JPH1015769A - Vertical movement driving device for spindle head - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the rigidity of a vertical movement driving system for vertically moving a spindle head and the accuracy in locating the spindle head. SOLUTION: A vertical movement driving device vertically shifts a spindle head 3 of a machine tool which has the spindle head 3 supporting rotatably the spindle S and a column guidingly supporting the spindle head 3 along guides 1b, 1b in a vertically movable manner. The driving device is constituted of a plurality of screw shafts 12, 12 provided on both side near the axis S of the spindle inside the guides 1b, 1b and parallel to the guides 1b, 1b and of nuts 14a, 14b threadingly inserted into the respective screw shafts 12, 12 and mounted to the spindle head 3 to vertically move the spindle heas 3 along the guides 1b, 1b by the rotation of the screw shafts 12, 12, and of a drive body rotating the screw shafts 12, 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a machine tool having a spindle head that moves up and down along a column, and performs precise positioning when the spindle head is moved up and down and performs smooth lifting and lowering operations at high speed. The present invention relates to a drive device for raising and lowering a spindle head.

[0002]

2. Description of the Related Art Generally, in a machine tool such as a horizontal machining center having a spindle head that moves up and down along a column, a ball screw mechanism is used to move the spindle head to a precise position when the spindle head is moved up and down. I try to go up and down. By the way, in the above-mentioned conventional machine tool, a mechanism including a set of ball screws and a servomotor (drive body) for controlling the rotational positioning of the ball screws is provided at a position separated by a predetermined distance from the spindle axis. If a ball screw mechanism is provided at a position away from the axis by a predetermined distance, a torsional moment is generated around the axis of the spindle when the spindle head is raised and lowered, and a bending moment acts on the screw shaft due to the torsional moment. . When a bending moment acts on the screw shaft, the screw shaft bends to lower the positioning accuracy. Therefore, it is most desirable to provide a ball screw mechanism on the spindle axis. However, the spindle is rotatably supported at the center of the spindle head, and a rotation transmission mechanism such as a gear for transmitting rotation from a driving body (motor) to the spindle is incorporated. Providing a screw shaft on the wire is very difficult in practice.

On the other hand, in Japanese Utility Model Laid-Open No. 5-60748,
There has been proposed a machine tool in which a screw shaft of a ball screw mechanism is connected directly above the center of gravity of a spindle head. This actual opening 5-
The machine tool proposed in Japanese Patent No. 60748 is excellent in that no torsional moment acts around the spindle axis when the spindle head is moved up and down. However, this machine tool has a structure in which a spindle head is suspended by a single screw shaft, and the screw shaft is supported by one point of a nut rotatably provided at an upper end of a column. Therefore, there is a disadvantage that the rigidity of the lifting drive system including the ball screw mechanism is low. As a result, the screw shaft is deformed (elongation, contraction, bending, etc.) due to the load applied to the spindle head or changes in temperature.
However, high-precision positioning cannot be expected. In addition, since this machine tool has a structure in which a long screw shaft moves up and down as the spindle head moves up and down, it also has a drawback that the overall height of the machine tool increases.

[0004]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and is disclosed in Japanese Utility Model Laid-Open No. 5-607.
No disadvantages such as the machine tool proposed in JP 48
By increasing the rigidity of the lifting drive system that raises and lowers the spindle head, and by minimizing the effects of the load and temperature changes acting on the spindle head on the screw shaft, high-precision positioning is achieved when the spindle head is raised and lowered It is an object of the present invention to provide a spindle head lifting / lowering device which enables the above.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a spindle head lifting / lowering drive device according to the present invention comprises a spindle head rotatably supporting a spindle, and a spindle head which can be moved up and down along a guide. A lifting and lowering drive for moving the spindle head up and down in a machine tool having a column that guides and supports a pair of screw shafts provided parallel to the guide on both sides near the spindle axis inside the guide. A nut that is screwed into each of the screw shafts, is attached to the spindle head, and raises and lowers the spindle head along the guide by rotation of the screw shaft, and a driving body that rotates the screw shaft. It is characterized by. The driving body may be provided at one end of the screw shaft such that the axis of the output shaft coincides with the axis of the screw shaft, and control means for synchronously controlling the driving of the driving body may be provided. Further, the screw shaft may be disposed at an equal distance from the spindle axis, or may be provided near an axis orthogonal to the spindle axis, passing through the center of gravity of the resistance force when the spindle head is moved up and down. Is also good. Further, the column on which the guide is formed, the spindle head and the screw shaft may be formed symmetrically in the left-right direction when viewed from the front.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A preferred embodiment of a spindle head elevating mechanism according to the present invention will be described below with reference to the drawings. FIG. 1 is a view for explaining a configuration of an elevation drive device for a spindle head according to an embodiment of the present invention, and FIG.
FIG. 3 is a view taken in the direction of arrows II and II in FIG. 2. In the following description, a horizontal machining center will be described as an example of a machine tool. However, the present invention can be applied to other machine tools having a spindle head that moves up and down along a column. It is possible.

