JPH0445283B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a main shaft structure of a machine tool such as a machining center.

(b) Prior Art Conventionally, in this type of spindle structure, a disc spring that provides a holding force to hold the tool on the spindle has been provided around the drawbar to cover the drawbar.

(c) Problems to be Solved by the Invention However, this requires the drawbar to be longer than the installation length of the disc spring, and this has the disadvantage that the main shaft becomes longer in the axial direction of the main shaft.

In addition, in 15943 of 1977, a disk spring was compressed between the bearings of the bearing assembly on the outer periphery of the main shaft outside the collet that holds the tool, in order to reduce the size of the main shaft in the axial direction. It has been proposed that when a disc spring is installed on the outer periphery of the main shaft, a horizontal hole passing through the inside and outside of the main shaft is drilled through the main shaft in order to transmit the elastic force of the disc spring to the drawbar provided inside the main shaft. However, it becomes necessary to mechanically connect the disc spring outside the main shaft and the internal drawbar. However, since a horizontal hole is drilled in the main shaft that transmits the cutting force, this method inevitably reduces the rigidity of the main shaft, making it unsuitable for heavy cutting. The disadvantage is that the mechanism becomes complicated. Furthermore, since the disk spring is installed between the bearings of the bearing assembly, the positioning member for positioning the bearings can only be installed between the outer rings of the bearings, which only reduces the support rigidity of the bearing assembly as a whole. Another problem is that the length of the bearing assembly in the direction of the spindle axis, which determines the length of the spindle in the direction of the spindle axis, becomes longer due to the presence of the disc spring, making it impossible to reduce the size of the spindle in the direction of the spindle axis.

In order to eliminate the above-mentioned drawbacks, the present invention makes it possible to shorten the length of the drawbar, has a simple structure, can withstand heavy cutting, and also reduces the size in the direction of the spindle axis. The object of the present invention is to provide a main shaft structure that can be supported by a bearing assembly and has high rigidity.

(d) Means for solving the problem That is, the present invention has a fixing member, and positions a main shaft formed in a cylindrical shape on the fixing member in the direction of the main shaft of the bearing with respect to a plurality of bearings. A bearing assembly formed by connecting positioning members in series is rotatably provided through the outer circumferential surface of the spindle, and a tool holder is provided inside the spindle with one end opened at the end of the spindle to hold a tool. In addition to being detachably formed, a drawbar is provided inside the main spindle so as to be movable in the axial direction of the main spindle. A plurality of disc springs are provided so as to be openable and closable in a radial direction with respect to the shaft center, and a plurality of disc springs are provided between the main shaft and the drawbar at the outer periphery of the collet inside the main shaft, directly covering the collet and connected to the bearing. It is constructed by being compressed and inserted inside the assembly.

(e) Effect With the above-described configuration, the present invention allows the disc spring to be inserted into the outer periphery of the collector inside the main shaft inside the bearing assembly, so there is no need to provide the disc spring to cover the drawbar. Since the length of the drawbar is shortened and the disc spring is not interposed between the bearings, the size in the axial direction of the main shaft is reduced.

Further, the drawbar and the disc spring act so as to be directly connected inside the main shaft.

(f) Embodiments Hereinafter, embodiments of the present invention will be described based on the drawings.

FIG. 1 is a front view showing an embodiment of the main shaft structure according to the present invention.

A machine tool 4 such as a machining center has a frame 1, as shown in FIG. A main shaft 3 is rotatably supported. The bearing assembly 8 is
It has two bearings 2 each arranged in series in the directions of arrows A and B, which are the axial directions of the main shaft, and sleeves 8a and 8b interposed between them to position the bearings in the axial direction of the main shaft. ing.
Inside the main shaft 3 formed into a cylindrical shape, a tool holder 3a formed in a conical shape is formed with one end opened at the end of the main shaft so that a tool 13 can be attached and detached. A tool holding mechanism 5 is provided on the right side of the figure. The tool holding mechanism 5 is the main shaft 3
It has a drawbar 6 which is provided with its tip fitted inside, and is movable in the directions of arrows A and B, which are the directions of the three axes of the main shaft, and is provided so as to be rotatable together with the main shaft 3. That is, at the left end in the figure, the pusher 7 has its tip 7a attached to the tool holding portion 3a.
They are screwed together in such a way that they protrude towards. Inside the main shaft 3 between the pusher 7 and the drawbar 6, a collet 9 is provided with an engaging pawl 9a at its tip that can be opened and closed in a radial direction with respect to the main shaft axis. , a plurality of disc springs 10 are compressed and installed inside the main shaft 3 between the main shaft 3 and the drawbar 6 so as to directly cover the collet 9 and are inserted inside the bearing assembly 8. A ring 11 is fitted between the disc spring 10 at the left end in the figure and the main shaft 3, and an inclined surface 11a is formed on the tool holding portion 3a side of the ring 11.
A drive gear 12 for driving the main shaft 3 is fitted to the right end of the outer circumference of the main shaft 3, and the drive gear 12 is connected to a driving means such as a drive motor (not shown).

On the other hand, the tool 13 mounted on the main spindle 3 has a tool holder 13a, and the tool holder 13a is formed with a tapered shank portion 13b formed in a conical shape so as to be in close contact with the tool holding portion 3a. . Note that a pull stud 13c is formed at the right end of the tapered shank portion 13b.

