JP2000343379A - Spindle head controller - Google Patents

Abstract

(57) Abstract: A control device for controlling the operation of a spindle head using a magnetic bearing, the control device being capable of rotating the spindle in a region where the spindle head does not resonate. The control device includes a bearing control means for controlling the operation of a thrust magnetic bearing and a radial magnetic bearing, and a spindle motor control means for controlling the operation of a spindle motor. The tool weight estimating means 6 for estimating the weight of the tool mounted on the main shaft based on the current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing from 5, 12 and, based on the estimated tool weight,
A limit rotation speed determining means for determining a limit rotation speed of the main shaft; To prevent the spindle speed from exceeding the limit speed,
The operation of the spindle motor is controlled by the spindle motor control means 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a control device for controlling the operation of a spindle head whose spindle is rotatably supported by a magnetic bearing.

[0002]

2. Description of the Related Art FIG. 3 shows an example of a spindle head provided with the above-mentioned magnetic bearing. The illustrated spindle head 101 is provided in a vertical machining center, and has a spindle 102 whose axial direction is oriented vertically, and a rear radial magnetic bearing that supports the rear side (upper side) of the spindle 102 in the radial direction. 110 and a front radial magnetic bearing 120 that also supports the front side (lower side) of the main shaft 102 in the radial direction.
A thrust magnetic bearing 130 between the rear radial magnetic bearing 110 and the front radial magnetic bearing 120 for supporting the main shaft 102 in the axial direction; a rear angular ball bearing 107 provided on the rear side of the rear radial magnetic bearing 110; It includes a front angular ball bearing 104 provided on the front side of a front radial magnetic bearing 120, and a nut 108 screwed to the rear end of the main shaft 102. Although not shown, a tapered receiving portion for receiving the tapered portion of the tool T is formed at the front end of the main shaft 102.
By inserting the tapered part of the tool T into this receiving part,
The tool T is mounted on the main shaft 102.

Also, between the rear radial magnetic bearing 110 and the rear angular ball bearing 107, four sensors 116 for detecting the position of the main shaft 102 in the radial direction are provided on the same plane in the radial direction, and the front radial magnetic bearing is provided. 120, four sensors 125 which are also provided in the same radial plane and which detect the position of the main shaft 102 in the radial direction, and which detect the position of the main shaft 102 in the axial direction. Sensors 139 are provided.

In FIG. 1, reference numeral 103 denotes a drive rotor, which constitutes a part of a built-in type spindle motor for rotating the spindle 102 about its axis. In addition, the stator (not shown) of the spindle motor and the spindle head 10
Each of the components 1 is supported by a housing (not shown).

The rear radial magnetic bearing 110 includes a rotor 114 formed by laminating a ring-shaped metal plate, a holding member 115 for holding the rotor 114, a laminated body 112 formed by laminating the metal plates, and This laminate 11
Four stators 11 each including a coil 113 wound around 2
The inner diameter of the holding member 115 is externally fitted to and fixed to the main shaft 102, and the stator 111 is held by the housing (not shown). Further, the four stators 111 are evenly arranged along the outer peripheral surface of the rotor 114,
Similarly, the sensors 116 are equally arranged along the outer peripheral surface of the main shaft 102 in correspondence with the stator 111.

Further, the front radial magnetic bearing 120
Is a rotor 124 formed by stacking ring-shaped metal plates.
And a stator 122 composed of a laminated body 122 formed by laminating metal plates and four coils 123 wound around the laminated body 122. The inner diameter of the rotor 124 is The stator 121 is externally fitted to and fixed to the main shaft 102, and the stator 121 is held by the housing (not shown). The four stators 12
1 are evenly arranged along the outer peripheral surface of the rotor 124, and the four sensors 125 are similarly disposed on the main shaft 1
Along the outer peripheral surface 02, they are evenly arranged in correspondence with the stator 121. The main shaft 102
Are formed with two flange portions 105 and 106. The outer peripheral surface of the flange portion 106 is detected by the sensor 125, and the lower end surface thereof is detected by the sensor 139. In addition, the rotor 124
The front side is locked by the flange 105.