[Explanation of Column] As shown in FIG. 1, in this embodiment, a Z-axis guide 2a is provided on a bed 2 of a machine tool in a direction perpendicular to the paper surface of FIG. A column 1 that can move freely is provided upright. In the space of the column 1, a spindle head 3 that can move up and down is provided. The column 1 has a box-shaped double wall on the side, and is symmetrical in a front view (the state shown in FIG. 1).

[Description of Spindle Head] As shown in FIG.
The spindle head 3 includes a spindle head main body 6 that rotatably supports the spindle S, a spindle rotation motor 8 provided behind the spindle head main body 6, and a guide portion provided at the center of the spindle head main body 6. 7 are schematically constituted. Guide 7
Guide grooves 7a, 7a are formed on both sides of the guide rail, and a guide rail (guide) 1 formed in the guide grooves 7a, 7a.
The fitting of b and 1b guides the elevation of the spindle head 3. In this embodiment, the guide grooves 7a, 7a of the guide portion 7 restrict the guide rails 1b, 1b from four sides, and regulate the main spindle head 3 from moving in a plane orthogonal to the vertical direction. This is for the purpose of performing precise positioning of the spindle head while eliminating the displacement of the spindle head in a plane orthogonal to the vertical direction. In addition, the feed amount is distributed and received by the guide rails on both sides.

[Explanation of the Elevation Driving Device for the Spindle Head] The spindle head 3 configured as described above is a
(See FIG. 1) to move up and down along the column 1. Less than,
The configuration of the lifting drive device 10 that raises and lowers the spindle head 3 will be described.

[Description of Ball Screw Mechanism] Guide Rail 1
b, 1b, screw shafts 12, 1 of two ball screws parallel to the guide rails 1b, 1b on both sides of the spindle axis Z.
2 are provided. Two nuts 14a, 14b are screwed into the screw shafts 12, 12, respectively. The nuts 14a, 14b are attached to the spindle head main body 6 with bolts 14b. The two nuts 14a, 14b
They are connected in a double nut system with a certain preload applied to eliminate backlash.

The upper and lower ends of the screw shafts 12, 12 are rotatably supported by bearings 13a provided on the upper mounting portion 5a of the column 1 and bearings 13b provided on the lower mounting portion 5b. Motors M, M, which are drivers for raising and lowering the spindle head 3, are attached to the upper attachment portion 5a. Servo motor (hereinafter referred to as motor) M, M
Are mounted so that the axes of the output shafts Ma, Ma coincide with the axes of the screw shafts 12, 12, and the output shafts Ma, Ma are connected to the screw shafts 12, 1 via the couplings 11, 11.
2 is connected to the upper end. According to this aspect, when the output shafts Ma, Ma of the motors M, M rotate, the rotation is transmitted to the screw shafts 12, 12 via the couplings 11, 11, and rotates the screw shafts 12, 12. The motors M, M are provided with detecting means (such as an encoder) for position feedback and speed feedback. On the other hand, retainers 9, 9 are screwed to lower ends of the screw shafts 12, 12, and by tightening the retainers 9, 9, the screw shafts 12, 12 are tightened.
Are given a constant preload. As described above, the constant preload is applied to the screw shafts 12, 12 because the axial deformation of the screw shafts 12, 12 due to a temperature change, a load at the time of elevating the spindle head 3, etc., is absorbed, and high precision is achieved. This is to enable positioning.

A rotation transmitting mechanism such as a gear for transmitting the driving force of the motor 8 to the main shaft S is built in the main body 6 of the main spindle. It is desirable to provide as close as possible. Further, in order to equalize the loads applied to the respective screw shafts 12, 12, it is desirable that the distances from the screw shafts 12, 12 to the main axis S are equal. Further, in FIG. 2, reference symbol G indicates a substantially center of gravity position when the spindle head 3 moves up and down, and the screw shafts 12, 12 pass through the center of gravity position G and the spindle axis Z.
It is desirable to provide it at a position as close as possible to the axis X perpendicular to the axis.

As shown in FIGS. 2 and 3, in this embodiment, the screw shafts 12, 12 are arranged so that the distance from the main shaft axis Z is substantially equal, and It is located near. Therefore, in this embodiment, the load applied to the spindle head 3 can be evenly distributed to the two screw shafts 12 and 12 and is applied to the screw shafts 12 and 12 when the spindle head 3 is moved up and down. The bending moment can also be made very small. As shown in FIG. 1, in this embodiment, a column 1, a spindle head 3, a guide 1b provided on the column 1,
1b, the screw shafts 12, 12, and the motors M, M are formed in a left-right symmetric structure when viewed from the front.

