TW201350307A - Injection molding machine - Google Patents

Abstract

The present invention provides an injection molding machine capable of improving the performance of a linear motor at the start of mold feeding while suppressing the upsizing of the linear motor. The injection molding machine (10) according to the present invention is provided with a three-phase AC type linear motor (28) for driving mold opening and closing operations. The linear motor (28) comprises: a movable element (31) including a plurality of coils (35) aligned at intervals in a direction parallel to the mold opening and closing direction; and a stator (29) including a plurality of permanent magnets (32A, 32B) aligned at intervals in the direction parallel to the mold opening and closing direction, and an air gap (36) is formed between the stator (29) and the movable element (31). The magnetic flux density of a magnetic field formed in the air gap by the permanent magnet to which at least a part of the movable element 31 is adjacent is set higher when the movable element 31 starting up toward a predetermined direction than that when the movable element 31 traveling at the highest speed toward the predetermined direction.

Description

Injection molding machine

The present application claims priority based on Japanese Patent Application No. 2012-054062, filed on March 12, 2012. All contents of the application are hereby incorporated by reference.

The present invention relates to an injection molding machine.

The injection molding machine produces a molded article by filling and solidifying the molten resin in the cavity space of the mold device. The mold device is composed of a fixed mold and a movable mold, and a cavity space is formed between the fixed mold and the movable mold during mold clamping. The mold closing, mold clamping, and mold opening of the mold apparatus are performed by a mold clamping device. As a mold clamping device, a mold clamping device in which a linear motor is used in a mold opening and closing operation and an adsorption force of an electromagnet is used in a mold clamping operation has been proposed (for example, see Patent Document 1).

(previous technical literature) (Patent Literature)

Patent Document 1: International Publication No. 2005/090052

It is desirable to improve the performance of the linear motor at the beginning of the mold delivery. For example, at the beginning of the mold opening, the frictional resistance of the positioning pin formed on one of the fixed mold and the movable die pin and the pin hole formed on the other side, and the adhesion force of the resin of the fixed mold and the movable mold are overcome by It is required to increase the driving force by performing the mold clamping operation by the adsorption force of the residual magnetic flux of the electromagnet or the like. The increase in the driving force is effective in increasing the size of the linear motor, but the installation space of the linear motor that is miniaturized with the injection molding machine is limited.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an injection molding machine capable of suppressing an increase in size of a linear motor and improving the performance of a linear motor at the start of mold delivery.

In order to solve the above problems, an injection molding machine according to an aspect of the present invention includes a three-phase AC type linear motor that drives a mold opening and closing operation, wherein the linear motor has a movable member including parallel a plurality of coils arranged at intervals in a direction of opening and closing of the mold; and a fixing member including a plurality of permanent magnets arranged at intervals in a direction parallel to the opening and closing direction of the mold, and the fixing member and the movable member An air gap is formed therebetween, and a magnetic flux density of the magnetic field formed in the air gap by the permanent magnet approaching at least a portion of the movable member is higher than the movable member when the movable member is started in a predetermined direction Speed to the aforementioned predetermined direction It is higher when walking.

According to the present invention, an injection molding machine capable of suppressing an increase in size of a linear motor and improving the performance of a linear motor at the start of mold delivery is provided.

10‧‧‧ Injection molding machine

11‧‧‧Fixed platen

12‧‧‧ movable platen

13‧‧‧ rear platen

15‧‧‧Fixed mode

16‧‧‧ movable mold

19‧‧‧Molding device

22‧‧‧Adsorption plate

28‧‧‧Line motor

29‧‧‧Fixed parts

30‧‧‧ Fixed Department

32A, 32B‧‧‧ permanent magnet

31‧‧‧ movable parts

33‧‧‧Magnetic teeth

34‧‧‧ magnetic core

35‧‧‧ coil

36‧‧‧Air gap

Fig. 1 is a view showing a state at the start of mold opening (at the end of mold closing) by the injection molding machine according to the first embodiment of the present invention.

