JP2021112037A - Molding machine and motor - Google Patents

Abstract

To provide a motor for obtaining a desired output by suppressing superposition of harmonics of, what is called, a slot permeance component caused by difference in magnetic unevenness between teeth (an electromagnetic steel plate) and a slot (air) on a voltage waveform, and an injection molding machine having the motor for obtaining the desired output.SOLUTION: An injection molding machine includes a motor 10. The motor 10 has a stator 12 and a rotor 11. The stator 12 magnetically saturates in teeth 122 at a predetermined output of the motor 10.SELECTED DRAWING: Figure 2

Description

The present invention relates to a molding machine and a motor.

Conventionally, an electric molding machine such as an injection molding machine that drives a motor to perform a molding operation is known (see, for example, Patent Document 1).
In a motor for this type of molding machine, harmonics of a so-called slot permeance component, which is caused by the difference in magnetic unevenness between the teeth (electromagnetic steel plate) and the slot (air), are superimposed on the voltage waveform. If the wave height of this harmonic component is high, as shown in FIG. 6, the terminal voltage of the motor exceeds the power supply voltage, and the voltage waveform is distorted. As a result, there is a possibility that a desired output cannot be obtained because a sufficient current cannot be passed.

Japanese Patent No. 6315559

The present invention has been made in view of the above circumstances, and an object of the present invention is to obtain a desired motor output.

The present invention is a molding machine including a motor.
The motor has a stator and a rotor.
The stator is configured to be magnetically saturated at the teeth at a predetermined output of the motor.

Further, the present invention is a motor having a stator and a rotor.
The stator has a configuration in which the ratio β of the tooth width to the outer peripheral circumference of the rotor for one slot satisfies the following equation (1).
0.45 ≤ β ≤ 0.52 ... (1)

According to the present invention, a desired motor output can be obtained.

It is a figure which shows the injection molding machine which concerns on this embodiment. (A) is a cross-sectional view of the motor of the present embodiment, and is a partially enlarged view of (b) and (a). It is a BH diagram of the stator, (b) is a diagram showing the voltage amplitude of the harmonic component of the terminal voltage, and (c) is a diagram showing the terminal voltage waveform when the motor is driven. It is a figure which shows (a) the change of the torque, the voltage wave height value, the maximum rotation speed and the relative magnetic permeability of a stator with respect to the ratio of a tooth width, and (b) is a figure which shows the change of the output of a motor. It is a figure which shows the change of the relative magnetic permeability with respect to a magnetic field and a magnetic flux density. It is a figure which shows the terminal voltage waveform at the time of driving in a conventional motor.

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

[Overall configuration of injection molding machine]
FIG. 1 is a diagram showing an injection molding machine 1 according to the present embodiment.
As shown in this figure, the injection molding machine 1 according to the present embodiment includes an injection device 20 that melts and injects a molding material, a plasticization moving device 30 that conveys the injection device 20, and a gold that is filled with the molding material. It includes a mold clamping device 50 that moves the mold device 40, and an ejector device 60 that pushes the solidified molded product out of the mold device 40.

The mold device 40 includes a fixed mold 41 held by the fixed platen 51 and a movable mold 42 held by the movable platen 52. The mold clamping device 50 has a mold clamping motor 53 which is a three-phase motor, and when the mold clamping motor 53 is driven, the movable platen 52 holding the movable mold 42 moves to open and close the mold device 40. And mold clamping are performed. The injection device 20 has an injection motor 21 which is a three-phase motor, and the screw 22 is translated and moved by the drive of the injection motor 21, and the molding material is injected from the heating cylinder 23. Further, the injection device 20 has a measuring motor 24 which is a three-phase motor, and the screw 22 is rotated by the driving of the measuring motor 24 to supply the molding material from the hopper 25 to the heating cylinder 23. The plasticized moving device 30 has a plasticized moving motor 31 which is a three-phase motor, and the movable portion operates by driving the plasticized moving motor 31. The ejector device 60 has an eject motor 61 which is a three-phase motor, and the moving portion operates by driving the eject motor 61.

The motor 10 according to the present embodiment is applied to at least one of the injection motor 21, the weighing motor 24, the thermoplastic transfer motor 31, the mold clamping motor 53, and the eject motor 61 described above. ..

[Motor configuration]
2A and 2B are views showing a motor 10 according to the present embodiment, in which FIG. 2A is a cross-sectional view and FIG. 2B is a partially enlarged view of FIG. 2A. Note that the windings are not shown in FIG.
As shown in this figure, the motor 10 of the present embodiment is a synchronous motor of an IPM (Interior Permanent Magnet) motor. The motor 10 includes a cylindrical rotor (rotor) 11 and a stator (stator) 12 arranged on the outer peripheral side of the rotor 11 via a predetermined gap G.

