JP5311253B2 - Machine tool spindle drive - Google Patents

Description

  The present invention relates to a spindle drive device for a machine tool that transmits rotation of a drive shaft of an electric motor to a spindle of a machine tool to rotate the spindle.

Machining centers, in particular machine tools, have a wide variety of workpieces to be cut, and the main spindle has a wide range of torques from high torque for heavy cutting of steel to high rotational speed for machining light alloys such as aluminum at high speed. It is required to realize the rotation speed.
In recent years, in this machining center, the main shaft and the motor are directly connected or the built-in type in which the motor is integrated in the main shaft has become the mainstream, and in order to realize a wide range of torque and rotation speed, the motor It tends to make itself large. However, in this case, energy consumption increases as the capacity of the motor increases, which is not preferable from the viewpoint of energy saving.

  Therefore, in order to realize a wide range of torque and rotational speed while keeping the capacity of the motor low, conventionally, for example, a winding whose number of poles is changed by switching the winding method on the stator side of the motor (three-phase induction motor). There has been proposed a spindle driving device of a switching system or a gear switching system in which the rotation of the electric motor is transmitted to the main shaft via a gear and the gear can be switched in a plurality of stages.

  For example, as shown in Patent Document 1, the former winding switching type spindle driving device is connected to each phase winding in parallel at a low speed to make a Y connection, and at a high speed to a Δ connection by connecting in series. The torque and rotational speed of the motor are changed by changing the number of poles. As a result, the possible range of torque and rotational speed of the main shaft directly connected to the electric motor can be switched in two steps.

For example, as shown in Patent Document 2, the latter gear switching type main shaft drive device has gears attached to each of the main shaft and the drive shaft of the motor, and the number of teeth is between the main shaft and the drive shaft of the motor. An intermediate shaft to which two different intermediate gears are attached is provided. Then, by moving this intermediate shaft in the axial direction, any of the intermediate gears meshes with the main shaft and the drive shaft of the electric motor, so that the range of the main shaft torque and rotational speed can be taken in two stages according to the gear ratio. Can be switched.
JP-A-6-296350 JP 2001-322044 A

By the way, when difficult-to-cut materials such as titanium and inconel used for aircraft are to be cut, a very large torque corresponding to the improvement in tool performance is required for the spindle of the machining center.
However, in the above-mentioned main shaft drive device of the coil switching method, since the torque and the rotational speed can be switched only in two stages, the range of the torque is narrow and a desired torque suitable for cutting difficult-to-cut materials. There was a problem that could not get.

  Further, in the case of a gear switching type spindle drive device, the range that can be taken by the torque and the rotational speed can be expanded by providing a plurality of intermediate shafts and a multi-stage switching method, thereby obtaining a high torque. It can also be considered possible. In this case, however, the existence of a plurality of intermediate shafts makes the spindle drive device itself large, and there is a problem that not only the configuration becomes complicated but also the weight increases.

  Furthermore, in the above spindle switching device of the winding switching system and the gear switching system, the output temporarily decreases due to a decrease in the rotational speed and torque when switching the winding system and the gear, respectively. There was a problem that it was not possible to perform a proper switching.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and is intended for spindle driving of a machine tool capable of expanding the range of torque and rotational speed by enabling multi-stage switching while reducing the weight and compactness of the apparatus itself. An object is to provide an apparatus.
It is another object of the present invention to provide a spindle driving device for a machine tool that can prevent a torque and a rotational speed from being temporarily reduced at the time of switching and can perform a smooth switching while keeping the output constant.