Fig. 2 is a view showing a state in which the injection molding machine according to the first embodiment of the present invention starts mold closing (at the time of mold opening).

Fig. 3 is a view showing a state at the start of mold opening of the linear motor of the first embodiment (when the mold is closed).

Fig. 4 is a view showing a state at the start of mold opening of the linear motor of the second embodiment (when the mold closing is completed).

Fig. 5 is a view showing a state at the start of mold opening of the linear motor of the third embodiment (when the mold closing is completed).

In the following, the embodiments for carrying out the invention will be described with reference to the accompanying drawings. Further, the moving direction of the movable platen when the mold is closed is set to the front, and the moving direction of the movable platen when the mold is opened is set to the rear. To explain.

[First Embodiment]

Fig. 1 is a view showing a state at the start of mold opening (at the end of mold closing) by the injection molding machine according to the first embodiment of the present invention. Fig. 2 is a view showing a state in which the injection molding machine according to the first embodiment of the present invention starts mold closing (at the time of mold opening). In the first and second figures, a part of the plurality of coils included in the linear motor is omitted.

In the figure, 10 is an injection molding machine, Fr is a frame of the injection molding machine 10, Gd is a guide composed of two rails laid on the frame Fr, and 11 is a fixed platen. The fixed platen 11 can be disposed on the position adjustment base Ba which is movable along the guide member Gd extending in the mold opening and closing direction (the horizontal direction in the drawing). In addition, the fixed platen 11 can also be placed on the frame Fr.

The movable platen 12 is disposed opposite to the fixed platen 11. The movable platen 12 is fixed to the movable base Bb, and the movable base Bb can travel on the guide Gd. Thereby, the movable platen 12 can be moved in the mold opening and closing direction with respect to the fixed platen 11.

The rear platen 13 is disposed at a predetermined interval from the fixed platen 11 in parallel with the fixed platen 11. The rear platen 13 is fixed to the frame Fr via the leg portion 13a.

Four tie bars 14 (only two of the four tie bars 14 are shown in the drawing) are spanned between the fixed platen 11 and the rear platen 13 . The fixed platen 11 is fixed to the rear platen 13 via a tie rod 14. Along the tie rod 14 The movable platen 12 is disposed in advance and retreat. A guide hole (not shown) for inserting the tie rod 14 is formed at a portion corresponding to the tie rod 14 of the movable platen 12. In addition, a notch portion may be formed instead of the via hole.

A threaded portion (not shown) is formed at a front end portion (right end portion in the drawing) of the tie rod 14, and the nut n1 is screwed and fastened to the screw portion, whereby the front end portion of the tie rod 14 is fixed to the fixed pressure plate 11. The rear end portion of the tie rod 14 is fixed to the rear pressure plate 13.

A fixed die 15 is mounted on the fixed platen 11, and a movable die 16 is mounted on the movable platen 12. The fixed die 15 and the movable die 16 are contacted and separated with the advancement and retreat of the movable platen 12, thereby performing mold closing, mold clamping, and mold opening. . Further, as the mold clamping is performed, a cavity space (not shown) is formed between the fixed mold 15 and the movable mold 16, and the molten resin is filled in the cavity space. The mold device 19 is constituted by the fixed mold 15 and the movable mold 16.

The adsorption plate 22 is disposed in parallel with the movable platen 12. The suction plate 22 is fixed to the slide base Sb via a mounting plate 27, and the slide base Sb can travel on the guide Gd. Thereby, the suction plate 22 advances and retreats more rearward than the rear pressure plate 13. The adsorption plate 22 may be formed of a soft magnetic material. Further, the mounting plate 27 may not be provided, and in this case, the suction plate 22 is directly fixed to the sliding base Sb.

