, 11 ... NC device, 20 ... spindle, 20A ... front spindle,
20B ... Back spindle, 21 ... Spindle motor, 30 ... Tool post,
30A ... main turret, 30B ... back turret, 40 ... ball screw,
41 ... ball screw motor, 42 ... screw shaft, 43 ... ball screw nut,
50 ... oil air supply part, 60 ... moving table, 62 ... protruding part,
70 ... Guide bush, T ... Tool, W ... Work

Claims

Screw shaft and
A motor that rotates the screw shaft and
A ball screw nut that engages with the screw shaft and moves along the screw shaft in response to rotation of the screw shaft.
A moving table that moves with the ball screw nut,
It is provided with an oil air supply unit that supplies oil air, which is a mixture of lubricating oil and air, to the ball screw nut.
A machine tool characterized in that the ball screw nut is attached to the moving table at a position closer to the motor than the center of the moving table in the longitudinal direction of the screw shaft.
The machine tool according to claim 1, wherein the ball screw nut is attached to the end of the moving table on the motor side in the longitudinal direction of the screw shaft.
The moving table is equipped with a spindle that grips and rotates the work, or a tool post that supports a tool for processing the work.
The machine tool according to claim 1 or 2, wherein the ball screw nut is vibrated along the screw shaft by switching the rotation direction of the screw shaft to process the work.
The machine tool according to any one of claims 1 to 3, wherein the screw shaft faces in the horizontal direction.