[Description of Driving Body] As described above, in this embodiment, the screw shafts 12, 12 are rotated by driving the motors M, M provided at one ends thereof. Each nut 14a, 1 screwed into the screw shaft 12, 12
The motors M, M need to be driven under synchronous control in order to move the motor 4b up and down evenly, but the synchronous drive control of the motors M, M is performed by a command signal of a numerical controller (not shown). In this case, one of the two motors M, M is a driving side (master axis) and the other is a driven side (slave axis), and the driven side motor M is driven based on a driving command of the driving side motor M. The driving may be controlled, or the deviation between the two motors M, M may be constantly detected and the driven motor M may be corrected so as to reduce the deviation.

[Explanation of Function] Next, the operation of the spindle head lifting / lowering drive device of the present invention having the above-described structure will be described. When the spindle head 3 is moved up and down, the driving bodies M and M are driven synchronously by a movement command signal from a numerical controller (not shown). Therefore, the moving distance of the nuts 14 along the screw shafts 12 is always the same. In this case, nuts 14a, 14 screwed into the screw shafts 12, 12
Since b moves the spindle head 3 up and down evenly from both sides, almost no torsional moment acts on the spindle head 3. Therefore, the bending moment applied to the screw shafts 12, 12 becomes extremely small, and deformation (particularly, bending) of the screw shafts 12, 12 when the spindle head 3 is moved up and down can be almost eliminated.

In the case where the screw shafts 12, 12 are provided at an equal distance from the spindle axis Z, the load applied to the spindle head 3 is evenly distributed to the two screw shafts 12, 12. , 12 can be eliminated. Further, if the screw shafts 12, 12 are provided near or on the axis X passing through the center of gravity G, the load applied to the center of gravity G when the spindle head 3 is moved up and down is reduced. Can be made extremely small. As described above, by minimizing the deformation of the screw shafts 12, 12 when raising and lowering the spindle head 3, the spindle head 3 can be positioned with high accuracy.

Although the preferred embodiment of the present invention has been described, the present invention is not limited to the above embodiment. For example, in the above embodiment, the guide surface (guide, guide groove) is described as a sliding guide surface, but may be a rolling linear motion guide surface (linear guide).

[0018]

According to the present invention, as described above, the rigidity of the lifting drive system for raising and lowering the spindle head can be increased as a whole, and when the spindle head is raised and lowered, a load is applied to the spindle head. In this way, it is possible to minimize the influence of a change in load or temperature on the screw shaft as much as possible, thereby improving the positioning accuracy when the spindle head is moved up and down. Also,
Since the configuration including the guide rail and the ball screw mechanism is symmetrical when viewed from the front, smooth movement can be achieved even during high-speed movement.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a configuration of a spindle head elevating drive device according to an embodiment of the present invention.

FIG. 2 is a view taken in the direction of arrows II in FIG. 1;

FIG. 3 is a view taken in the direction of arrows II-II in FIG. 2;

[Explanation of symbols]

 S spindle Z spindle axis G center of gravity position X axis M motor (drive body) 1 column 1b guide 2 bed 2a guide 3 spindle head 5a upper attachment member 5b lower attachment member 6 spindle head main body 7 guide section 7a guide groove 8 motor 9 retainer 10 Elevating drive device 11 Coupling 12 Screw shaft 13a, 13b Bearing 14a, 14b Nut

Claims (5)

[Claims] 1. A spindle head (3) rotatably supporting a spindle (S), and guides (1b, 1b) for guiding the spindle head.
A lifting / lowering drive device (10) for moving the spindle head up and down in a machine tool having a column (1) for guiding and supporting the same so as to be able to move up and down along the guides (1b, 1b).
A pair of screw shafts (12, 12) provided in parallel with the guide on both sides near the main shaft axis (S) inside of the main shaft, and each of the screw shafts is screwed into the main shaft head (3). A nut (14a, 14a) which is attached and moves the spindle head up and down along the guide by rotation of the screw shaft.
b) and a driving body (M, M) for rotating the screw shaft. 2. The driving body is provided for each of the screw shafts, and is connected to the screw shaft so that an axis of an output shaft coincides with an axis of the screw shaft, and controls driving of each of the driving bodies. The drive device according to claim 1, further comprising control means for performing synchronous control. 3. The drive device according to claim 1, wherein the screw shaft is disposed at an equal distance from the spindle axis. 4. The screw shaft is provided near or on the axis (X) passing through the center of gravity (G) of the resistance force when the spindle head moves up and down and orthogonal to the spindle axis (Z). The lifting drive of the spindle head according to any one of claims 1 to 3, wherein: 5. The apparatus according to claim 1, wherein the column on which the guide is formed, the spindle head, and the screw shaft are formed symmetrically in a left-right view when viewed from the front. A drive device for raising and lowering the spindle head as described in the above.