JP2001198757A - Spindle of machine tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To simplify and miniaturize a machine tool, in particular, a feeding device of a spindle. SOLUTION: An expansion means for changing the distance between a supported part 14 of a spindle 10 supported on a main bearing 12 and a chuck 18 for holding a tool 20 is provided between them. The expansion means is provided with a guide rod 22 fixed to the part to be supported 14, and a sleeve 24 fixed to the chuck 18. The sleeve 24 is provided with a cylindrical part 26, and the guide rod 22 is inserted in it. A linear bushing 28 is provided in a radial clearance between the guide rod 22 and the sleeve 24 to allow the movement of the sleeve 24 along the spindle axis A. An actuator 32 for driving the sleeve 24 in the axis A direction is provided. The actuator 32 comprises an actuator coil 36 and a permanent magnet 34, and force in the axis A direction is generated by electric current flowing to the coil and magnetic force of the permanent magnet.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a machine tool,
In particular, the present invention relates to a spindle structure for holding and rotating a tool or a workpiece.

[0002]

2. Description of the Related Art A spindle of a machine tool holds and rotates a tool or a workpiece. This rotation causes a cutting motion of the relative motion between the tool and the workpiece. The tool and the workpiece also perform a relative motion, ie, a feed motion, for machining a new position one after another. This feed movement conventionally moves the entire headstock provided with a main bearing that supports the spindle, or fixes the headstock, and fixes the blade or workpiece on a table that moves relative to the main spindle. It was caused by moving the platform. On a table that moves relative to the spindle, for example,
A tool post on a lathe corresponds to this.

[0003]

When a headstock or a tool post is to be moved, these tables themselves are heavy, so that the table on which the table moves must be strong, resulting in an increase in the size of the apparatus. was there. In addition, there is also a problem that driving a heavy object is not suitable for high-speed movement.

An object of the present invention is to solve the above-mentioned problems, and an object of the present invention is to provide a spindle of a machine tool capable of performing a feeding motion with a small and lightweight mechanism.

[0005]

In order to solve the above-mentioned problems, a spindle of a machine tool according to the present invention holds a tool or a workpiece and rotates it, and is supported by a main bearing. A supported part to be held, a holding part for holding a tool or a workpiece, and a telescopic means provided between the supported part and the holding part, for changing a distance of these parts in a spindle axial direction, Transmission means for transmitting the rotational driving force from the supported portion to the holding portion.

[0006] Since it expands and contracts with the spindle itself, the feed motion can be performed without moving the headstock or the like.

Specifically, the expansion / contraction means includes a guide rod fixed to the supported portion, a sleeve fixed to the holding portion and arranged to surround the guide rod, Bearing means disposed in the radial gap of the sleeve to allow at least their relative axial movement.

By providing the bearing means, the feed movement can be performed smoothly and accurately.

Further, specifically, the transmitting means has one end coupled to the supported part and the other end coupled to the holding part, and is extendable and contractible in the spindle axis direction and substantially indeformable in the rotational direction. Bellows.

Further, the transmitting means and the bearing means may be
It can be a ball spline. The ball spline allows axial relative movement of the coaxially arranged guide rod and sleeve, while preventing relative movement in the circumferential direction. Therefore, a single component can serve as both the transmission means and the bearing means, resulting in a simpler configuration.

Further, the spindle may have an actuator for controlling a movement of the holding portion with respect to the supported portion in a spindle axial direction. The actuator may include a permanent magnet fixed to the sleeve and axially magnetized, and a coil fixed to the main bearing outside the sleeve and fixed to a main bearing and having a spindle axis as a center axis. . Further, the actuator may be an induction linear motor having at least a part of the sleeve as conductive, using this as a mover, and having a stator disposed outside the sleeve and forming a moving magnetic field in a spindle axial direction. Can also. Further, it is preferable that the actuator is formed symmetrically with respect to a spindle axis so as not to generate a thrust in a rotational direction.

Further, the spindle may be provided with position detecting means for detecting a position of the holding portion with respect to the supported portion in a spindle axial direction. The position detecting means can be, for example, a differential transformer type or an optical position sensor having an optical slit.

[0013]

Embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings. FIG.
FIG. 2 is a diagram illustrating a schematic configuration of a spindle according to the embodiment. The spindle 10 has a supported portion 14 supported by a main bearing 12, and is rotatably held by a headstock 16. A tool 20 such as a drill is held on a chuck 18 at the tip of the spindle 10. Therefore, the chuck 18 functions as holding means for holding the tool.

Between the supported portion 14 and the chuck 18,
An expansion / contraction mechanism for expanding / contracting the distance in the direction of the spindle axis A and a transmission mechanism for transmitting the rotation of the supported portion 14 driven by a driving mechanism (not shown) to the chuck 18 are provided.

