TW202129173A - Machine tool - Google Patents

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 tool

The invention relates to a machine tool.

A structure is disclosed that includes an intermittent oil supply device for lubricating the nut portion of the feed screw, and a compressed air supply source connected to the oil supply line of the intermittent oil supply device to alternately perform lubrication and cooling (see Patent Document 1). Furthermore, there is disclosed a structure that supplies compressed air mixed with lubricating oil to lubrication parts such as the gap between the nut and the ball screw of the machine tool feed system (refer to Patent Document 2). [Prior technical literature] [Patent literature]

[Patent Document 1] Japanese Patent No. 3-54832 [Patent Document 2] Japanese Patent No. 5-29805

[The problem to be solved by the invention]

In the structure of the ball screw that linearly moves the nut by the rotation of the screw shaft, a motor for rotating the screw shaft is used. The motor is the power source and at the same time is the heat source. The heat of the motor becomes the cause of thermal displacement of the screw shaft or other components. Therefore, it is necessary to take countermeasures against the heat radiated by the motor.

The present invention is completed in view of the above-mentioned problems, and provides a structure that effectively suppresses the thermal displacement caused by the heating of the motor. [Technical means to solve the problem]

One aspect of the present invention is a machine tool comprising: a screw shaft; a motor that rotates the screw shaft; a ball screw nut engaged with the screw shaft and moves along the screw shaft in response to the rotation of the screw shaft The screw shaft moves; a moving table, which moves together with the ball screw nut; and an oil and gas supply part, which supplies oil and gas mixed with lubricating oil and air to the ball screw nut; and the ball screw nut is on the screw The shaft is mounted on the moving table at a position closer to the motor side than the center of the moving table in the longitudinal direction.

According to the above structure, the ball screw nut that receives the oil and gas supply is installed on the moving platform near the motor. Therefore, by cooling the ball screw nut, the position close to the motor can be cooled, thereby suppressing the thermal displacement caused by the heating of the motor.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Each figure is only an illustration for explaining this embodiment. In addition, since each figure is only an illustration, there may be cases where the shapes and ratios do not match each other, or part of the illustration is omitted, but such mismatch and omission do not affect the description.

FIG. 1 is a block diagram schematically showing the connection relationship of the various parts of the NC (Numerical Control) lathe 10 of this embodiment. NC lathe 10 is a 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 according to the machining program, the movements of the main shaft 20, the tool holder 30, the ball screw 40 and other parts required for machining are numerically controlled.

The NC device 11 is connected to various parts 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, for example, and controls the driving of these parts. The spindle motor 21 is a motor for rotating the spindle 20. The spindle 20 can rotate while holding a rod-shaped workpiece W as an object to be processed. The spindle 20 and the axis of the workpiece W held by the spindle 20 are also referred to as the Z axis.

The X-axis motor 31 is a motor for moving the tool holder 30 in the positive or negative direction of the X-axis, and the Y-axis motor 32 is a motor for moving the tool holder 30 in the positive or negative direction of the Y-axis. Both the X axis and the Y axis are perpendicular to the Z axis, and the X axis and the Y axis are orthogonal. The tool holder 30 supports more than one tool for processing the workpiece W. The cutter 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 engaged with the screw shaft 42. The oil and gas supply unit 50 supplies oil and gas mixed with lubricating oil and air to specific parts including the ball screw nut 43.

The above configuration is only an example. For example, the NC lathe 10 may also have a mechanism for moving the main shaft 20 in the positive or negative direction of the Y axis or the Z axis. In this case, a ball screw can be used for the movement of the main shaft 20. In addition, the spindle 20 is provided with a chuck for releasably holding the workpiece W. The spindle 20 can be either a front spindle or a back spindle that a lathe generally has. If the spindle 20 is a back spindle, the NC lathe 10 further has a front spindle (not shown). In addition, the number and moving direction of the tool holders are not limited to the above examples. For example, the tool holder can also be moved in the positive or negative direction of the Z axis. For the movement of the tool holder in each direction of the X-axis, Y-axis, or Z-axis, as with the spindle 20, a ball screw can be used. The NC lathe 10 has amplifiers for supplying required electric power to the motors.

FIG. 2 shows the partial structure of the NC lathe 10 including the ball screw 40 and the moving table 60. As shown in FIG. In Fig. 2, the various components in the figure except for the oil and gas supply part 50 are shown from a viewpoint in a direction parallel to the Z axis. The oil and gas supply part 50 is illustrated to a degree sufficient to understand its structure, and in relation to the X, Y, and Z axes, it is not necessarily arranged in the position and direction shown in FIG. 2.

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. Thereby, the screw shaft 42 rotates with the rotation of the ball screw motor 41. The other end of the screw shaft 42 is supported in a rotatable state by a screw shaft support part 45 erected from the installation surface. The screw shaft 42 thus supported is elongated in the direction parallel to the X-axis.