の関係が成立することを特徴とする。 In order to solve the above problems, the present invention proposes the following means.
That is, the spindle driving device for a machine tool according to the present invention is the above-described three-axis spindle driving device for a machine tool that transmits the rotation of the driving shaft of the three-phase induction motor to the spindle of the machine tool and rotationally drives the spindle. In the phase induction motor, the winding method of the three-phase winding on the stator side is a Y-connection, a low-speed winding that rotates the drive shaft at a low speed, and a Δ-connection, a high-speed winding that rotates the drive shaft at a high speed. The drive shaft is integrally provided with the drive shaft on the outer peripheral surface of the drive shaft, and the large-diameter main shaft gear and the small-diameter main shaft gear are mutually connected to the main shaft on the outer peripheral surface of the main shaft. An axial shaft is provided integrally with the main shaft, an intermediate shaft is disposed between the drive shaft and the main shaft, and a small-diameter intermediate gear and a large-diameter intermediate gear are mutually attached to the outer peripheral surface of the intermediate shaft. It is integrally provided adjacent to the axial direction of the intermediate shaft. The intermediate shaft engages the large-diameter intermediate gear with the drive gear and the small-diameter intermediate gear meshes with the large-diameter main shaft gear, and the large-diameter intermediate gear is both the drive gear and the small-diameter main shaft gear. A first stage in which the combination of the winding method of the three-phase winding and the position of the intermediate shaft is a low-speed winding-low-speed position, and a high-speed winding-low-speed position. The rotation speed of the spindle increases as the second stage, the third stage with the low-speed winding—the high-speed position, and the fourth stage with the high-speed winding—the high-speed position are sequentially switched. The rotation speed at the boundary where the output becomes constant when the rotation speed is increased is defined as the base rotation speed, and the rotation at the boundary where the output starts decreasing when the rotation speed is further increased than the base rotation speed. The speed is defined as the output reduction speed, the base rotation speed at the low-speed winding of the three-phase induction motor is N ₀ , the output reduction speed is N ₁ , the base rotation speed at the high-speed winding is N ₂ , and the output The reduction speed is N ₃ , the number of teeth of the large diameter intermediate gear is Z ₁ , the number of teeth of the small diameter intermediate gear is Z ₂ , the number of teeth of the large diameter main shaft gear is Z ₃ , and the number of teeth of the small diameter main shaft gear is the number upon a Z _4,

The relationship is established .

  According to the spindle driving device of the machine tool having such characteristics, the three-phase winding on the stator side of the three-phase induction motor is in two stages of a low-speed winding having a Y connection and a high-speed winding having a Δ connection. In addition to being able to switch, it is possible to switch in two steps according to the gear ratio by sliding the intermediate shaft between the low speed position and the high speed position. Speed switching can be performed. Thereby, it is possible to expand the range that the torque and the rotation speed can take.

In addition, the torque and rotational speed of the spindle fluctuate when switching from the first stage to the second stage, when switching from the second stage to the third stage, and when switching from the third stage to the fourth stage. Absent. Thereby, the output of the electric motor can be maintained at the time of switching, and smooth switching can be performed.

According to the spindle driving device for a machine tool according to the present invention, a structure using both the coil switching method and the gear switching method enables four-stage switching without providing a plurality of intermediate shafts, and thus is lightweight and compact. It is possible to expand the possible range of torque and rotational speed while achieving the above.
Further, since the torque and the rotational speed of the main shaft do not fluctuate at the time of switching, it is possible to perform smooth switching while maintaining the output of the electric motor.

Hereinafter, a spindle drive device for a machine tool according to an embodiment of the present invention will be described in detail with reference to the drawings. FIG. 1 is a side sectional view showing an outline of a spindle driving device according to an embodiment.
As shown in FIG. 1, the spindle drive device 1 includes a spindle unit 10, an electric motor unit 20, and an intermediate shaft unit 40 that are independently arranged in the housing 2 with their respective axes O, P, and Q being parallel to each other. Thus, the rotation of the electric motor unit 20 is transmitted to the main spindle unit 10 via the intermediate shaft unit 40.