The rod 39 is disposed to be coupled to the suction plate 22 at the rear end portion, and is coupled to the movable platen 12 at the front end portion. Therefore, the rod 39 advances with the advancement of the suction plate 22 at the time of mold closing, and advances the movable platen 12. When the mold is opened, the suction plate 22 is retracted and the movable platen 12 is retracted. Therefore, a through hole for penetrating the rod 39 is formed in the central portion of the rear platen 13 41.

The linear motor 28 is a motor that drives the mold opening and closing operation, and is disposed, for example, between the sliding base Sb to which the adsorption plate 22 is fixed and the frame Fr. Further, the linear motor 28 may be disposed between the movable platen 12 and the frame Fr.

The linear motor 28 is a three-phase synchronous motor of a so-called moving coil type, and includes a fixing member 29 including a plurality of permanent magnets 32A and 32B (see FIG. 3) and a movable member 31 including a plurality of coils 35. The fixing member 29 is formed to be fixed to the frame Fr and corresponds to the movement range of the slide base Sb. The movable member 31 is formed to be fixed to the slide base Sb and opposed to the fixing member 29, and extends over a predetermined range. The position of the movable member 31 is measured by the position sensor 53.

When a predetermined current is supplied to the coil 35 of the movable member 31, the movable member 31 is moved forward and backward by the interaction of the magnetic field generated by the current flowing in the coil 35 and the magnetic field generated by the permanent magnets 32A, 32B. Accordingly, the suction plate 22, the rod 39, and the movable platen 12 are advanced and retracted to perform mold closing and mold opening. The linear motor 28 is feedback-controlled in accordance with the detection result of the position sensor 53 so that the position of the movable member 31 becomes a target value.

The electromagnet unit 37 generates an adsorption force between the rear platen 13 and the adsorption plate 22. This suction force is transmitted to the movable platen 12 via the rod 39, and a mold clamping force is generated between the movable platen 12 and the fixed platen 11.

The electromagnet unit 37 is composed of an electromagnet 49 formed on the side of the rear platen 13 and an adsorption portion 51 formed on the side of the adsorption plate 22. The adsorption portion 51 is formed in a predetermined portion of the adsorption surface (front end surface) of the adsorption plate 22, for example, a portion of the adsorption plate 22 that surrounds the rod 39 and faces the electromagnet 49. And after A predetermined portion of the suction surface (rear end surface) of the pressure plate 13 is formed, for example, around the rod 39 to form a groove 45 of the coil 48 accommodating the electromagnet 49. The magnetic core 46 is formed on the inner side of the groove 45. The coil 48 is wound around the core 46. A portion other than the magnetic core 46 in the rear platen 13 is formed with a yoke 47.

Further, in the present embodiment, the electromagnet 49 is formed separately from the rear platen 13, and the adsorption portion 51 is formed separately from the adsorption plate 22. However, the electromagnet may be formed as a part of the rear platen 13, and the adsorption portion may be formed as an adsorption. A portion of the board 22. Further, the electromagnet and the adsorption portion may be arranged in reverse. For example, the electromagnet 49 can be provided on the side of the adsorption plate 22, and the adsorption portion 51 can be provided on the side of the rear platen 13. Further, the number of the coils 48 of the electromagnet 49 may be plural.

In the electromagnet unit 37, when a current is supplied to the coil 48, the electromagnet 49 is driven and the adsorption portion 51 is adsorbed, whereby a mold clamping force can be generated. The electromagnet 49 performs feedback control based on the detection result of the mold clamping force sensor 55 that detects the mold clamping force so that the mold clamping force reaches the target value. The mold clamping force sensor 55 is configured, for example, by a strain sensor or the like that detects the strain (elongation amount) of the tie rod 14 that is extended in accordance with the mold clamping force. The strain sensor is disposed on at least one tie rod 14.

The control unit 60 includes, for example, a CPU, a memory, and the like, and controls the operation of the line motor 28 and the electromagnet 49 by processing the control program recorded in the memory by the CPU.