A ball screw nut 43 is engaged around the screw shaft 42. It is known that a ball (not shown) is interposed between the ball screw nut 43 and the screw shaft 42 to reduce friction. By the rotation of the screw shaft 42, the ball screw nut 43 moves linearly along the screw shaft 42.

The ball screw nut 43 is installed on the moving table 60. Specifically, a protrusion 62 protruding in the negative direction of the Y-axis is formed at the end of the moving table 60 on the side of the ball screw motor 41 and facing the negative direction of the Y-axis. Furthermore, the ball screw nut 43 is embedded in the protrusion 62. In the example of FIG. 2, the ball screw nut 43 is attached to the protruding portion 62 in a state where a part of the ball screw nut 43 emerges from the surface 61 of the moving table 60 facing the ball screw motor 41 side to the ball screw motor 41 side. In FIG. 2, the part of the ball screw nut 43 embedded in the moving table 60 is indicated by a dotted line.

Such a protrusion 62 corresponds to the end 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 in the moving table 60 only needs to be installed at a position closer to the ball screw motor 41 than the center of the moving table 60 in the longitudinal direction of the screw shaft 42. Therefore, the ball screw nut 43 can also be installed at a position farther from the ball screw motor 41 than the position shown in FIG. 2 by no more than the center of the moving table 60. In the example of FIG. 2, the mobile station 6 is equipped with a spindle 20. Therefore, the moving table 60 and the main shaft 20 move together with the ball screw nut 43 in the positive or negative direction of the X axis.

The oil and gas supply unit 50 includes a lubricating oil supply source 52 that supplies lubricating oil 51, an air supply source 53 that supplies compressed air, and piping. The piping has a first piping 54 extending from the lubricating oil supply source 52, a second piping 55 extending from the air supply source 53, a connector 56 for connecting the first piping 54 and the second piping 55, and a connector 56 The third pipe 57 connected to the ball screw nut 43.

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 are mixed in the connector 56 to generate oil gas. The oil and gas are 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 part of the ball screw nut 43 that protrudes from the surface 61 to the ball screw motor 41 side. The operation of connecting the third pipe 57 to the part of the ball screw nut 43 that protrudes from the surface 61 to the ball screw motor 41 side is easy. Since the ball screw nut 43 can move, the third pipe 57 has a length and flexibility that 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 compressed air from flowing back into the first pipe 54 and the second pipe 55.

The oil and gas 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 surface of the ball. Thereby, the frictional resistance between the ball screw nut 43 and the screw shaft 42 is reduced, so that the ball screw nut 43 can move smoothly. In addition, the oil and gas containing air cools the ball screw nut 43, the screw shaft 42, and the peripheral parts.

FIG. 3 shows the relationship between the moving table 60 on which the spindle 20 is mounted and the ball screw nut 43 from a viewpoint in a direction parallel to the X axis. According to FIG. 3, the protrusion 62 is formed in the center or substantially the center of the moving table 60 in the Z-axis direction. The screw shaft 42 is inserted through the inner side of the ball screw nut 43. Although not shown in the figure, the moving table 60 may be regulated by a guide member such as a guide rail extending parallel to the screw shaft 42 so that it 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 to continuously supply oil and gas to the ball screw nut 43 during the period from the start of the processing of the workpiece W to the end of the processing of the workpiece W according to the processing program. The lubricating oil supply source 52 is a quantitative pump, which supplies a fixed amount of lubricating oil every hour during the driving process. The oil and gas supply part 50 can also supply oil and gas to parts that need to be lubricated or cooled in addition to the ball screw nut 43 through other piping not shown. Furthermore, the NC device 11 is configured to supply oil and gas from the oil and gas supply part 50 during processing, so that the supply of oil and gas is stopped during the non-processing period. Although the drive motor is prone to generate heat during the processing of the workpiece W, if gas is supplied during the period when the workpiece W is not being processed (while the processing is stopped), the ball screw nut 43 will continue to be cooled, and heat may be generated due to cooling. Deformed. By stopping the supply of oil and gas during the processing stop, the ball screw 40 can be prevented from being cooled more than necessary, so that the occurrence of thermal deformation can be suppressed.

There are various aspects of processing the workpiece W according to the processing program. As one of such processing, in this embodiment, the following aspect is assumed: the ball screw nut 43 is vibrated along the screw shaft 42 and the workpiece W is processed. That is, the NC device 11 controls the rotation of the ball screw motor 41 to repeatedly switch the rotation direction of the screw shaft 42 in a short cycle, so that the ball screw nut 43 performs fine reciprocating motion, that is, vibrates along the screw shaft 42 . The NC device 11 realizes specific processing by combining such vibration, the action of the tool of the tool holder 30 on the workpiece W, and the rotation of the spindle 20.

