JP4516889B2 - Magnetic bearing device and variable weight part replacement method for magnetic bearing device - Google Patents

Description

  The present invention relates to a magnetic bearing device, and more particularly to a magnetic bearing device that requires replacement of a variable weight portion mounted on a rotating body.

  As a conventional magnetic bearing device, when changing the tool mounted on the tip of the main shaft, the main shaft is moved to the front side in the axial direction, and the engaging member and the protective bearing are engaged with each other. There is one that restricts the movement to the front side (see, for example, Patent Document 1).

  5 and 6 show a conventional magnetic bearing device described in Patent Document 1. FIG.

  In FIG. 6, 101 is a main shaft, 102 is a front angular contact ball bearing, 103 is a rear angular contact ball bearing, 104 is a nut, 105 is a rear radial magnetic bearing, 106 is a front radial magnetic bearing, 107 is a front thrust magnetic bearing, Reference numeral 108 denotes a rear stator, 109 denotes a front stator, and 110 denotes bearing control means.

  In the conventional magnetic bearing device having the above-described configuration, in the normal state, the main shaft 101 is supported by the thrust magnetic bearing 107 in the thrust direction so as to be positioned in its neutral position. As shown in FIG. A predetermined gap t is formed between the nut 104 screwed to the rear end portion 101 and the rear angular ball bearing (protective bearing) 103. Due to the increase in the suction force of the front stator 108 described above, As shown in FIG. 5B, the main shaft 101 moves in the front side in the axial direction, that is, in the direction indicated by the arrow, and the nut 104 abuts on the rear angular ball bearing 103.

  Next, when the tool T is pulled out from the receiving portion by the operation of the tool changing means (not shown) and the new tool T is mounted on the spindle 101, the taper of the tool T is removed. Even if a load in the pulling direction is applied to the main shaft 101 due to the close contact between the portion and the receiving portion of the main shaft 101, the nut 104 and the rear angular ball bearing 103 are already in contact with and engaged with each other. There is no further movement toward the front side in the axial direction, and the load acting on the rear angular ball bearing 103 becomes a static load having a smaller value than the dynamic load.

Thereby, the collision between the nut 104 and the rear angular ball bearing 103 can be prevented, and the rear angular ball bearing 103 is prevented from being damaged.
JP 2000-176777 A

  However, in the conventional configuration, the operation of the radial magnetic bearing at the time of automatic tool change is unknown. For example, when the radial magnetic bearing is in a magnetic levitation state at the time of automatic tool change, The main shaft position fluctuates due to the load received by the main shaft from the arm, and the tool cannot be changed, or the automatic tool changing speed has to be slowed to prevent the fluctuation.

  Further, when the radial magnetic bearing is not in a magnetically levitated state at the time of automatic tool change, there is a problem that the automatic tool change cannot be performed because the position in the radial direction changes each time.

  The problem to be solved in Patent Document 1 is to prevent the protective bearing from being damaged during automatic tool change, which is different from the positioning of the spindle during automatic tool change, which is the problem of the present invention.

  The present invention solves the above-described conventional problems, and an object thereof is to provide a magnetic bearing main shaft that is highly reliable and can perform automatic tool change in a short time.

In order to achieve the above object, the present invention includes a radial magnetic bearing electromagnet that is levitated and controlled by a control current, and a rotating body that is supported by a thrust magnetic bearing electromagnet and that is controlled to rotate and stop, and is mounted on the rotating body. A mode discriminating unit for discriminating a magnetic levitation mode and a variable weight unit exchanging mode based on a variable weight unit exchanging signal applied from the outside when exchanging the variable weight unit; a magnetic levitation mode processing unit for controlling the magnetic suspension bearing of the thrust magnetic bearing electromagnet, by a signal of the mode determination unit when replacing the variable parts, and bias command generating unit for applying a bias current to the radial magnetic bearing electromagnet a bias command generating unit for applying a bias current to the thrust magnetic bearing electromagnet, the times A variable weight part replacement mode processing unit configured by a variable weight part replacement position detection unit that determines that the body has moved to a variable weight part replaceable position, and performs variable weight part replacement. .