[0007] The thrust magnetic bearing 130 has a rotor 131 whose inner diameter is externally fitted and fixed to the main shaft 102.
And a rear stator 132 including a coil 133 formed in a ring shape and a holding ring 134 for holding the coil 133, and a coil 136 formed in a ring shape.
And a front stator 135 comprising a holding ring 137 for holding the coil 136;
2, a spacer 138 provided between the front stators 135. The outer peripheral portion of the rotor 131 has a flange 13
The flange portion 131a is located between the rear stator 132 and the front stator 135.

The spindle head 101 having the above configuration is
Its operation is controlled by a control device including a bearing control means 140 and a spindle motor control means (not shown) provided in a numerical control device (not shown). Bearing control means 1
Numeral 40 supplies predetermined power to the coils 113, 123, 133, and 136 of the rear radial magnetic bearing 110, the front radial magnetic bearing 120, and the thrust magnetic bearing 130, respectively.
The current supplied to the coils 113, 123, 133, and 136 is adjusted according to the displacement of the main shaft 102 detected by 39. On the other hand, the spindle motor control means (not shown)
A predetermined electric power is supplied to and driven by a stator (not shown) of the spindle motor, and is output from an NC program execution processing unit (NC system unit) in the numerical controller (not shown). The current supplied to the stator (not shown) is adjusted according to a rotation command (rotation direction and rotation speed) of the main shaft 102.

When predetermined power is supplied to the coils 113, 123, 133 and 136 from the bearing control means 140, the stator 111 of the rear radial magnetic bearing 110, the stator 121 of the front radial magnetic bearing 120, and the thrust magnetic bearing The rear stator 132 and the front stator 135 of the 130 each become an electromagnet, whereby the rotors 114, 124, 131 are each attracted.

In the rear radial magnetic bearing 110,
The suction force in four directions by the four stators 111 causes the rotor 1
Similarly, in the front radial magnetic bearing 120, similarly, the attraction force in four directions by the four stators 121 acts on the rotor 124, and these rear radial magnetic bearings 1.
The main shaft 102 is supported in the radial direction by the radial magnetic bearing 120 and the front radial magnetic bearing 120.

As described above, the radial position of the main shaft 102 is detected by the sensors 116 and 125, and the main shaft 102 is displaced from the neutral position between the stators 111 and the neutral position between the stators 121. If the position is shifted from the position, the position
6 and the sensor 125, and the power supplied to each of the stators 111 and 121 is adjusted by the bearing control means 140 based on the detection signals. That is, each stator 111 and rotor 114
And the distance between each of the stators 121 and the rotor 124, the power supplied to the stator 111 and the stator 121 whose distance is wider than the reference distance is increased, and the attraction force is increased. The power supplied to the stators 111 and 121 whose intervals are narrower than the reference intervals is reduced, and the suction force is reduced. As described above, the spindle 10
2 is always between the stators 111 and the stator 121
It is controlled to be located at a neutral position between the two.

Further, in the thrust magnetic bearing 130, the flange 131a of the rotor 131 is moved forward and backward (up and down) by the rear stator 132 and the front stator 135.
The main shaft 102 is supported in the axial direction such that the main shaft 102 is located at an intermediate position between the rear stator 132 and the front stator 135.

As described above, the axial position of the main shaft 102 is detected by the sensor 139, and if the main shaft 102 is displaced from the intermediate position between the rear stator 132 and the front stator 135, the positional deviation is detected. Sensor 1
The power supplied to the rear stator 132 and the front stator 135 is adjusted by the bearing control means 140 based on the detection signal. That is, the flange portion 1 of the rear stator 132 and the rotor 131
In the space between the front stator 135 and the front stator 135 or the space between the front stator 135 and the flange portion 131a, the power is increased for the rear stator 132 or the front stator 135 in which the space is wider than the reference space. While the suction force is increased, the power supplied to the rear stator 132 or the front stator 135 whose interval is narrower than the reference interval is reduced, the suction force is reduced, and the rotor 131 is The main shaft 102 is controlled to be always located at an intermediate position between the rear stator 132 and the front stator 135, and the main shaft 102 is supported in the axial direction.

