JPH04250903A - Driving mechanism for main spindle of machine tool - Google Patents

Abstract

PURPOSE:To provide a driving mechanism for a main spindle of a machine tool, which is compact in its construction, which withstands both low speed & heavy load operation and high speed rotation, and which does not produce vibration or noise. CONSTITUTION:The system is constituted in such a way that an output shaft 42 of a motor 40 having a winding switching mechanism is provided with a through hole 42a, is supported by a ceramic bearing 44, and is directly connected to a main spindle 50 of a machine tool.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drive mechanism for a main shaft of a machine tool.

0002

[Prior Art] The main spindle of a machine tool is exposed to low-speed, high-load and high-speed rotation, but since the maximum rotational speed of a general drive motor is low, a gear or belt is interposed between the main spindle and the motor to reduce the speed. It required a mechanism and a speed-up mechanism.

0003

However, belts have problems with vibration and slip, and are not suitable for high-speed rotation. Gears also make noise and are not suitable for high speed rotation. Also,
In order to change speed, an intermediate shaft is required between the main shaft and the motor, and residual unbalance in the intermediate shaft, gears, pulleys, etc. becomes a cause of vibration. Furthermore, it lacks compactness due to the presence of deceleration and speed increase mechanisms.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a drive mechanism for a main shaft of a machine tool that is compact, can withstand low-speed, high-load and high-speed rotation, and does not generate vibration or noise.

[0005]

[Means for Solving the Problems] In view of the above object, the present invention provides an output shaft of a motor having a coil switching mechanism, which has a through hole, and which is supported by a ceramic bearing and which is a main shaft of a machine tool. To provide a drive mechanism for a machine tool main shaft, which is characterized in that it is directly connected to a machine tool main shaft.

[0006]

[Operation] Directly connecting the motor and the main shaft of the machine tool eliminates the need for an increase and decrease mechanism, reducing vibration and noise. Furthermore, simply connecting directly will not be able to withstand the low speed, high load and high speed rotation of the main shaft. Therefore, the motor is equipped with a coil switching mechanism so that high output can be obtained even in a low speed rotation range, and furthermore, ceramic bearings are used to prevent bearing seizing caused by high speed rotation. Further, a through hole is provided in the output shaft of the motor in order to allow the cutting fluid to flow through the main shaft and supply the cutting fluid to the machining area at the tip of the main shaft.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in more detail below based on embodiments shown in the accompanying drawings. First, FIG. 2 is a schematic diagram showing a state in which each phase coil in a three-phase AC motor consisting of U, V, and W is star-connected, and FIG. 3 shows the winding structure of only the U phase with reference numbers 1, 2, FIG. 3 is a diagram showing an actual winding structure in relation to the slot positions indicated by 3 and the like. The phase coils U, V, and W are electrically connected at the neutral point XYZ, and the winding structure of the coils in each phase is the same, so only the U phase will be described below.

Both ends of the U-phase coil winding are connected to the neutral point X, respectively.
It is connected to YZ and terminal U1. Here, we are considering an AC motor with 36 slots as an example, and the terminal U
The coils that emitted 1 are slots 1, 12, 2, 11, 3,
10 to constitute the first coil winding X1, and then the slots 19, 30, 20, 29, 21,
28 to form another coil winding X2. Here, the numbers of the slots indicate that the slots are arranged in the circumferential direction in order from the lowest number to the highest number. The coil that has passed through the slot 28 is inserted into the slot 1 again via the terminal U2. Thereafter, the order of the slots through which the coils pass is the same as for the first set of coil windings X1 and X2, forming a second set of coil windings X1' and X2'. The coil passing through the last slot 28 terminates at the neutral point XYZ.

In the above embodiment, for example, the first set of coil windings X1 and X2 are disposed deep in each slot, and the second set of coil windings X1' and X2' are arranged in the openings of each slot. It is located closer to the department. In this embodiment, there is only one terminal, terminal U2, in the intermediate portion, but any number of terminals can be provided by repeating the winding order of the coils as required. In the case of the embodiment shown in FIGS. 2 and 3, if power is supplied through the neutral point XYZ and the terminal U1, all the coil windings X1, X2, X1', and X2' are used. When power is supplied through the neutral point XYZ and the terminal U2, only the coil windings X1' and X2' are energized, and the remaining coil windings X1 and X2 are not energized. As a switching device for these terminals, there is a electromagnetic relay (MCC) or the like.

When power is supplied by current control, under conditions where losses such as Joule heat are ignored, the strength of the magnetic field generated by the U-phase coil is equal to the number of times the coil is inserted through each slot. is proportional to the winding. Therefore, the output power is proportional to the number of turns of the coil and the rotational speed N. Therefore, when using an AC motor in a low speed range, the rotational speed N is small, so in order to obtain high output, the number of coil turns used should be increased, and when used at high speed rotation, the number of coil turns should be small, even if the number of coil turns is small at low speed rotation. You can get the same amount of output as. Therefore, at low rotational speeds N, power is supplied through the terminal U1 and all the coils in the same slot S are used. Further, at a high rotational speed N, in order to obtain an output comparable to that at a low rotational speed, it is sufficient to select and use a terminal having an appropriate number of turns from among a plurality of terminals provided in the middle of the coil. In the case where two terminals are provided for each phase, if the base rotation speeds NL and NH (see Fig. 6) of the low rotation speed range and high rotation speed range that are planned to be used are determined, both of these rotation speeds are determined. The terminal U2 may be set so that the number of coil turns corresponds to the speed ratio. When power is supplied by voltage control, the output changes depending on the current value flowing through the coil wire inserted into each slot, the number of turns of the coil, and the rotation speed N, so the coil wire at both ends of the terminal provided in the middle of the winding is Wire rods having different characteristics, for example, made of different materials may be used.