With the above configuration, when the variable weight portion is replaced, a bias current is applied to the radial magnetic bearing electromagnet and the thrust magnetic bearing electromagnet, and the rotating body is brought into contact with the radial protection member to be positioned, thereby realizing the replacement of the variable weight portion. it can.

  As described above, according to the present invention, it is possible to provide a magnetic bearing spindle that is highly reliable and that can perform automatic tool change in a short time.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

( Reference example )
Block diagram showing the overall arrangement of FIG. 1 is a magnetic bearing device is a reference example of the present invention, cross-sectional view showing a specific example of a magnetic bearing device 2 in the present reference example, FIG. 3 is a magnetic bearing device of this reference example It is sectional drawing which shows the structure of a draw bar.

  In FIGS. 1 and 2, reference numeral 31 denotes a rotating body, 41 denotes a rotating body 31, and a variable weight unit 40 including a motor rotor 35, radial magnetic bearing rotors 33 and 34, a thrust magnetic bearing rotor 39, a tool 32, and a tool holder 37. Is the main shaft attached. The radial magnetic bearing electromagnets 22, 23, 24, 25, the thrust magnetic bearing electromagnets 26, 27, and the rotating body 31 are detected at a minute distance from the radial magnetic bearing rotors 33, 34 and the thrust magnetic bearing rotor 39. Radial displacement sensors 28 and 29 and a thrust displacement sensor 30 are arranged, and the rotating body 31 is supported in a non-contact manner at a predetermined position.

  Here, the radial magnetic bearing electromagnets 22, 23, 24, and 25 are arranged around the rotating body 31, for example, four each at a central angle of 90 °, and the thrust magnetic bearing electromagnets 26 and 27 are arranged on the rotating body. It is arranged in a ring shape surrounding 31. Further, as the radial displacement sensors 28 and 29 and the thrust displacement sensor 30, well-known eddy current type sensors, capacitance type sensors, optical sensors and the like are used. Reference numeral 20 denotes a protective member made of a protective bearing or the like, which uses, for example, a ball bearing and serves both as a radial direction and a thrust direction. A motor rotor 35 is attached to the rotating body 31, and a current is passed through the motor stator 36 by the motor driving device 42 to rotate the rotating body 31. In FIG. 2, reference numeral 38 denotes a casing.

Next, the magnetic bearing control device 1 that controls the magnetic bearing in this reference example will be described.

  The magnetic bearing control device 1 receives the variable weight part replacement signal Sg1 for instructing the replacement of the variable weight part from the outside and the variable weight part replacement signal Sg1 and switches the mode to the received processing content. And adders 2 and 3 for subtracting the displacement signal from the radial displacement sensors 28 and 29 and the thrust displacement sensor 30 and the displacement signal and the position command value in the magnetic levitation mode for performing normal magnetic levitation, A phase compensator 4 for controlling the magnetic attractive force acting between the rotating body 31 and the radial magnetic bearing electromagnets 22, 23, 24, 25 and the thrust magnetic bearing electromagnets 26, 27 based on the outputs of these adders 2, 3. 5 and the power amplifiers 6 and 7 and the variable weight part exchange mode for exchanging the variable weight part 40, a bias current is applied to the radial magnetic bearing electromagnets 22, 23, 24 and 25. A bias command generating unit 10 for applying, a slide command generating unit 15 for outputting a current command 0 for interrupting current application to the thrust magnetic bearing electromagnets 26 and 27, and a position of the rotating body 31 to detect and rotate The variable weight part replacement position detection unit 11 detects that the body 31 is at the replacement position of the variable weight part 40.

  Here, the adders 2 and 3, the phase compensators 4 and 5, and the power amplifiers 6 and 7 constitute a magnetic levitation mode processing unit 13 that controls the magnetic bearing in the magnetic levitation mode. The amplifiers 8 and 9 and the variable weight part replacement position detection unit 11 constitute a variable weight part replacement mode processing unit 14. The power amplifier 6 and the power amplifier 8 of the radial magnetic bearing control device can be shared. Further, the power amplifier 7 and the power amplifier 9 having the thrust magnetic bearing control structure can be shared.