Thus, according to the spindle head 101, the spindle head 101 can be supported in the radial and axial directions by the attractive force of the electromagnet without directly contacting the spindle 102. 10
2 can be properly supported.

[0015]

When the spindle is rotated, the spindle head vibrates at a frequency substantially equal to the number of revolutions. When the frequency of the spindle head approaches the natural frequency of the spindle head, The spindle head resonates and eventually breaks down. In the case of a spindle head in which the spindle is supported by rolling bearings, the limiting speed is determined by the performance of the rolling bearing, and the limiting speed of the rolling bearing is considerably lower than the natural frequency of the spindle head. Is unlikely to cause such a problem. However, in the case of a spindle head in which the spindle is supported by a magnetic bearing, the spindle is supported in a non-contact manner, so that the rotation speed of the spindle is not limited by the performance of the magnetic bearing. Since the rotation speed of the main shaft can be increased to near the frequency, a problem due to such resonance occurs.

The natural frequency of the spindle head using the magnetic bearing is easily affected by the weight of the tool to be mounted because the size of the spindle head is relatively small and lightweight. Fluctuates greatly depending on the weight of Specifically, the heavier the weight of the tool to be mounted, the lower the natural frequency of the spindle head. Therefore,
In the case of a spindle head using a magnetic bearing, if the weight of the tool to be mounted is heavy, it is easy for the natural frequency to be equal to or lower than the number of rotations of the tool,
This causes the above-mentioned resonance problem.

The present invention has been made in view of the above circumstances, and is a control device for controlling the operation of a spindle head using a magnetic bearing, wherein the control device can rotate the spindle in a region where the spindle head does not resonate. The purpose is to provide the device.

[0018]

According to the first aspect of the present invention, there is provided a spindle, and a thrust magnetic bearing and a radial magnetic bearing rotatably supporting the spindle. A device for controlling the operation of a spindle head including a housing for holding the thrust magnetic bearing and the radial magnetic bearing, and a spindle motor for driving the spindle to rotate about the spindle. Bearing control means for controlling operation;
A spindle motor control means for controlling the operation of the spindle motor, wherein the control means is mounted on the spindle based on a current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing from the bearing control means. Tool weight estimating means for estimating the weight of the tool, and limit speed determining means for determining a limit speed of the spindle based on the tool weight estimated by the tool weight estimating means, The spindle motor control means is configured to control the operation of the spindle motor based on the limit rotation speed determined by the limit rotation speed determination means so that the rotation speed of the spindle does not exceed the limit rotation speed. It is characterized by having done.

When a tool is mounted on the spindle, if the spindle head is mounted on a horizontal machine tool, a radial load acts on the spindle due to the weight of the tool. When the spindle head is mounted on a vertical machine tool, the current supplied from the bearing control means to the radial magnetic bearings increases compared to when the tool is not mounted. Therefore, in order to maintain the neutral position, the current supplied from the bearing control means to the thrust magnetic bearing increases as compared to when the tool is not mounted. When the spindle head is provided obliquely, loads in the radial and axial directions are applied to the spindle by the weight of the tool, so that the current supplied from the bearing control means to the radial magnetic bearing and the thrust magnetic bearing is reduced. It increases compared to when no tools are installed.

The current value supplied to the radial magnetic bearing and the thrust magnetic bearing changes according to the load acting on the main shaft, that is, the tool weight, and by measuring the current value according to the tool weight in advance. , The relationship between the tool weight and the current value can be known, and a relational expression for these can be obtained. The tool weight estimating means is, for example, based on the relational expression thus obtained, based on the actual current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing from the bearing control means, and in fact, Estimate the weight of the installed tool.