  The main shaft unit 10 includes a main shaft 11 having a substantially cylindrical shape extending along the axis O, and the main shaft 11 is formed by a plurality of bearings 12 provided in the housing 2 at the front end side (left side in FIG. 1) and the rear end. The side (the right side in FIG. 1) is pivotally supported and is rotatable around the axis O.

A tapered hole 13 having a tapered shape that gradually increases in diameter toward the distal end side is opened along the axis O at the distal end of the main shaft 11. A tool (not shown) is taper fitted into the taper hole 13.
In addition, a through hole 14 that penetrates the main shaft 11 along the axis O is formed in the main shaft 11 so as to be continuous with the tapered hole 13. A slide shaft 15 slidable along the axis O is inserted into the through hole 14. A piston rod 17 of an unclamp cylinder 16 for releasing the tool is inserted at the rear end of the slide shaft 15. Are connected. As a result, the slide shaft 15 slides toward the distal end side when the piston rod 17 of the unclamp cylinder 16 is actuated.

  A clamp claw 15 a is provided at the tip of the slide shaft 15, and the tool can be firmly attached to the main shaft 11 by sandwiching the tool fitted in the tapered hole 13. . Further, when the slide shaft 15 slides toward the distal end side, the clamp claws 15a and 15a are opened so that the tool is released and simultaneously pushed out from the tapered hole 13 of the main shaft 11.

On the other hand, a large-diameter main shaft gear 18 is integrally attached to the main shaft 11 at a position slightly on the rear end side from the center in the axis O direction on the outer peripheral surface of the main shaft 11.
Further, a small diameter main shaft gear 19 having a smaller diameter than the large diameter main shaft gear 18 is integrally attached to the rear end side of the large diameter main shaft gear 18 on the outer peripheral surface of the main shaft 11. The small-diameter spindle gear 19 is disposed at predetermined intervals in the axis O direction to the large径主shaft gear 18, the number of teeth Z ₄ of the gear teeth 19a of the small-diameter spindle gear 19 gear teeth of the large径主shaft gear 18 It is set smaller than the number of teeth _{Z 3} of 18a.

  The motor unit 20 is connected to a three-phase induction motor 21 and a rotor (not shown) in the three-phase induction motor 21, extends toward the tip side along the axis P, and is rotatable about the axis P. And a drive shaft 22.

A drive shaft gear 24 having gear teeth 24 a having the number of teeth Z ₀ is integrally attached to the outer periphery of the front end of the drive shaft 22, and the front end side and the rear end side of the drive shaft gear 24 are bearings in the housing 2. 25 and 25 are pivotally supported. Thereby, when the drive shaft 22 rotates, the drive shaft gear 24 also rotates around the axis P integrally.

  Next, the winding method of the three-phase winding 30 on the stator (not shown) side provided in the three-phase induction motor 21 of the motor unit 20 will be described with reference to FIGS. 2A is a schematic diagram of a three-phase winding having a Y connection, FIG. 2B is a schematic diagram of a three-phase winding having a Δ connection, and FIG. 3 is a schematic diagram of a winding type switching circuit. It is.

The three-phase winding 30 has three winding groups, a first layer winding group Ph1, a second layer winding group Ph2, and a third layer winding group Ph3.
First Somaki line group Ph1 coil C1, C2, C3, together with the C4 are connected in series in this order, the coils C2 and terminals _{U 1} is provided between the C3, the ends of the coil C4 side terminal U ₂ is provided.
The second Somaki line group Ph2 are together with the coil C5, C6, C7, C8 are connected in series in this order, the terminal _{V 1} is provided between the coils C6 and C7, the coils C8 side terminal V ₂ is provided at the end.
Similarly, the third phase winding groups Ph3 are together with the coil C9, C10, C11, C12 are connected in series in this order, the terminal _{W 1} is provided between the coil C10 and C11, the coil C12 terminal W ₂ is provided on the end side.