  Next, the operation will be described. First, since it is necessary to always function as a bearing in the normal state, when the mode discriminating unit 12 receives the magnetic levitation mode from the variable weight part replacement signal Sg1, the displacement of the rotating body 31 is detected by the radial displacement sensors 28, 29, Detected by the thrust displacement sensor 30, the output signal is applied to the adders 2 and 3. In the adders 2 and 3, the output signal is subtracted from the command position (target position) of the rotating body 31, and the subtracted signal is input to the phase compensators 4 and 5, and the output from the phase compensators 4 and 5 The power amplifiers 6 and 7 are operated to pass current through the radial magnetic bearing electromagnets 22, 23, 24, and 25 and the thrust magnetic bearing electromagnets 26 and 27, so that the radial magnetic bearing electromagnets 22, 23, 24, and 25 and the radial magnetic bearing rotor 33 are operated. , 34, and the magnetic attraction force generated between the thrust magnetic bearing electromagnets 26, 27 and the thrust magnetic bearing rotor 39 controls the floating position of the rotating body 31 in the radial direction and the thrust direction. When no current is applied to the radial magnetic bearing electromagnets 22, 23, 24, 25 and the thrust magnetic bearing electromagnets 26, 27, the rotating body 31 is supported by the protection member 20. The rotation direction of the rotating body 31 is controlled by the motor driving device 42.

  Next, when the variable weight unit 40 is replaced, when the mode discriminating unit 12 receives from the variable weight unit exchange signal Sg1 that it is in the variable weight unit exchange mode, the mode discriminating unit 12 causes the variable weight unit to be changed from the magnetic levitation processing mode. Processing shifts to exchange mode. In the variable weight part replacement mode processing unit 14, first, application of current to the radial magnetic bearing electromagnets 22, 23, 24, 25 and the thrust magnetic bearing electromagnets 26, 27 is stopped. Next, the bias command generator 10 is set so as to apply a bias current only to a predetermined radial magnetic bearing electromagnet, for example, the radial magnetic bearing electromagnets 22 and 24. The electromagnet to which the bias current is applied is determined in consideration of the direction of the force received by the rotating body 31 from a tool changing arm (not shown) installed in the processing machine at the time of tool change.

In this reference example , when the axial direction of the magnetic bearing device is installed in the vertical direction (vertical type), the current command is set to 0 in order to stop the current application to the thrust magnetic bearing electromagnets 26 and 27. As a result, the rotating body 31 comes into contact with the thrust support side of the protection member 20. As a method of not applying current to the thrust magnetic bearing electromagnets 26 and 27, the driving element may not be operated so that current is not applied to the thrust magnetic bearing electromagnets 26 and 27 inside the power amplifier 9. Next, a bias current is applied to the set radial magnetic bearing electromagnets 22 and 24. As a result, the rotating body 31 moves in the determined direction and comes into contact with the radial support side of the protection member 20.

  In the tool change, it is necessary to keep the position of the arm installed on the processing machine side and the rotating body 31 at a predetermined place. This position is used as a tool change point. The outputs of the radial displacement sensors 28 and 29 and the thrust displacement sensor 30 are input to the variable weight part replacement position detector 11 to determine whether or not the rotating body 31 has moved to the tool change point. When the rotator 31 has moved to the tool change point, the operation moves to the tool change operation. When the rotating body 31 cannot move to the tool change point, the application of the bias current to the radial magnetic bearing electromagnets 22 and 24 is once stopped and the bias current is applied again.

  Then, the variable weight portion replacement position detector 11 determines again whether or not the rotating body 31 has moved to the tool replacement point. When the rotator 31 has moved to the tool change point, the operation moves to the tool change operation. When the rotating body 31 cannot move to the tool change point, the above process is retried a predetermined number of times. If the rotating body 31 cannot be moved to the tool change point after retrying the determined number of times, the tool change operation is stopped and an error is reported.