As described above, when the spindle is rotated, the spindle head vibrates at a frequency substantially equal to the number of revolutions,
When this frequency approaches the natural frequency of the spindle head, the spindle head resonates. Therefore, a value obtained by multiplying the natural frequency of the spindle head by a predetermined safety factor (for example, 0.9) is defined as the critical rotation speed of the spindle. You can see. On the other hand, a spindle head using a magnetic bearing is relatively small in size and light in weight, so that its natural frequency is easily affected by the weight of a tool to be mounted. The value changes. Therefore, by measuring the natural frequency of the spindle head according to the tool weight in advance, the tool weight and the limit rotational speed (=
The relationship with the natural frequency × 60 × safety factor (rpm)) can be known, and a relational expression for these can be obtained. The limit rotational speed determining means calculates, for example, the limit rotational speed of the spindle based on the tool weight estimated by the tool weight estimating means on the basis of the relational expression thus obtained, and determines the limit rotational speed. . The spindle motor control means controls the operation of the spindle motor so that the rotation speed of the spindle does not exceed the limit rotation speed determined in this way. Thereby, the vibration of the spindle head accompanying the rotation of the spindle can be set to a value smaller than its natural frequency.

As described above, according to the present invention, even if a tool having any weight is used, the main spindle on which the tool is mounted can be rotated at a lower rotational frequency than the natural frequency of the main spindle head. It is possible to reliably prevent the conventional problem that the vibration of the spindle head due to the rotation approaches the natural frequency of the spindle head and resonates and eventually breaks.

The relationship between the current value supplied to the radial magnetic bearing and / or the thrust magnetic bearing and the tool weight, and the relationship between the tool weight and the limit rotation speed are defined in claim 2.
As in the invention according to the first aspect, these actually measured values measured in advance may be stored in the data storage means as a data table. In this case, the tool weight estimating means:
The data storage means is searched based on a current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing, and the obtained tool weight value is estimated to be the weight of the tool. The rotation speed determination means is configured to search the data storage means based on the tool weight estimated by the tool weight estimation means, and determine the obtained limit rotation speed as the limit rotation speed of the spindle. .

[0024]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram illustrating a numerical control device according to the present embodiment. It should be noted that the numerical control device 1 of the present embodiment shown in FIG. 1 controls the operation of the vertical machine tool including the spindle head 101 shown in FIG.

As shown in FIG. 1, this numerical control device 1 includes an NC system unit 2, a spindle head control unit 3, a tool change operation control unit 8, and an input / output interface 9 as its main components. The NC system unit 2, the spindle head control unit 3, the tool change operation control unit 8, and the input / output interface 9 are connected to each other via a bus line 10, and the NC system unit 2, the spindle head control unit 3, and the tool The exchange operation control unit 8 is connected to an external MDI input device, a display device, a spindle motor drive amplifier 11, a bearing drive amplifier 12, and other parts of a machine tool via an input / output interface 9, respectively.

The NC system section 2 is a function section for executing, for example, a machining program and numerically controlling the operation of each section of the machine tool. The tool change operation control section 8 receives a tool change command from the NC system section 2. This is a functional part for driving and controlling a tool changer attached to a machine tool to execute tool change. In addition, the spindle head control unit 3
This is a functional part that controls the operation of the spindle head 101 via the spindle motor drive amplifier 11 and the bearing drive amplifier 12 based on an execution command output from the C system unit 2.

The spindle head control unit 3 further includes a spindle motor control unit 4, a bearing control unit 5, a tool weight estimation processing unit 6, and a limit rotation speed determination processing unit 7. The bearing control unit 5 and the bearing drive amplifier 12 correspond to the bearing control unit 140 shown in FIG. 3, and the bearing control unit 5 receives detection signals from the sensors 116, 125, and 139, and A drive command is output to the bearing drive amplifier 12 so that the motor 102 is maintained at the neutral position, and a current corresponding to the drive command is supplied from the bearing drive amplifier 12 to the rear radial magnetic bearing 110, the front radial magnetic bearing 120, and the thrust. The current is output to the magnetic bearing 130, and the electric current is applied to the rear radial magnetic bearing 110 and the front radial magnetic bearing 1.
20 and the thrust magnetic bearing 130 are driven and controlled.