  The end of the coil C4 of the first phase winding group Ph1 is connected to the end of the second phase winding group Ph2 on the coil C5 side, and the end of the second phase winding group Ph2 on the coil C8 side is The end of the third phase winding group Ph3 on the coil C9 side is connected, and the end of the third phase winding group Ph3 on the coil C12 side is connected to the end of the first phase winding group Ph1 on the coil C1 side. Yes. Thereby, the closed circuit where the coils C1-C12 were connected in series is comprised.

When the Y-connection shown in FIG. 2 (a) is used for the three-phase winding 30, the electromagnetic switch MCC1 is turned on and the electromagnetic switch MCC2 is turned off in the switching circuit shown in FIG. Thereby, three-phase power of U-phase, V-phase, and W-phase is supplied from the three-phase AC power supply 50 to the terminals U ₁ , V ₁ , and W ₁ , respectively, and the terminals U ₂ and V ₂ in the three-phase winding 30 are respectively supplied. , U ₂ are connected to each other to form a neutral point, and a Y-connected three-phase winding 30 is formed.

On the other hand, when the three-phase winding 30 has the Δ connection shown in FIG. 2B, the electromagnetic switch MCC1 is turned off and the electromagnetic switch MCC2 is turned on in the switching circuit shown in FIG. Thereby, a three-phase winding 30 of Δ connection is configured in which three-phase power of U-phase, V-phase, and W-phase is supplied from the three-phase AC power supply 50 to the terminals U2, V2, and W2, respectively.
FIG. 3 shows a state in which the electromagnetic switch MCC1 is off and the electromagnetic switch MCC2 is on.

The number of poles in the case of Y connection as described above is eight, and the number of poles in the case of Δ connection is four. Since the rotation speed of the three-induction motor 20 is inversely proportional to the number of poles, the drive shaft 22 rotates at a low speed by setting the three-phase winding 30 to the Y connection, and the drive shaft 22 rotates at a high speed by setting the Δ connection. .
That is, in the induction motor 20 of this embodiment, the driving shaft of the three-phase winding 30 on the stator side is switched between the low-speed winding that is Y-connected and the high-speed winding that is Δ-connected. The possible range of 20 torques and rotation speeds can be switched in two steps.

As shown in FIG. 1, the intermediate shaft unit 40 is disposed between the main shaft unit 10 and the electric motor unit 20, and includes an intermediate shaft 41, an intermediate gear portion 42, and a cylinder portion 43.
The intermediate shaft 41 is a cylindrical member extending along an axis Q parallel to the axis O and the axis P, and is installed in the housing 2 so as to be movable along the direction of the axis Q. The intermediate gear portion 42 is integrally attached to the outer peripheral surface of the intermediate shaft 41, and the intermediate gear portion 42 is configured to rotate around the intermediate shaft 41 via an intermediate shaft bearing 46. .

The intermediate gear portion 42 is configured by integrating a large-diameter intermediate gear 44 and a small-diameter intermediate gear 45 having different outer diameters so as to be adjacent to each other in the axis Q direction. Also, the gear teeth Z ₂ of teeth 45a is set smaller than the number of teeth Z ₁ of the gear teeth 44a of the large-diameter intermediate gear 44, the small-diameter intermediate gear 45 toward the large-diameter intermediate gear 44 of the small-diameter intermediate gear 45 It is arrange | positioned rather than the rear end side.

  The cylinder portion 43 includes a rod 43a connected to the rear end of the intermediate shaft 41. The rod 43a moves forward and backward to slide the intermediate shaft 41 along the axis Q. Yes.