Next, the operation of the injection molding machine 10 having the above configuration will be described. The various operations of the injection molding machine 10 are performed under the control of the control unit 60.

The control unit 60 controls the mold closing process. The control unit 60 supplies a current to the coil 35 of the linear motor 28 in the state (opening state) of Fig. 2 to advance the movable platen 12. As shown in Fig. 1, the movable mold 16 is brought into contact with the fixed mold 15. At this time, a gap δ is formed between the rear platen 13 and the adsorption plate 22, that is, between the electromagnet 49 and the adsorption portion 51. In addition, the force required to close the mold is very small compared to the clamping force.

Next, the control unit 60 controls the mold clamping process. The control unit 60 supplies a current to the coil 48 of the electromagnet 49, and adsorbs the adsorption unit 51 on the electromagnet 49. This adsorption force is transmitted to the movable platen 12 via the rod 39, thereby generating a mold clamping force between the movable platen 12 and the fixed platen 11. The molten resin is filled in the cavity space of the mold device 19 in the mold clamping state. When the resin is cooled and solidified, the control unit 60 cuts off the supply of electric power to the coil 48 of the electromagnet 49, and releases the mold clamping force.

Thereafter, the control unit 60 controls the mold opening process. The control unit 60 supplies a current to the coil 35 of the linear motor 28 to move the movable platen 12 backward. As shown in Fig. 2, the movable mold 16 is retracted to perform mold opening. After the mold is opened, the molded article can be pushed out from the movable mold 16.

Next, the configuration of the linear motor 28 will be described in detail based on Fig. 3 . Fig. 3 is a view showing a state at the start of mold opening of the linear motor of the first embodiment (when the mold is closed). In Fig. 3, a permanent magnet having a high residual magnetic flux density is indicated by black, and a permanent magnet having a low residual magnetic flux density is indicated by white. In addition, the direction of the arrow in Fig. 3 represents the mold opening direction.

The linear motor 28 is a 3-phase AC type motor, and is provided by a fixing member 29 and The moving member 31 is constructed.

The fixing member 29 includes a fixing portion 30 and a plurality of permanent magnets 32A and 32B which are provided in the fixing portion 30 and are arranged at intervals in a direction parallel to the opening and closing direction of the mold. The plurality of permanent magnets 32A and 32B are arranged at equal intervals Pm, and the magnetic poles on the side of the movable member 31 are alternately magnetized by the N pole and the S pole. The magnetization directions of the permanent magnets 32A and 32B are parallel to the axial direction of the coil 35 of the mover 31. For example, a rare earth magnet is used as the permanent magnets 32A and 32B.

The movable member 31 includes a comb-shaped magnetic core 34 and a plurality of coils 35 wound around a plurality of magnetic pole teeth 33 formed on the magnetic core 34 in a concentrated winding (fractional slot winding). The magnetic pole teeth 33 protrude toward the fixing member 29. The coils 35 are arranged at a constant pitch Pt in a direction parallel to the opening and closing direction of the mold. The coil pitch Pt is smaller than the magnet pitch Pm (for example, the case of 8 poles and 9 slots shown in Fig. 3, Pt = 8/9 × Pm).

The plurality of coils 35 are arranged in a direction parallel to the opening and closing direction of the mold, and the plurality of coils 35 are arranged in a plurality of (three in FIG. 3) U-phase coils 35 and a plurality of (three in FIG. 3) V-phase coils 35 and A plurality of (three in FIG. 3) W-phase coils 35 are arranged in order.

When the three-phase alternating current is supplied to the plurality of coils 35 at the start of the mold opening, the mover 31 starts moving backward from the front end of the stroke. After the movable member 31 is accelerated to the set speed, it is moved rearward at the set speed, and then decelerated and stopped at the rear end of the stroke.