The tool weight estimation processing unit 6 receives the current value supplied to the thrust magnetic bearing 130 from the bearing drive amplifier 12 and receives the current value of the tool T currently mounted on the main shaft 102.
This is a functional part for calculating the weight of the vehicle. The tool weight estimation processing unit 6 stores a relational expression between the current value and the tool weight. The tool weight estimation processing unit 6 calculates the tool T based on the relational expression and the received current value. Calculate the weight of

When the tool T is mounted on the spindle 102, since the spindle head 101 of this embodiment is provided on a vertical machine tool, a load in the axial direction acts on the spindle 102 due to the tool weight. In order to maintain the neutral position, the current supplied from the bearing drive amplifier 12 to the thrust magnetic bearing 130 increases compared to when the tool is not mounted. The current value supplied to the thrust magnetic bearing 130 changes according to the load acting on the main shaft 102, that is, the tool weight.
By measuring the current value according to the tool weight in advance, the relationship between the tool weight and the current value can be known, and a relational expression for these can be obtained. The relational expression obtained in this way is stored in the tool weight estimation processing unit 6,
As described above, the tool weight estimation processing unit 6 calculates the weight of the tool T currently mounted on the spindle 102 from the stored relational expression and the received current value.

When the spindle head 101 is mounted on a horizontal machine tool, a radial load is applied to the spindle 102 by the weight of the tool. The current supplied to the rear radial magnetic bearing 110 and the front radial magnetic bearing 120 increases as compared to when the tool is not mounted. Therefore, in this case, a relational expression between the current value supplied to the rear radial magnetic bearing 110 and the front radial magnetic bearing 120 and the tool weight is obtained in advance and stored in the tool weight estimation processing unit 6. The tool weight estimation processing unit 6 calculates the weight of the tool T from the relational expression and the current value. When the spindle head 101 is provided obliquely, loads in the radial and axial directions act on the spindle 102 due to the weight of the tool. Therefore, the rear radial magnetic bearing 110, the front radial magnetic The current supplied to the bearing 120 and the thrust magnetic bearing 130 increases as compared to when the tool is not mounted. Therefore, in this case, a relational expression between the current value supplied to the rear radial magnetic bearing 110, the front radial magnetic bearing 120, and the thrust magnetic bearing 130 and the tool weight is obtained in advance, and the relational expression is obtained. The tool weight estimation processing unit 6 calculates the weight of the tool T from the relational expression and the current value.

The limit rotation speed determination processing section 7 is a functional portion that receives the tool weight value calculated by the tool weight estimation processing section 6 and calculates the limit rotation speed of the spindle 102. The relational expression between the tool weight and the limit rotational speed is stored in the limit rotational speed determination processing unit 7. Based on the relational expression and the received tool weight value, the limit rotational speed determination processing unit 7 stores the relational expression. The limit rotation speed is calculated.

As described above, when the spindle 102 is rotated, the spindle head 101 vibrates at a frequency substantially equal to the number of revolutions, and when the frequency approaches the natural frequency of the spindle head 101, the spindle head 101 starts rotating. Because of resonance, a value obtained by multiplying the natural frequency of the spindle head 101 by a predetermined safety factor can be regarded as the limit rotation speed of the spindle 102. On the other hand, the spindle head 101 using the magnetic bearings 110, 120, 130
Is relatively small in size and light in weight, and its natural frequency is easily affected by the weight of the tool T to be mounted, and its value changes according to the weight of the tool T.
Therefore, by measuring the natural frequency of the spindle head 101 according to the tool weight in advance, the relationship between the tool weight and the limit rotational speed (= natural frequency × 60 × safety factor (rpm)) can be known. , The relational expressions for these can be obtained. The relational expression obtained in this manner is stored in the limit rotational speed determination processing unit 7, and as described above,
The limit rotation speed determination processing unit 7 calculates the limit rotation speed of the main shaft 102 based on the relational expression and the received tool weight value.
The natural frequency of the spindle head 101 can be determined, for example, by rotating the spindle 102 on which a tool T having a predetermined weight is mounted at a predetermined rotation speed, and using the acceleration pickup or the like to generate the vibration of the spindle head 101 accompanying the rotation. It can be obtained by performing frequency analysis on the detected vibration signal using an analyzer such as FFT.