FIG. 6 illustrates the output characteristics of the AC motor having the coil winding structure according to the present invention shown in FIGS. 2 and 3. A solid line 50 shows a characteristic curve of output P versus rotational speed N when the AC motor is used in a low rotational speed region with a base rotational speed NL, and another solid line 52 shows a characteristic curve of the output P with respect to the rotational speed N in a high rotational speed region with a base rotational speed NH. The characteristic curve of the output P is shown. By switching the coil windings for each phase at the rotational speed NS where the characteristic curves 50 and 52 intersect, output fluctuations can be reduced in the region between the maximum usable rotational speed Nmax and the base rotational speed NL. A small output characteristic indicated by the dashed line 54 is obtained. That is, when using the low rotational speed region, the coil windings X1, X2, X1 in each phase
', and X2' are all used, and only the coil windings X1' and X2' are used in the high rotational speed range.

While FIGS. 2 and 3 show an embodiment in which the coil windings are connected only in series, FIG. 4 shows another embodiment in which both series connection and parallel connection are incorporated. S indicated by a broken line
L represents one slot. That is, if power is supplied from terminal U1, all coil windings A1, A2, A1',
and A2' are used, but if terminal U2 is used, only coil windings A1' and A2' are used, and 1
There is a non-energized coil in each slot SL.

Although FIGS. 2 to 4 are all star connection embodiments, FIG. 5 shows an embodiment of a delta connection. Regarding the U phase, four coil groups X1, X2, X1', and X2 are used as in the case of FIG.
' are connected in series, and one slot has a dashed line S.
Two coil windings (e.g. X1 and X1') as shown by L
A portion of each is inserted and arranged. In this coil winding structure, when the motor is used in a low rotational speed region, the switch SW shown in the figure is closed and the switch SW' is opened.
, V, W are supplied via terminals U1, V1, W1. Further, in a high rotational speed region, switch SW' is closed and SW is opened to supply power from terminals U2, V2, and W2. In the latter case, for the U phase, only the coil windings X1' and X2' are energized.

As is clear from the following explanation, according to the above winding switching mechanism, high output can be maintained over a wide rotational speed range from low rotational speed to high rotational speed simply by switching the connection of the coil winding. . Therefore, if the present invention is applied to spindle motors of machine tools that need to be used in both low rotational speed and high rotational speed ranges, it becomes possible to provide an inexpensive and space-saving drive source. In addition, the terminals provided in the middle of each phase coil winding can be arranged by appropriately selecting the number of coil turns used in each phase coil winding, and can be provided in multiple locations, so it is possible to Set the base rotation speed ratio of each area relatively arbitrarily,
Can be changed.

Next, referring to FIG. 1, the main shaft 5 of the machine tool
0 is coaxially directly connected to the output shaft 42 of the drive motor 40 having the above-mentioned winding switching mechanism via a connecting member 48 such as a well-known span ring.

Further, the output shaft 42 of the motor 40 is supported by a ceramic bearing 44, so that seizure does not occur even during high speed rotation.

The drawbar 52 disposed inside the main shaft 50 is provided with a through hole 52a for supplying machining fluid to the tip of the main shaft 50, and the output shaft center 42 of the motor 40 is also provided with a through hole 52a. 42a is provided, and this output shaft 4
The machining fluid is supplied to the machining area at the tip of the spindle through the through holes through a rotary joint 46 disposed at the rear end of the rotary joint 46. Further, the through hole 42a of the output shaft 42 can also be used when a designed mechanism in which the draw bar 52 is operated from the rear of the motor 40 is adopted.

The drive motor 40 described above is connected to the main shaft 50 without a speed increasing mechanism and is designed to be able to rotate up to the high speed rotation required by the main shaft 50, and the output also meets the specifications of the main shaft 50. It matches. Therefore, heat generation is high, and it is necessary to cool the drive motor 40 efficiently. For this purpose, for example, Japanese Patent Laid-Open No. 2-797 published by the applicant
In some cases, a motor cooling structure as disclosed in Japanese Patent No. 46 may be required.

Furthermore, since the output shaft 42 of the motor and the main shaft 50 of the machine tool are directly connected, if a detector 54 for detecting rotational position etc. is provided on the motor side, there is no need for a detector for the main shaft itself. be.

[0020]

As is clear from the above description, the present invention provides a machine tool spindle drive mechanism that is compact, can withstand low-speed, high-load and high-speed rotation, and does not generate vibration or noise. It becomes possible to provide.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view showing a drive mechanism according to the present invention.

FIG. 2 is a schematic diagram showing a first example of a coil winding structure of a drive motor.

3 is a diagram of a coil winding structure showing one phase of the coil winding structure of FIG. 2 in correspondence with a slot; FIG.

FIG. 4 is a schematic diagram showing a second embodiment of a coil winding structure of a drive motor.

FIG. 5 is a schematic diagram showing a third embodiment of a coil winding structure of a drive motor.

FIG. 6 is an output characteristic graph of a motor having a coil winding structure shown in the first to second embodiments.

[Explanation of symbols]

40...Drive motor 42...Output shaft 42a...Through hole 44...Ceramic bearing 48...Connection member 50...Main shaft

Claims (1)

[Claims] 1. A main shaft of a machine tool, characterized in that the output shaft of a motor having a coil switching mechanism has a through hole, the output shaft is supported by a ceramic bearing, and is directly connected to the main shaft of the machine tool. Drive mechanism.