Here, when the rod 43a moves forward (in the state shown in FIG. 1), the intermediate shaft 41 is moved to the position shown in FIG. 1, that is, the gear teeth 44a of the large-diameter intermediate gear 44 are changed to the gear teeth 24a of the drive shaft gear 24. At the same time, the small-diameter intermediate gear 45 is placed at a low speed position where it meshes with the large-diameter main shaft gear 18. At this time, the gear ratio of the main shaft 11 to the drive shaft 22 is (Z ₀ / Z ₁ ) × (Z ₂ / Z ₃ ).
On the other hand, when the rod 43a is retracted, the intermediate shaft 41 moves to the rear end side as shown by the arrow in FIG. 1, and the gear teeth 44a of the large-diameter intermediate gear 44 are connected to the gear teeth 24a of the drive gear 24 and the small-diameter. It is placed at a high speed position that meshes with the gear teeth 19 a of the main shaft gear 19. In this case, the gear ratio of the main shaft 11 to the drive shaft 22 is (Z ₀ / Z ₁ ) × (Z ₁ / Z ₄ ).

Here, since Z ₃ > Z ₄ , the gear ratio is smaller when placed at the high speed position than when placed at the low speed position. Accordingly, when the intermediate shaft 41 is placed at the low speed position, the rotational speed of the main shaft 11 decreases and the torque increases. When the intermediate shaft 41 is placed at the high speed position, the rotational speed of the main shaft 11 increases and the torque increases. Will become smaller. That is, in the spindle drive device 1 of the present embodiment, the range of the rotational speed and the torque can be switched in two steps by moving the position of the intermediate shaft 41 between the low speed position and the high speed position. is there.

According to the spindle drive device 1 having the above-described configuration, the stator unit of the motor unit 20 has a three-phase winding 30 with a Y-connection and a high-speed winding with a Δ connection in two stages. Since switching is possible and the intermediate shaft 41 can be switched in two stages, a low speed position and a high speed position, by combining these, the range that the rotational speed and the torque can take can be switched in a total of four stages. .
As a result, for example, as shown in FIG. 4, the combination of the winding method of the three-phase winding 30 and the position of the intermediate shaft 41 is the first stage in which the low speed winding-low speed position is set, and the high speed winding-low speed position. The rotation speed of the spindle unit 10 increases and the torque decreases as the second stage, the third stage in the low speed winding-high speed position, and the fourth stage in the high speed winding-high speed position are sequentially switched. can do.
That is, according to the spindle drive device 1 of the present embodiment, by using a configuration in which the winding switching method and the gear switching method are used together, four-stage switching can be performed without providing a plurality of intermediate shaft units 40. This makes it possible to easily cut a difficult-to-cut material by expanding the range of torque and rotational speed while achieving lightweight and compact.

  Further, in the spindle drive device 1 of the present embodiment, at the time of switching from the first stage to the second stage, at the time of switching from the second stage to the third stage, and at the time of switching from the third stage to the fourth stage. Switching of the rotation speed and torque of the main shaft 11 in each of them can be suppressed, and switching can be performed while the output of the electric motor is in position. Hereinafter, this point will be described.

FIG. 5A shows the relationship between the rotational speed and output of the three-phase induction motor 21 during operation when the three-phase winding 30 is a low-speed winding (Y connection).
As the rotational speed increases from 0, the output also increases. When the rotational speed becomes higher than N ₀ , the output becomes constant, and when the rotational speed becomes higher than N ₁ , the output starts to decrease. That is, at the time of the low-speed winding of the three-phase induction motor 30, stable operation with the maximum output can be performed in the range of the rotation speed from N _{0 to} N ₁ (low-speed winding stable region). N ₀ is defined as a low-speed winding base rotation speed, and N ₁ is defined as a low-speed winding output reduction speed.

FIG. 5B shows the relationship between the rotational speed and output of the three-phase induction motor 21 during operation when the three-phase winding 30 is a high-speed winding (Δ connection).
As in FIG. 5A, the output increases as the rotational speed increases from 0. When the rotational speed becomes greater than N ₂ , the output is constant and the rotational speed is greater than N _3. Then the output begins to drop. That is, at the time of high-speed winding of the three-phase induction motor 30, stable operation with the maximum output can be performed in the range of the rotation speed from N _{2 to} N ₃ (high-speed winding stable region). N ₂ is defined as the high-speed winding base rotation speed, and N ₃ is defined as the high-speed winding output reduction speed.