The spindle motor control section 4 receives a rotation command (command relating to the rotation direction and the number of rotations) of the spindle 102 output from the NC system section 2 and sends a drive command corresponding thereto to the spindle motor drive amplifier 11. The spindle motor drive amplifier 11 which receives the drive command
Then, a corresponding current is supplied to the stator (not shown), and the spindle motor is rotated according to the rotation command. Further, the spindle motor control unit 4 receives the value of the limit rotation speed calculated by the limit rotation speed determination processing unit 7, and issues a drive command such that the rotation speed of the spindle motor does not exceed the limit rotation speed. Output to the drive amplifier 11 and
The spindle motor is rotated so that the rotation speed is equal to or lower than the limit rotation speed. That is, the spindle motor control unit 4 controls the rotation speed output from the NC system unit 2 to the limit rotation speed determination processing unit 7.
If the rotation speed is equal to or less than the limit rotation number received from the controller, a drive command corresponding to the rotation speed output from the NC system unit 2 is output to the spindle motor drive amplifier 11, and the spindle motor rotates at the rotation speed as instructed. If the rotation speed output from the NC system unit 2 exceeds the limit rotation speed received from the limit rotation speed determination processing unit 7, a drive command corresponding to the limit rotation speed is output to the spindle motor drive amplifier 11. Then, the spindle motor is rotated at this limit rotation speed.

As described above, when a tool change command is output from the NC system unit 2 and received by the tool change operation control unit 8, tool change is executed under the control of the tool change operation control unit 8. A new tool T is mounted on the spindle 102. When a new tool T is mounted on the spindle 102 in this way, the tool weight estimation processing unit 6 calculates the weight of the tool T, and then receives the tool weight value and determines the limit rotation speed determination processing. The unit 7 calculates a limit rotation speed based on the tool weight, and transmits this to the spindle motor control unit 4. Thereafter, a rotation command is output from the NC system unit 2 and received by the spindle motor control unit 4. If the command rotation speed from the NC system unit 2 is equal to or less than the limit rotation speed, the spindle motor control Under the control of the unit 4, the main shaft 102 is rotated to the commanded rotational speed, and when the commanded rotational speed exceeds the limit rotational speed, the main shaft 102 is rotated to the limit rotational speed. .

As described above, according to the spindle head control unit 3 of the present embodiment, the tool T
Can be rotated at a frequency lower than the natural frequency of the spindle head 101.
The vibration of the spindle head 101 due to the rotation of the spindle head 101 approaches the natural frequency of the spindle head 101, resonates, and eventually prevents the conventional problem such as being destroyed. . Incidentally, in the spindle motor control section 4, it is also possible to take measures such as outputting an alarm when the commanded rotational speed exceeds the limit rotational speed, but in this example, the spindle motor control portion 4 rotates at the limit rotational speed as described above. It was configured to be.