The rotor 11 includes a cylindrical rotor core 111 fitted on the outer circumference of a rotating shaft (not shown), and a plurality of permanent magnets 112 such as neodymium magnets embedded in the rotor core 111.
In the following description, the direction along the central axis Ax of the cylindrical rotor 11 is the "axial direction", the direction perpendicular to the central axis Ax is the "diameter direction", and the rotation direction centered on the central axis Ax is "axial direction". It is called "circumferential direction". Further, the central axis of the stator 12 coincides with the central axis Ax of the rotor 11.

The stator 12 includes a cylindrical stator yoke 121 and a plurality of teeth 122 extending radially inward from the inner peripheral surface of the stator yoke 121. The stator yoke 121 and the plurality of teeth 122 form a stator core made of an integral laminated steel plate.
A winding (coil) (not shown) is inserted into each slot 123 between the teeth 122 adjacent to each other in the circumferential direction so as to be wound around the teeth 122. In this embodiment, the winding is wound in a distributed winding.

The teeth 122 of the stator 12 are formed to have a predetermined tooth width Wt.
Specifically, the tooth width Wt is formed so that the ratio β of the tooth width Wt to the rotor outer diameter peripheral length for one slot satisfies the following equation (1).
0.45 ≤ β ≤ 0.52 ... (1)
Here, the rotor outer diameter peripheral length for one slot is the length corresponding to one of the slots 123 among the peripheral lengths of the rotor 11 in the outer diameter D. That is, the ratio β of the teeth width Wt is given by β = Wt / (πD / S). However, D is the outer diameter of the rotor 11, and S is the number of slots 123.

Hereinafter, the action / effect of the motor 10 (stator 12) satisfying the above equation (1) will be described.
FIG. 3A is a diagram showing the magnetic characteristics of the stator 12 (stator core), and is a diagram BH showing the relationship between the magnetic field (strength) H and the magnetic flux density B, and is FIG. 3B. ) Is a diagram showing the voltage amplitude of the harmonic component of the terminal voltage, and FIG. 3 (c) is a diagram showing the terminal voltage waveform when the motor 10 is driven. Of these, FIGS. 3 (b) and 3 (c) show examples of calculation and analysis when β is 0.45 and 0.55. Further, FIG. 4A is a diagram showing changes in torque, voltage wave height, maximum rotation speed, and relative magnetic permeability of the stator 12 with respect to the ratio β of the tooth width Wt, and FIG. 4B is a diagram showing changes in the tooth width Wt. It is a figure which shows the change of the output of a motor 10 with respect to the ratio β of. In FIG. 4, the vertical axis is shown as a ratio (pu: per unit) based on the value when β = 0.55.

When the ratio β of the tooth width Wt is within the range of the above formula (1), the teeth 122 is magnetically saturated when a predetermined amount of current is applied (for example, at the maximum output of the motor 10). That is, at this time, as shown in FIG. 3A, the magnetic flux density of the stator 12 is substantially saturated when β is 0.52 or less. Therefore, it becomes difficult for the magnetic flux to pass through the teeth 122, and the difference in magnetic unevenness between the teeth 122 and the slot 123 adjacent to the teeth 122 becomes small.
This magnetic unevenness superimposes harmonic components due to slot permeance on the voltage waveform. This slot permeance component is generally represented by 2q ± 1 using the number of slots q for each pole and each phase of the motor 10. Here, q = S / (m × P), m: number of phases, P: number of poles (number of magnets). In the present embodiment, as shown in FIG. 3B, for example, β is changed from 0.55 to 0.45 to reduce the difference in magnetic unevenness in the circumferential direction in the stator 12, and to reduce the slot permeance component. It can be greatly suppressed.
As a result, as shown in FIG. 3C, the harmonic component (voltage wave high value) superimposed on the voltage waveform is suppressed to be small, and the voltage waveform is suppressed from exceeding the power supply voltage. As a result, it is possible to avoid a situation in which the current cannot be input due to the voltage waveform exceeding the power supply voltage, and it is possible to suppress a decrease in output.

More specifically, as shown in FIG. 4A, when the ratio β of the tooth width Wt is in the range of 0.4 to 0.52, the torque, the voltage wave height value, and the rotation speed (maximum rotation speed) are almost linear. Change. However, when β exceeds 0.52, the rate of increase of the voltage wave high value increases and the rate of decrease of the rotation speed increases (because it is necessary to lower the terminal voltage by the increase of the voltage wave high value by lowering the rotation speed). ). As a result, as shown in FIG. 4B, the output of the motor, which is the product of torque and rotation speed, is greatly reduced when β exceeds 0.52.
Therefore, the decrease in output can be suppressed by suppressing the ratio β of the teeth width Wt to 0.52 or less while generating torque to a certain degree or more by setting the ratio β of the teeth width Wt to 0.45 or more to increase the output.