  Next, the tool change operation will be described. A tool holder 37 holding a tool 32 is attached to the tip of the rotating body 31, and clamping and unclamping of the tool holder 37 with respect to the rotating body 31 is controlled by a draw bar 70 provided inside the rotating body 31.

  FIG. 3 shows a configuration of a draw bar 70 provided in the rotating body 31. The draw bar 70 provided with a clamp portion 77 for clamping the tool holder 37 at the tip is urged backward by a spring 71. In this state, it is accommodated in the rotating body 31 and is configured to be able to advance toward the tip side against the bias of the spring 71 by pressurizing the hydraulic cylinder 72 in the tip direction. The clamp portion 77 at the tip is formed so that it opens when the drawbar 70 is advanced by the hydraulic cylinder 72 and closes when the hydraulic pressure of the hydraulic cylinder 72 is released and the drawbar 70 is retracted by the bias of the spring 71. After the rotator 31 moves to the tool change point, the tool change arm grips the tool holder.

  Next, when the draw bar 70 moves forward, the clamp portion 77 opens and enters an unclamped state, so that the tool holder 37 that has been clamped can be removed, and the arm pulls out the tool holder. Next, in this unclamped state, the arm inserts a new tool holder 37 into the clamp portion 77 by the operation of the processing machine. Next, when the hydraulic pressure of the hydraulic cylinder 72 is released and the draw bar 70 is retracted, the clamp holder 77 is closed and the tool holder 37 is clamped, and the tool holder 37 is attached to the rotating body 31.

  In order to detect the movement position of the hydraulic cylinder 72, a clamp sensor 74 and an unclamp sensor 75, which are state detection sensors, and a sensor target 73 are provided. These sensors are constituted by, for example, proximity switches, the clamp sensor 74 is when the draw bar 70 is in the clamp position, that is, the retracted position, and the unclamp sensor 75 is when the draw bar 70 is in the unclamp position, that is, the forward position. Each is turned on.

  After the tool is changed in this way, the application of the bias current to the radial magnetic bearing electromagnets 22 and 24 is stopped. Next, the mode discriminating unit 12 confirms that the instruction of the variable weight part replacement signal Sg1 is the magnetic levitation mode, shifts to the magnetic levitation mode, and enters the magnetic levitation state.

According to the configuration of the present embodiment, when the automatic tool change, the bias current is applied to the radial magnetic bearing electromagnet set, the rotary body Ri by the positioning to tool change point, it is installed in the processing machine to the rotating body Thus, it is possible to provide a magnetic bearing spindle that can perform tool change even when force is applied from an arm that is present, has high reliability, and can perform automatic tool change in a short time.

(Working-shaped state)
The reference example was a case where the axial direction of the magnetic bearing device was installed in the vertical direction (vertical shape). In the case of this vertical type, if no current is applied to the thrust magnetic bearing electromagnet, the rotating body will be in contact with the thrust support side of the protective bearing due to gravity, so the tool change point in the thrust direction should be a fixed position. Can do.

However, when the axial direction of the magnetic bearing device is installed in a direction 90 ° to the vertical direction (horizontal), it is necessary to control the thrust direction for positioning. Exemplary type state is obtained by taking into account the structure of such a lateral.

Figure 4 is a block diagram showing an overall configuration of a magnetic bearing device definitive in practice forms state of the present invention. In addition, it is the same as that of the structure of the said reference example fundamentally, Comprising: The same code | symbol is attached | subjected to the member corresponding to the member demonstrated in FIGS. 1-3, and detailed description is abbreviate | omitted.

As shown in FIG. 4, exemplary type state is provided with a bias command generating section 16 to the thrust magnetic bearing control device of the variable parts exchange mode processing unit 14. In the first embodiment, the bias current is applied only to the radial magnetic bearing electromagnets 22 and 24 set in the variable weight part replacement mode processing unit 14 in the variable weight part replacement mode at the time of automatic tool change. In addition to the set radial magnetic bearing electromagnets 22 and 24, a bias current is applied to either the thrust magnetic bearing electromagnet 26 or 27 by the bias command generator 16 and the power amplifier 9, and the rotating body is moved to the tool positioning point. 31 is fixed. Other configurations and operations are the same as those in the reference example .