When the ball screw nut 43 performs fine reciprocating motions, the oil film on the surface of the ball is prone to breakage, which may increase the frictional resistance, or the metal components such as the ball, the screw shaft 42, and the ball screw nut 43 may be worn away. However, in this embodiment, the oil and gas are continuously supplied to the ball screw nut 43 by the oil and gas supply part 50 during the processing in accordance with the processing program. As a result, in the processing accompanied by the fine reciprocating motion of the ball screw nut 43, the increase in frictional resistance and the abrasion of the components as described above can be avoided. In addition, when the ball screw nut 43 performs a minute reciprocating motion, the motor repeatedly switches the direction of rotation in a short cycle, and therefore, the load on the motor becomes larger than that of normal processing. As a result, heat is easily generated in the motor. However, in this embodiment, the oil and gas are continuously supplied to the ball screw nut 43 by the oil and gas supply part 50 during the processing in accordance with the processing program. As a result, the heat generated from the motor can be cooled more effectively in the processing accompanied by the fine reciprocating motion of the ball screw nut 43.

The structure mounted on the moving table 60 is not limited to the main shaft 20. For example, the tool holder 30 may be mounted on the moving table 60. That is, the present embodiment can also be applied to a case where the tool holder 30 is linearly moved by the unit of the motor, the ball screw 40, and the moving table 60 to process the workpiece W. In particular, when the ball screw nut of the tool holder 30 performs fine reciprocating motions, it is possible to create a time during the processing of the workpiece W that does not make the tool contact the workpiece W, and realizes the easy separation of cutting chips The vibration cutting. By supplying oil and gas to the ball screw of the tool holder 30, the heat of the motor generated by the load of vibration cutting can be effectively cooled. Of course, the machine tool can also have multiple units of motor, ball screw and moving table.

The machine tool assumed in this embodiment is not limited to the NC lathe. This embodiment can be applied as long as it is a configuration that uses a unit of a motor, a ball screw, and a moving table to linearly move a desired structure.

Thus, according to this embodiment, the machine tool includes: a screw shaft 42; a motor (for example, a ball screw motor 41) that rotates the screw shaft 42; and a ball screw nut 43 that is engaged with the screw shaft 42 and corresponds to the screw shaft 42 rotates and moves along the screw shaft 42; the moving table 60 moves together with the ball screw nut 43; and the oil and gas supply part 50, which supplies the ball screw nut 43 with oil and air mixed with oil. In addition, the ball screw nut 43 is installed on the moving table 60 at a position closer to the motor side than the center of the moving table 60 in the longitudinal direction of the screw shaft 42. According to the above structure, the ball screw nut 43 is installed on the moving table 60 near the motor as the heat source. Therefore, the oil and gas cooling the ball screw nut 43 can cool the position close to the motor, thereby suppressing the thermal displacement caused by the heating of the motor. Thermal displacement is also called thermal deformation.

Furthermore, according to this embodiment, the ball screw nut 43 can also be installed at the end of the moving table 60 on the motor side in the longitudinal direction of the screw shaft 42. According to the above configuration, by arranging the ball screw nut 43 at the position closest to the motor of the moving table 60, the cooling effect of the heat radiated by the motor can be further improved.

In addition, according to the present embodiment, the moving table 60 is equipped with a spindle 20 that grips and rotates the workpiece W. Or, the moving table 60 is equipped with a tool holder 30 supporting a tool for processing the workpiece W. Moreover, the machine tool can also process the workpiece W by switching the rotation direction of the screw shaft 42 to cause the ball screw nut 43 to vibrate along the screw shaft 42. According to the above configuration, the effects of oil and gas lubrication and cooling can reliably suppress the frictional resistance between the components, the wear of the components, and the heat generation of the motor that are likely to increase in the processing accompanied by the above-mentioned vibration.

The direction in which the screw shaft 42 faces is the horizontal direction in the example of FIG. 2. Since the lubricating oil will stagnate in the direction of gravity, when the screw shaft 42 is facing the horizontal direction, the oil film around the screw shaft 42 is likely to break, especially in the anti-gravity direction. However, in this embodiment, the oil and gas supply part 50 supplies oil and gas to the ball screw nut 43. Thereby, even if the screw shaft 42 is oriented in the horizontal direction, it is possible to avoid an increase in frictional resistance or abrasion of components due to breakage of the oil film or the like. However, this embodiment can also be applied to a configuration where the direction of the screw shaft 42 is not horizontal.