Although the embodiment of the present invention has been described above, it is needless to say that the specific embodiment of the present invention is not limited to this. For example, in the above-described example,
The weight of the tool currently mounted on the main shaft 102 is calculated from the relational expression between the current value supplied to the thrust magnetic bearing 130 and the tool weight, and the main shaft 1 is calculated from the relational expression between the tool weight and the limit rotation speed.
02, the limit rotational speed is calculated. As shown in FIG. 2, “current value supplied to thrust magnetic bearing 130” vs. actual measurement value of “tool weight”, and “tool weight” vs. “limit value of tool” Number of rotations (= actual measured value of natural frequency x 60 x safety factor)
(Rpm) is stored in the data storage unit 13 as a data table, and the tool weight estimation processing unit 6 searches the data storage unit 13 based on the current value actually supplied to the thrust magnetic bearing 130. Then, the tool weight estimation processing unit 6 is configured to estimate the obtained tool weight value as the weight of the tool currently mounted on the spindle 102, and the limit rotation speed determination processing unit 7 performs the tool weight estimation processing. Searching the data storage unit 13 based on the tool weight estimated in the unit 6;
The limit rotation speed determination processing unit 7 may be configured to determine the obtained limit rotation speed as the limit rotation speed of the main shaft 102.

In this case, also in this case, the spindle head 10
1 is mounted on a horizontal machine tool, the data storage unit 13 uses a measured value of “current value supplied to the rear radial magnetic bearing 110 and the front radial magnetic bearing 120” vs. “tool weight” as a data table as a data table. And the spindle head 1
When 01 is provided obliquely, the measured value of “the current value supplied to the rear radial magnetic bearing 110, the front radial magnetic bearing 120, and the thrust magnetic bearing 130” versus the “tool weight” is used as a data table. Data storage unit 1
3 is stored.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a numerical control device according to an embodiment of the present invention.

FIG. 2 is a block diagram showing a numerical control device according to another embodiment of the present invention.

FIG. 3 is a sectional view showing a spindle head using a magnetic bearing according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Numerical control apparatus 2 NC system part 3 Spindle head control part 4 Spindle motor control part 5 Bearing control part 6 Tool weight estimation processing part 7 Limit rotation speed determination processing part 11 Spindle motor drive amplifier 12 Bearing drive amplifier 13 Data storage part 101 Spindle Head 110 Rear radial magnetic bearing 120 Front radial magnetic bearing 130 Thrust magnetic bearing

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) F16C 32/04 F16C 32/04 A F term (Reference) 3C001 KA06 KA07 TA06 TB05 TB06 TB08 3C011 AA04 3C029 DD00 3C045 FD16 FD23 3J102 AA01 BA03 BA19 CA02 DA02 DA03 DA09 DB08 DB10 DB11 DB37 GA07

Claims (2)

[Claims] 1. A main shaft, a thrust magnetic bearing and a radial magnetic bearing rotatably supporting the main shaft, a housing for holding the thrust magnetic bearing and the radial magnetic bearing, and a main shaft motor for driving the main shaft to rotate about the main shaft. A bearing control means for controlling the operation of the thrust magnetic bearing and the radial magnetic bearing, and a spindle motor control means for controlling the operation of the spindle motor. In the control device, tool weight estimating means for estimating a weight of a tool mounted on the main shaft based on a current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing from the bearing control means; A limit speed determining means for determining a limit speed of the main spindle based on the tool weight estimated by the estimating means. In both cases, the spindle motor control means controls the operation of the spindle motor based on the limit rotation speed determined by the limit rotation speed determination means so that the rotation speed of the spindle does not exceed the limit rotation speed. A spindle head control device characterized in that: 2. A data storage means for storing, as a data table, a relationship between a current value supplied to the thrust magnetic bearing and / or the radial magnetic bearing and the tool weight, and a relationship between the tool weight and the limit rotation speed. Wherein the tool weight estimating means includes the thrust magnetic bearing and / or
Or, based on the current value supplied to the radial magnetic bearing, configured to estimate the tool weight value obtained by searching the data storage means as the weight of the tool, the limit rotation speed determination means, 2. The apparatus according to claim 1, wherein a limit rotation speed obtained by searching said data storage means is determined as a limit rotation speed of said spindle based on a tool weight estimated by said tool weight estimation means. The spindle head control device as described in the above.