Based on the above, by finding a condition that the rotational speed and torque of the main shaft 11 do not vary at the time of switching, the position of the output at the time of switching can be achieved.
Since the torque value is uniquely determined when the rotational speed value is determined, the above condition is obtained by paying attention only to the rotational speed.

As shown in FIG. 4, the switching from the first stage to the second stage is to switch the three-phase winding 30 from the low-speed winding (Y connection) to the high-speed winding (Δ connection).
Therefore, in order to shift from the low speed winding stable region in the first stage smoothly at a high speed winding stable region of the second stage, the main shaft 11 in the slow winding output decreasing speed N ₁ shown in FIGS. 5 (a) and rotational speed, it is sufficient to match the rotational speed of the spindle 11 in the high-speed winding base rotational speed N ₂ shown in Figure 5 (b). Note that the gear ratio does not change in switching from the first stage to the second stage.
Therefore, in order to smoothly switch from the first stage to the second stage, it is a condition that the relationship of the following expression (1) is satisfied (point A in FIG. 6).

Further, switching from the second stage to the third stage switches the three-phase winding 30 from the high speed winding (Δ connection) to the low speed winding (Y connection) and switches the intermediate shaft 41 from the low speed position to the high speed position. Is.
In this case, in order to shift from the high-speed winding stable region in the second stage to the low-speed winding stable region in the third stage while maintaining the rotational speed of the main shaft, the high-speed winding is taken into consideration in consideration of the gear ratio variation. It is only necessary that the rotational speed of the main shaft 11 at the output decrease speed N ₃ and the rotational speed of the main shaft 11 at the low-speed winding base rotational speed N ₀ coincide.

となる。
一方、三相誘導電動機３０の回転速度が低速巻線基底回転速度Ｎ_０の際の主軸１１の回転速度はの値は、

となる。 Here, the value of the rotational speed of the main shaft 11 when the rotational speed of the three-phase induction motor 30 is the high-speed winding output reduction speed N ₃ is:

It becomes.
On the other hand, when the rotation speed of the three-phase induction motor 30 is the low-speed winding base rotation speed N ₀ , the value of the rotation speed of the spindle 11 is

It becomes.

Therefore, in order to smoothly switch from the second stage to the third stage, the above two values need to coincide with each other, and as a result, the condition of the following equation (2) is satisfied (FIG. 6). B point).

  The switching from the third stage to the fourth stage is to switch the three-phase winding 30 from the low speed winding (Y connection) to the high speed winding (Δ connection). By satisfying, it is possible to smoothly switch from the third stage to the fourth stage (point C in FIG. 6).

Therefore, in the spindle drive device 1 in the present embodiment, by setting each parameter (N _{0 to} N ₃ , Z _{1 to} Z ₄ ) so as to satisfy the relationship of the above expressions (1) and (2), It is possible to eliminate fluctuations in the rotational speed and torque of the spindle 11 when switching from the first stage to the second stage, switching from the second stage to the third stage, and switching from the third stage to the fourth stage. . As a result, as shown in FIG. 6, the output of the spindle 11 at the switching points A, B, and C at the time of switching at each stage can be made constant, and smooth switching is performed without reducing the output. Is possible.

  As described above, according to the spindle drive device 1 of the present embodiment, by using a configuration in which the winding switching method and the gear switching method are used together, it is possible to perform multi-stage switching without providing a plurality of intermediate shafts 40. It is possible to expand the range of torque and rotational speed while achieving the above. In addition, by making the torque and the rotation speed at the same time the switching at each stage, the switching can be performed smoothly, and an operation that maximizes the output of the motor can be performed.

  As mentioned above, although embodiment of the spindle drive device 1 which is this invention was described in detail, unless it deviates from the technical idea of this invention, it is not limited to these, A some design change etc. are possible.