A guide rod 22 extends from the supported portion 14 along the spindle axis A. On the other hand, the chuck 18
Is fixed to the tip of the sleeve 24. Sleeve 24
A substantially cylindrical portion 26 is coaxial with the guide rod 22,
It is arranged to surround it. Also, the sleeve 24
A linear bushing 28 is disposed as a bearing between the and the guide rod 22, and relative movement of the sleeve 24 and the guide rod 22 at least in a direction along the spindle axis A is allowed. Two ends of the bellows 30 are connected to the supported portion 14 and the sleeve 24, respectively.
The bellows 30 is deformable in the direction of the spindle axis A and allows the distance between the supported portion 14 and the sleeve 24 to be changed. The displacement of the sleeve 24 in the rotation direction is not caused. Thus, the rotation of the supported portion 14 is transmitted to the sleeve 24 via the bellows 30.

The present embodiment further includes an actuator 32 for driving the chuck 18 with respect to the supported portion 14 in the spindle axial direction. The actuator 32 includes a cylindrical permanent magnet 34 fitted on the outer periphery of the sleeve 24.
And an annular actuator coil 36 arranged outside the permanent magnet 34 so that the spindle axis A coincides with the spindle axis A. The actuator coil 36
It is fixed to the headstock 16 and is fixedly arranged on the inner surface of a substantially cylindrical outer cylinder 38 arranged so as to further surround the outside of the sleeve 24. The permanent magnet 34 is magnetized in the direction of the spindle axis A, and an actuator core 40 formed of a magnetic material at both ends thereof and having a slightly larger outer shape than the permanent magnet 34 is arranged. Actuator core 40
Are arranged near the center of the dimension of the actuator coil 36 in the direction of the spindle axis A. By arranging such an actuator core 40, the lines of magnetic force can be concentrated on the core, and the leakage magnetic flux can be reduced. The outer cylinder 38 is formed of a magnetic material,
This also reduces leakage of lines of magnetic force.

When currents in opposite directions are applied to the two actuator coils 36, forces in the direction of the spindle axis A are generated in the same direction in the two sets of the actuator core 40 and the coil 36, and the sleeve 24 That is, the tool 20 can be moved. By this movement, feed during processing can be performed. Further, as described above, since the actuators 32 are arranged symmetrically with respect to the spindle axis A, no force is generated in the direction perpendicular to the axis A and no torque is generated around the axis A.

Further, in the present embodiment, the supported portion 14
Has a position detecting means for detecting the position of the chuck 18 in the direction of the spindle axis A with respect to. Sleeve 24
An annular transformer core 42 made of a magnetic material is
Is inlaid. A transformer coil is arranged on the inner surface of the outer cylinder 38 so as to face this. The transformer coil includes one excitation coil 44 and two induction coils 46 arranged so as to sandwich the excitation coil 44 in the direction of the axis A. When an alternating current flows through the exciting coil 44, an induced current flows through the induction coil 46. The amplitude of this induced current is
2 and it depends on the relative position of each transformer coil.
The relative position between the transformer core and the coil, that is, the position of the chuck 18 with respect to the supported portion 14 can be calculated from the difference between the amplitudes of the two induced currents. Further, the transformer core 42 has a symmetrical shape with respect to the spindle axis A, so that the rotation of the spindle 10 does not affect the induced current.

As described above, the displacement of the chuck 18, ie, the tool 20, is calculated from the output of the induction coil 46. Further, the tool position is fed back based on the calculated value, and the control unit (not shown)
6 is controlled to control the advance and retreat of the tool.

FIG. 2 is a diagram showing a schematic configuration of another embodiment. For a similar configuration of the embodiment shown in FIG.
The same reference numerals are given and the description is omitted. The features of this embodiment are the bearing means interposed between the guide rod 22 and the sleeve 24 and the transmission means for transmitting torque from the supported portion 14 to the chuck 18. In the present embodiment, as these means, a ball spline 48 is used, which is rigidly connected to the sleeve 24 and disposed in a gap between the guide rod 22 and the sleeve 24 in the radial direction. A ball 50 as a rolling element of the ball spline 48 has a peripheral circuit formed by a straight path parallel to the spindle axis A provided on the raceway cylinder 52 of the ball spline 48 and a curved path connecting the ends of the straight path. It is possible to go around. The ball on the straight road is the guide rod 2
The two surfaces are also in contact with spline grooves 54 provided parallel to the spindle axis A. The balls in the peripheral circuit are not in contact with the guide rod 22. The ball that comes into contact with the spline groove 54 prevents the relative rotation of the race tube 52 and the guide rod 22. Thereby, the supported portion 1
4 rotates the guide rod 22, the ball spline 48
And via the sleeve 24 to the chuck 18. Spline shaft A of guide rod 22 and sleeve 24
Regarding relative movement in the direction, the ball goes around the circuit in response to this relative movement and does not prevent it. Such a straight path is n times around the spindle axis (n is 3 times).
2n lines are symmetrically arranged at equal intervals symmetrically, and a pair is formed by two adjacent lines to prevent clockwise or counterclockwise rotation.