In a general industrial motor, the tooth width is designed to be relatively wide from the viewpoint of torque retention, and the tooth is not shaped to cause magnetic saturation.
On the other hand, motors for molding machines such as injection molding machines are required to have a high peak output, and therefore tend to be designed with a larger input current and a wider tooth width than general motors.
On the other hand, in the motor 10 of the present embodiment, the tooth width Wt is narrowed and the magnetic saturation is positively performed as compared with the conventional case, thereby suppressing the harmonics and compensating for the decrease in torque due to the magnetic saturation by the rotation speed. The desired motor output is secured.

In the present embodiment, the ratio β of the teeth width Wt satisfies the above equation (1), but the condition is not limited to this, and the teeth 122 may be magnetically saturated at a predetermined output of the motor 10. As a result, the harmonics of the slot permeance component can be suppressed.
Here, the "magnetic saturation" in the present embodiment means a state in which the magnetic permeability is, for example, 1/10 or less of the maximum value. The magnetic permeability μ is the ratio of the magnetic flux density B and the magnetic field H (B = μH), and is represented by the product of _{the vacuum magnetic permeability μ 0} and the specific magnetic permeability μ _{r of the stator 12. The changes in the relative magnetic permeability μ r} with respect to the magnetic field H and the magnetic flux density B are shown in FIGS. 5 (a) and 5 (b). As shown in this figure, the “magnetic saturation” of the present embodiment means a state in which the magnetic field H and the magnetic flux density B are high and the relative magnetic permeability μ _{r is sufficiently small.}
Further, the "predetermined output" of the motor 10 in which the teeth 122 causes magnetic saturation is defined as the maximum output in the present embodiment, but it may be any time when the rated output or more is output.

[Technical effect of this embodiment]
As described above, according to the present embodiment, the teeth 122 of the stator 12 are magnetically saturated at the predetermined output of the motor 10. As a result, it becomes difficult for the magnetic flux to pass through the teeth 122, and the harmonics of the slot permeance component superimposed on the voltage waveform can be suppressed.
Therefore, it is possible to prevent the harmonics superimposed on the voltage waveform from exceeding the power supply voltage, and thus obtain a desired motor output.

Further, according to the present embodiment, the ratio β of the tooth width Wt to the rotor outer diameter peripheral length for one slot is within the range of 0.45 or more and 0.52 or less.
As a result, as shown in FIG. 4, the motor output can be suitably obtained while avoiding a decrease in the rotation speed.

[others]
Although the embodiment of the present invention has been described above, the present invention is not limited to the above embodiment.
For example, in the above embodiment, the motor 10 is an IPM motor. However, the present invention can be suitably applied to SPM (Surface Permanent Magnet) motors and further to induction motors. Further, the stator 12 (stator core) may be a divided core.
Further, in the motor according to the present invention, the winding may be concentrated winding instead of distributed winding. Further, the motor according to the present invention is not limited to the one provided in the molding machine, and can be widely applied to those other than the molding machine.

Further, in the above embodiment, the motor 10 included in the injection molding machine 1 has been described as an example, but the molding machine according to the present invention may be any as long as it includes a motor, and is not limited to the injection molding machine.
In addition, the details shown in the above-described embodiment can be appropriately changed without departing from the spirit of the invention.

1 Injection molding machine (molding machine)
10 Motor 11 Rotor 12 Stator 121 Stator yoke 122 Teeth 123 Slot D (rotor) outer diameter G Gap Wt Teeth width β Teeth width ratio

Claims (6)

A molding machine equipped with a motor
The motor has a stator and a rotor.
The stator is magnetically saturated at the teeth at a predetermined output of the motor.
Molding machine. In the stator, the ratio β of the tooth width to the outer peripheral circumference of the rotor for one slot satisfies the following equation (1).
The molding machine according to claim 1.
0.45 ≤ β ≤ 0.52 ... (1) The motor is an IPM motor.
The molding machine according to claim 1 or 2. A winding is wound around the stator in a distributed winding manner.
The molding machine according to any one of claims 1 to 3. The predetermined output is the maximum output.
The molding machine according to any one of claims 1 to 4. A motor that has a stator and a rotor.
In the stator, the ratio β of the tooth width to the outer peripheral circumference of the rotor for one slot satisfies the following equation (1).
motor.
0.45 ≤ β ≤ 0.52 ... (1)

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