On the other hand, when the three-phase alternating current is supplied to the plurality of coils 35 at the start of mold closing, the mover 31 starts moving from the rear end of the stroke toward the front. After the movable member 31 is accelerated to the set speed, the speed is forwarded at the set speed. Move, then slow down and stop at the front end of the trip. At this time, the fixed mold 15 abuts against the movable mold 16.

At the start of mold opening and at the start of mold closing, the waveform of the current flowing to each coil 35 is adjusted to reverse the moving direction of the movable member 31.

In the present embodiment, when at least a portion of the movable member 31 (for example, a portion of the W-phase coil 35) is started in a predetermined direction (for example, a mold opening direction), the permanent magnet 32A having a high residual magnetic flux density is approached at the highest speed. When traveling in a predetermined direction (for example, a mold opening direction), the permanent magnet 32B having a low residual magnetic flux density is approached. Here, the specific coil approaching a specific permanent magnet means that at least a part of the specific permanent magnet exists in a range within ±1/2×Pt in a direction parallel to the mold opening and closing direction centering on the central axis of the specific coil. The permanent magnet 32A having a high residual magnetic flux density can be partially disposed in the vicinity of one end (for example, the front end) of the stroke of the movable member 31, and the permanent magnet 32B having a low residual magnetic flux density can be disposed in other regions.

The residual magnetic flux density depends on, for example, the material of the permanent magnets 32A and 32B, that is, the kind or purity of the rare earth element. For example, the residual magnetic flux density of the neodymium magnet is higher than the residual magnetic flux density of the samarium cobalt magnet, and is also a neodymium magnet, and the amount of residual flux is higher as the amount of the sintering aid is less and the purity is higher.

When the size G of the air gap 36 formed between the fixing member 29 and the movable member 31 is the same, and the thickness H of the magnetization direction of the permanent magnet is the same, the residual magnetic flux density of the permanent magnet becomes higher, and the permanent magnets are used by the permanent magnets. The magnetic flux density of the magnetic field generated in the air gap 36 (specifically, within a range of ±1/2 Pm from the center of each permanent magnet) becomes higher.

Therefore, the magnetic flux density of the magnetic field formed in the air gap 36 by the permanent magnet approaching at least a portion of the movable member 31 (for example, a portion of the W-phase coil 35) is activated when starting in a predetermined direction. The highest speed is higher when walking in a predetermined direction.

When the current value of the current flowing through the coil 35 is the same, the magnetic flux density generated in the air gap 36 by the permanent magnet becomes higher, and the torque is increased, so that the movable member 31 is oriented in a predetermined direction (for example, the mold is opened). Direction) can get a large thrust when starting. Therefore, at the start of the mold delivery (for example, when the mold opening is started), a large thrust can be obtained, and the performance of the linear motor 28 can be improved, so that it is not necessary to increase the size of the linear motor 28.

When the magnetic flux density formed in the air gap 36 by the permanent magnet is increased, the induced voltage constant is increased, and when the movable member 31 is activated, the speed of the movable member 31 is slowed, and the change in the magnetic flux passing through the coil 35 is small. Therefore, the actually generated induced voltage is small. Since the induced voltage is small, large output of a power source for flowing a current of a desired current value through the coil 35 becomes unnecessary.

When the movable member 31 travels at the highest speed, the magnetic flux density generated in the air gap 36 by the permanent magnet becomes low, so that the induced voltage constant becomes low, and the increase in the induced voltage actually generated is suppressed. Therefore, large output of a power source for flowing a current of a desired current value through the coil 35 becomes unnecessary.

Thus, the magnetic flux density generated in the air gap 36 is adjusted in accordance with the position of the movable member 31, whereby a large thrust can be obtained when the movable member 31 is started in a predetermined direction, and the restriction of the output voltage of the power source is alleviated. Further, since the permanent magnet 32A having a high residual magnetic flux is used in part, it is possible to suppress an increase in cost due to the high performance of the permanent magnet. These effects are more remarkable when the permanent magnet 32A having a high magnetic flux density is partially disposed near one end (and/or both ends) of the stroke of the movable member 31.