According to the configuration according to the exemplary shape condition, even when the installed magnetic bearing apparatus in horizontal, in the automatic tool change, the bias current is applied to the radial magnetic bearing electromagnets and a thrust magnetic bearing electromagnet set, the tool exchange rotator By positioning at the point, the magnetic bearing can perform tool change even when force is applied to the rotating body from the arm installed on the processing machine, and it is highly reliable and can automatically change tools in a short time. A main shaft can be provided.

  Since the present invention is highly reliable and enables tool change in a short time, a grinding machine (grinding center) capable of unmanned machining of a workpiece such as a machining center that requires tool change is required. It can also be applied to applications.

The block diagram which shows the whole structure of the magnetic bearing apparatus in the reference example of this invention Sectional view showing a specific example of a magnetic bearing device definitive in Reference Examples and shaped state Sectional view showing a configuration of a draw bar of a magnetic bearing device definitive in Reference Examples and shaped state Block diagram illustrating the overall configuration of a magnetic bearing device definitive in practice forms state of the present invention Explanatory drawing for demonstrating the control method of the spindle head of the conventional magnetic bearing apparatus Front view showing the main part of a vertical machining center to which a conventional magnetic bearing device is applied, partly in a block diagram centering on the spindle head

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Magnetic bearing control apparatus 2, 3 Adder 4, 5 Phase compensator 6, 7, 8, 9 Power amplifier 10, 16 Bias command generation part 11 Variable weight part replacement position detection part 12 Mode discrimination | determination part 13 Magnetic levitation mode processing part 14 Variable weight part replacement mode processing part 15 Thrust command generating part 20 Protective members 22, 23, 24, 25 Radial magnetic bearing electromagnets 26, 27 Thrust magnetic bearing electromagnets 28, 29 Radial displacement sensor 30 Thrust displacement sensor 31 Rotating body 32 Tool 33 , 34 Radial magnetic bearing rotor 35 Motor rotor 36 Motor stator 37 Tool holder 38 Casing 39 Thrust magnetic bearing rotor 40 Variable weight section 41 Main shaft 42 Motor drive device 70 Drawbar 71 Spring 72 Hydraulic cylinder 73 Sensor target 74 Clamp sensor 75 Unclamp sensor Sg1 Variable The amount part exchange signal

Claims (2)

In the magnetic bearing device for controlling the levitation by the control current of the radial magnetic bearing electromagnet and the thrust magnetic bearing electromagnet,
A mode discriminating unit for discriminating a magnetic levitation mode and a variable weight part exchange mode based on a variable weight part exchange signal applied from the outside when exchanging the variable weight part attached to the rotating body;
A magnetic levitation mode processing unit for controlling the magnetic levitation bearing of the radial magnetic bearing electromagnet and the thrust magnetic bearing electromagnet according to a signal from the mode determination unit; and the radial magnetism when the variable weight unit is replaced by a signal from the mode determination unit. A bias command generating unit for applying a bias current to the bearing electromagnet, a bias command generating unit for applying a bias current to the thrust magnetic bearing electromagnet, and the rotating body moved to the replaceable position of the variable weight unit. A magnetic bearing device, comprising: a variable weight part replacement mode processing unit configured to include a variable weight part replacement position detecting unit for determining this. When exchanging the variable weight portion mounted on the rotating body controlled to fly by the control current of the radial magnetic bearing electromagnet and the thrust magnetic bearing electromagnet, a bias current is applied to the radial magnetic bearing electromagnet so that the rotating body becomes a radial protective member. with contacting, variable parts by replacing the magnetic bearing device you characterized by positioning in contact with the rotating body to the thrust protection member by applying a bias current to the thrust magnetic bearing electromagnet.

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