FIG. 3 is a diagram showing a schematic configuration of still another embodiment. 1 and 2 are denoted by the same reference numerals, and description thereof will be omitted.
The characteristic point of this embodiment lies in the configuration of the position detecting means. The position detecting means of this embodiment uses an optical scale 56. High reflectivity metal such as chrome is sputtered on a part of the outer surface of the sleeve 24. Further, an annular groove is formed on this surface by cutting or the like, and a number of grooves are formed in the spindle axis A direction.
Thus, an optical slit 58 in which portions having different reflectivities are alternately formed. An optical head 60 is arranged at a position of the outer cylinder 38 facing the optical slit 58. The optical head 60 irradiates the optical slit 58 with light, and outputs the intensity of the reflected light as an electric signal. When the sleeve 24 moves in the direction of the spindle axis A with respect to the outer cylinder 38, the optical head 60 outputs a signal that changes in strength according to the stripes of the optical slit 58.
By counting the number of strengths of the signal, it is possible to calculate how many slits the optical head 60 has passed, that is, the amount of movement of the sleeve 24 and the chuck 18. The positions of the chuck 18 and the tool 20 are controlled by feeding back the movement amount.

The optical head 60 has at least two light receiving elements, and these light receiving elements are displaced in the axial direction. Thereby, the direction of movement of the sleeve can be known. This axial displacement is caused by the optical slit 58.
Is preferably 1/4 of the slit interval. Also,
The optical slit 58 is arranged symmetrically with respect to the spindle axis A, and does not receive rotation of the sleeve 24.

FIG. 4 is a diagram showing a schematic configuration of still another embodiment. The same components as those in the above-described embodiment are denoted by the same reference numerals, and description thereof will be omitted. The feature of this embodiment lies in the configuration of the actuator. The actuator of the present embodiment has the same configuration as that of the induction type linear motor. On the outer periphery of the sleeve 24, a magnetic core 62 having a cylindrical shape and having conductivity is firmly connected. Further, annular strips 64 having high conductivity are formed at equal intervals on the movable element core 62.
On the inner wall of the outer cylinder 38, a stator coil 66 corresponding to three phases is arranged at a position facing the moving element core 62. By supplying the three-phase AC power to the stator coil 66, an induced current is generated in the mover core 62, and a force in the direction of the spindle axis A is generated. Regarding this AC power, the detected value of the position detecting means is fed back, and control is performed based on the feedback.

The components of each embodiment described above can be interchanged with each other. For example, FIG.
In the embodiment shown in FIGS.
Instead, a bellows 30 and a linear bushing 28 may be provided.

[Brief description of the drawings]

FIG. 1 is a diagram showing a schematic configuration of the present embodiment.

FIG. 2 is a diagram showing a schematic configuration of another embodiment.

FIG. 3 is a diagram showing a schematic configuration of still another embodiment.

FIG. 4 is a diagram showing a schematic configuration of still another embodiment.

[Explanation of symbols]

10 spindles, 12 main bearings, 14 supported parts,
18 chuck, 20 tools, 22 guide rod, 24
Sleeve, 28 linear bushing, 30 bellows,
32 actuator, 34 permanent magnet, 36 coil, 38 outer cylinder, 40 core, 42 transformer core (differential transformer type position sensor), 44 excitation coil (differential transformer type position sensor), 46 induction coil (differential transformer type position) Sensor), 48 ball spline, 56 optical scale (optical position sensor).

Claims (11)

[Claims] 1. A spindle for holding a tool or a workpiece and rotating the same, comprising: a supported portion supported by a main bearing; a holding portion for holding a tool or a workpiece; and the supported portion. A spindle which is provided between the holding part and the holding part, and which extends and contracts means for changing a distance between these parts in the spindle axial direction, and a transmission means for transmitting a rotational driving force from the supported part to the holding part. . 2. The spindle according to claim 1, wherein the expansion / contraction means is fixed to the supported portion, and is fixed to the holding portion, and is arranged to surround the guide rod. A spindle, comprising: a sleeve; and bearing means disposed in a radial gap between the guide rod and the sleeve to allow at least relative movement in the axial direction. 3. The spindle according to claim 2, wherein the transmission means has one end coupled to the supported part and the other end coupled to the holding part, and is extendable and contractible in a spindle axial direction, and is rotatable. A spindle which is a substantially non-deformable bellows. 4. The spindle according to claim 2, wherein
The spindle, wherein the transmission means and the bearing means are ball splines. 5. The spindle according to claim 1, further comprising an actuator for controlling a movement of the holding portion with respect to the supported portion in a spindle axial direction. 6. The spindle according to claim 5, wherein the actuator is fixed to the sleeve, and a permanent magnet that is magnetized in an axial direction, and is fixed to a main bearing outside the sleeve. And
A coil having a spindle axis as a central axis. 7. The spindle according to claim 5, wherein the actuator has at least a part of the sleeve conductive, uses the movable member as a mover, and is disposed outside the sleeve to move in a spindle axial direction. A spindle, which is an induction linear motor having a stator that creates a magnetic field. 8. The spindle according to claim 5, wherein
The spindle, wherein the actuator is formed symmetrically with respect to a spindle axis. 9. The spindle according to claim 1, further comprising: a position detection unit configured to detect a position of the holding portion with respect to the supported portion in a spindle axial direction. 10. The spindle according to claim 9, wherein said position detecting means is a differential transformer type position sensor. 11. The spindle according to claim 9, wherein said position detecting means is an optical position sensor of a type having an optical slit.