It is a sectional side view which shows the outline of the spindle drive device which concerns on embodiment. (A) is a schematic diagram of a three-phase winding having a Y connection, and (b) is a schematic diagram of a three-phase winding having a Δ connection. It is the schematic of the switching circuit of a winding system. It is a figure explaining the response | compatibility with the combination of the winding system of a three-phase winding, the position of an intermediate shaft main body, and each step. (A) is a figure which shows the relationship between the rotational speed and output of a three-phase induction motor at the time of operation when a three-phase winding is a low-speed winding (Y connection), and (b) is a high-speed winding of the three-phase winding. It is a figure which shows the relationship between the rotational speed of a three-phase induction motor at the time of the driving | operation at the time of setting it as a line ((DELTA) connection), and an output. It is a figure which shows the relationship between the rotational speed of a main axis | shaft in case a parameter is set so that an output can be maintained at the time of switching, and a torque.

Explanation of symbols

1 Spindle Drive 10 Spindle Unit 11 Spindle 18 Large Diameter Spindle Gear 18a Gear Teeth 19 Small Diameter Spindle Gear 19a Gear Teeth 20 Motor Unit 21 Three Phase Induction Motor 22 Drive Shaft 24 Drive Shaft Gear 24a Gear Teeth 30 Three Phase Winding 40 Intermediate Unit 41 Intermediate shaft 42 Intermediate gear portion 44 Large diameter intermediate gear 44a Gear teeth 45 Small diameter intermediate gear 45a Gear teeth O Axis line P Axis line Q Axis line

Claims (1)

In the spindle driving device of a machine tool that transmits the rotation of the drive shaft of the three-phase induction motor to the spindle of the machine tool and rotationally drives the spindle.
In the three-phase induction motor, the winding method of the three-phase winding on the stator side is a Y-connection and a low-speed winding that rotates the drive shaft at a low speed, and a Δ-connection that rotates the drive shaft at a high speed. It can be switched with high-speed winding,
A drive gear is provided integrally with the drive shaft on the outer peripheral surface of the drive shaft,
A large-diameter main shaft gear and a small-diameter main shaft gear are provided integrally with the main shaft at an interval in the axial direction of the main shaft on the outer peripheral surface of the main shaft,
An intermediate shaft is disposed between the drive shaft and the main shaft, and a small-diameter intermediate gear and a large-diameter intermediate gear are integrally provided adjacent to each other in the axial direction of the intermediate shaft on the outer peripheral surface of the intermediate shaft. ,
The intermediate shaft engages the large diameter intermediate gear with the drive gear and the small diameter intermediate gear meshes with the large diameter main shaft gear; and the large diameter intermediate gear is connected to the drive gear and the small diameter main shaft gear. It is possible to switch to a high-speed position that meshes with both ,
The combination of the winding method of the three-phase winding and the position of the intermediate shaft is a first stage with a low speed winding-low speed position, a second stage with a high speed winding-low speed position, a low speed winding-high speed position, The third stage, the high-speed winding-the fourth stage as a high-speed position, and the rotational speed of the main shaft is increased with the sequential switching,
The rotation speed at the boundary where the output is constant when the rotation speed is increased is defined as the base rotation speed, and the rotation speed at the boundary where the output starts to decrease when the rotation speed is further increased than the base rotation speed. Is defined as the output decrease rate,
The base rotational speed at the time of low-speed winding of the three-phase induction motor is N ₀ , the output reduction speed is N ₁ , the base rotational speed at the time of high-speed winding is N ₂ , and the output reduction speed is N ₃ , the large-diameter intermediate Z ₁ the number of teeth of the _gear, the number of teeth of the small-diameter intermediate gear Z _2, the number of teeth of the large径主shaft gear Z _3, the number of teeth of the small-diameter spindle gear upon a Z _4,

A spindle drive device for a machine tool, characterized in that

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