FIG. 4 is a diagram schematically illustrating the structure of the NC lathe 10 in which the spindle 20 (especially the front spindle 20A) moves. The NC lathe 10 shown in FIG. 4 has: a front spindle 20A, which holds a workpiece W; a bushing 70; a main tool holder 30A, which has a tool T for processing the workpiece W held by the front spindle 20A; The spindle 20B receives the workpiece from the front spindle 20A; the back side tool holder 30B is used to process the workpiece W held by the back spindle 20B; and so on. The front spindle 20A and the back spindle 20B are collectively referred to as the spindle 20, and the main tool holder 30A and the back tool holder 30B are collectively referred to as the tool holder 30.

In FIG. 4, the front spindle 20A can move in the Z-axis direction, and the main tool holder 30A can move in the X-axis direction and the Y-axis direction. The workpiece W held by the front spindle 20 is supported by the bushing 70 on one side, and processed by the tool T mounted on the main tool holder 30A on the other side.

The back spindle 20B can move in the X-axis direction in addition to the Z-axis direction. When using the tool T of the main tool holder 30A to finish processing the workpiece W held by the front spindle 20A, the back spindle 20B is such that the spindle center line of the front spindle 20A and the spindle center line of the back spindle 20B are on the same line. It moves along the X-axis and Z-axis directions, and the workpiece W is picked up from the front spindle 20A. The back spindle 20B that receives the workpiece W from the front spindle 20A moves in the Z-axis direction and the X-axis direction, and the workpiece W held by the back spindle 20B is processed by the tool T mounted on the back tool holder 30B. After the processing is completed, the back spindle 20B moves along the Z-axis direction and the X-axis direction to move to a specific processed workpiece discharge position.

Comparing the front spindle 20A with the back spindle 20B, it is found that the back spindle 20B needs to be moved to the position of the tool T installed on the back tool holder 30B, and the processed workpiece W needs to be transported to a specific discharge position. The moving distance in the horizontal direction (especially the X-axis direction) becomes longer. As the moving distance becomes longer, the ball screw used to move the back spindle 20B also needs to be extended. However, if the ball screw becomes longer, it is susceptible to thermal deformation such as expansion or contraction. Therefore, in order to move the back spindle 20B to a specific position with high accuracy, the correction in consideration of thermal deformation becomes more complicated. In contrast, by supplying oil and gas to the ball screw used to move the back spindle 20B in the horizontal direction (X-axis direction), even if the direction of the screw axis is horizontal and the moving distance is longer than other axes. The ball screw in the direction (X-axis direction) can also be properly cooled.

10: NC lathe 11: NC device 20: Spindle 20A: Front spindle 20B: Back spindle 21: Spindle motor 30: Tool holder 30A: Main tool holder 30B: Back side tool holder 31: X axis motor 32: Y axis motor 40: Ball screw 41: Ball screw motor 42: screw shaft 43: Ball screw nut 44: Joint structure 45: Screw shaft support part 50: Oil and Gas Supply Department 51: Lubricant 52: Lubricating oil supply source 53: Air supply source 54: The first piping 55: 2nd piping 56: Connector 57: 3rd piping 60: mobile station 61: The surface of the mobile station 62: protrusion 70: Bush T: Tools W: Workpiece

Figure 1 is a block diagram schematically showing the connection relationship between the various parts of the NC lathe. Figure 2 is a diagram showing part of the NC lathe. Figure 3 is a diagram showing the relationship between the moving table and the ball screw nut from the viewpoint of the direction parallel to the X axis. Figure 4 is a diagram schematically showing an example of the configuration of an NC lathe.

20: Spindle

40: Ball screw

41: Ball screw motor

42: screw shaft

43: Ball screw nut

44: Joint structure

45: Screw shaft support part

50: Oil and Gas Supply Department

51: Lubricant

52: Lubricating oil supply source

53: Air supply source

54: The first piping

55: 2nd piping

56: Connector

57: 3rd piping

60: mobile station

61: The surface of the mobile station

62: protrusion

W: Workpiece

Claims (4)

A machine tool is characterized by: a screw shaft; a motor that rotates the screw shaft; a ball screw nut, which is engaged with the screw shaft, and moves along the screw shaft corresponding to the rotation of the screw shaft; The moving table, which moves together with the ball screw nut; and the oil and gas supply part, which supplies oil and gas mixed with lubricating oil and air to the ball screw nut; and the length of the ball screw nut on the screw shaft In the direction, it is installed on the mobile station at a position closer to the motor side than the center of the mobile station. The machine tool of claim 1, wherein the ball screw nut is installed on the end of the moving table on the motor side in the longitudinal direction of the screw shaft. For example, the machine tool of claim 1 or 2, wherein the moving table is equipped with a spindle that holds and rotates the workpiece, or a tool holder that supports tools for processing the workpiece, and by switching the rotation direction of the screw shaft, The ball screw nut vibrates along the screw shaft to process the workpiece. The machine tool according to any one of claims 1 to 3, wherein the screw shaft faces the horizontal direction.

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