Since the machine tool 4 etc. has the above configuration, when mounting the tool 13 on the main spindle 3, first drive an actuator such as a hydraulic cylinder (not shown) to move the drawbar 6 along with the pusher 7 and the collector 9. It is moved in the direction A against the elasticity of the disc spring 10. Then, the tip of the collet 9 is pushed out in the direction A, and the engaging pawl 9a is opened outward with respect to the main shaft axis. In this state, when the tool 13 is inserted and set into the tool holding part 3a by fitting the pull stud 13c, and then the drawbar 6 is returned in the direction B using the elasticity of the disc spring 10, the pusher 7 and the collet 9 are also moved to B. The engaging pawl 9a of the collet 9 is guided by the inclined surface 11a of the ring 11, converges in the direction of the main shaft axis, and engages with the pull stud 13c. Since the collet 9 moves in the direction B due to the elasticity of the disc spring 10 even after the engaging claw 9a engages with the pull stud 13c, the tool 13
is moved in the direction B by the collet 9, and the taper shank portion 13b of the tool 13 contacts the tool holding portion 3a of the spindle 3 with a predetermined contact pressure, whereby the tool 13 is securely held on the spindle 3. Ru.

In this state, when the drive gear 12 is rotationally driven via a drive means such as a drive motor, the rotation of the drive gear 12 is transmitted to the tool 13 via the main shaft 3, and the tool 13 performs a predetermined processing.

When the tool 13 is replaced after machining is completed, the drawbar 6, together with the pusher 7 and the collect 9, is moved in the direction A against the elasticity of the disc spring 10. Then, the engaging claw 9a of the collet 9 is released outward to release the engaged state with the pull stud 13c, and then the tip 7a of the pusher 7 comes into contact with the right end surface of the pull stud 13c in the drawing. Since the pusher 7 continues to move in the A direction, the tool 13 moves in the A direction while being pushed by the pusher 7, and the close contact between the taper shank portion 13b and the tool holding portion 3a is also released, and the tool 13 is moved to the main shaft. 3, it is ready to be removed. Therefore, it is not shown.
The tool 13 in the spindle 3 is removed using an ATC device, etc., and the tool 13 to be used next is replaced with the tool 13 on the spindle 3.
, install it according to the procedure described above and continue machining.

(g) Effects of the Invention As described above, according to the present invention, the main shaft 3, which has a fixed member such as the frame 1 and is formed in a cylindrical shape, is connected to a plurality of bearings 2 and the bearings. A bearing assembly 8 formed by connecting positioning members such as sleeves 8a and 8b in series for positioning in the direction of the main shaft is provided rotatably through the outer peripheral surface of the main shaft 3, and a tool is mounted inside the main shaft. The holding part 3a is formed with one end opened at the end of the main shaft so that the tool 13 can be attached and detached, and a draw bar 6 is provided inside the main shaft so as to be movable in the axial direction of the main shaft. A collet 9 capable of engaging with a tool mounted on the tool holder is provided so as to be freely openable and closable in a radial direction with respect to the spindle axis by the drawbar, and a collet 9 is provided between the spindle and the drawbar at the outer periphery of the collet inside the spindle. In addition, since a plurality of disc springs 10 are compressed and arranged so as to directly cover the collet and to be inserted inside the bearing assembly, the disc springs can
Since it is housed within the main shaft, there is no need to provide a disc spring to cover the drawbar, and the length of the drawbar can be shortened accordingly. In addition, since the disc spring is directly covered with the outer circumference of the collet and inserted inside the bearing assembly, the bearing assembly and disc spring overlap in a direction perpendicular to the spindle axis. This eliminates the need for a disc spring in the bearing assembly, making it possible to shorten both the dimensions of the main shaft including the drawbar and the main shaft itself in the direction of the main shaft axis. By eliminating the spring, the supporting rigidity of the main shaft by the bearing assembly can be improved.

Furthermore, since the disc spring 10 and the drawbar 6 are connected inside the main shaft 3, a horizontal hole is bored in the main shaft 3 to connect the drawbar and the disc spring, so that the disc spring provided on the outer periphery of the main shaft and the inside of the main shaft are connected. There is no need to connect the drawbar of the machine through the horizontal hole, which not only simplifies the structure of the main shaft, but also eliminates the need to form cutouts such as horizontal holes on the main shaft, which can be an obstacle to transmitting cutting force. Since this eliminates the problem, it becomes possible to provide a spindle structure that can withstand heavy cutting.

[Brief explanation of drawings]

FIG. 1 is a front view showing an embodiment of the main shaft structure according to the present invention. 3... Main shaft, 5... Tool holding mechanism, 6... Drawbar, 9... Collet, 10... Disc spring, 13
……tool.

Claims (1)

[Scope of Claims] 1. A fixed member having a cylindrical main shaft formed in the fixed member, and a plurality of bearings and a positioning member for positioning the bearing in the main shaft direction connected in series. A bearing assembly is provided rotatably through the outer circumferential surface of the main spindle, and a tool holding portion is formed inside the main spindle with one end opened at the end of the main spindle so that the tool can be attached and detached; A drawbar is provided movably in the axial direction of the main spindle, and a collet capable of engaging with a tool mounted on the tool holder is provided inside the main spindle and can be freely opened and closed in a radial direction with respect to the main spindle axis by the drawbar. further provided at the outer periphery of the collector inside the main shaft,
A main shaft structure in which a plurality of disc springs are contracted between the main shaft and the drawbar in a manner that directly covers the collector and is inserted inside the bearing assembly.