However, in the linear motor 28 of the concentrated winding, the specific phase (for example, the W phase) coil 35 of the three-phase coil 35 has a tendency to contribute to the thrust of the movable member 31, and the coil having a higher thrust contribution rate is replaced by the power frequency synchronization. The position of the movable member 31 is replaced. A coil with a higher thrust contribution rate sometimes spans the coils of two phases. The coil 35 having a higher thrust contribution rate can be determined by the relative relationship between the permanent magnets 32A and 32B at the time of starting and the coil 35, and the positions of the phases are equal, and can be confirmed in advance by simulation. A large thrust is generated by the magnetic flux concentration portion (the portion where the magnetic flux from the fixing member 29 is concentrated) in the movable member 31.

When the movable member 31 is started in the predetermined direction, the portion where the thrust contribution rate is high, that is, the magnetic flux concentration portion (for example, the W-phase coil 35) is close to the permanent magnet 32A having a high residual magnetic flux density, the larger the current can be obtained with less current. The thrust is better and more efficient. The portion where the thrust contribution rate is low (for example, the U-phase and V-phase coils) can always approach the permanent magnet 32B having a low residual magnetic flux density regardless of the position of the movable member 31.

As shown in Fig. 3, when the movable member 31 is started in a predetermined direction, a portion having a higher thrust contribution rate (for example, the W-phase coil 35) can be disposed in a portion having a lower thrust contribution ratio (for example, U-phase and V-phase). The coil 35) is further on the side opposite to the predetermined direction.

Further, when the movable member 31 is started in a predetermined direction, a portion having a high thrust contribution rate (for example, the V-phase coil 35) can be used as a reference on a side opposite to the predetermined direction with a lower thrust contribution ratio (for example, a W-phase coil). 35). At this time, the portion where the thrust contribution rate is low (for example, the W-phase coil 35) can approach the permanent magnet 32A having a high residual magnetic flux density when the movable member 31 is started in a predetermined direction. The permanent magnets 32A having a high residual magnetic flux density are continuously arranged on the side opposite to the predetermined direction (for example, the mold opening direction) of the permanent magnets 32B having a lower residual magnetic flux density. Therefore, when the permanent magnet 32A having a high residual magnetic flux density is disposed between the permanent magnets 32B having a low residual magnetic flux density, the pulsation of the torque is suppressed when the movable member 31 moves.

Further, in the present embodiment, as shown in FIG. 3, the permanent magnet 32A having a high residual magnetic flux density is partially disposed near one end of the stroke of the mover 31, but when the upper limit value of the output voltage of the power source is high, It is disposed over a range greater than or equal to the length of the movable member 31.

[Second Embodiment]

Fig. 4 is a view showing a state at the start of mold opening of the linear motor of the second embodiment (when the mold closing is completed). The direction of the arrow in Fig. 4 indicates the direction of the mold opening.

The linear motor 128 shown in Fig. 4 drives the mold opening and closing operation in place of the linear motor 28 shown in Fig. 3 . The linear motor 128 is a three-phase AC type motor and is composed of a fixing member 129 and a movable member 131.

The fixing member 129 includes a fixing portion 130 and is disposed on the fixing portion 130 and A plurality of permanent magnets 132A and 132B are arranged at intervals in a direction parallel to the mold opening and closing direction. The plurality of permanent magnets 132A and 132B are arranged at equal intervals Pm, and the magnetic poles on the movable member 131 side are alternately magnetized by the N pole and the S pole. The magnetization directions of the permanent magnets 132A and 132B are parallel to the axial direction of the coil 135 of the mover 131. For example, a rare earth magnet is used as the permanent magnets 132A and 132B.

The movable member 131 includes a comb-shaped magnetic core 134 and a plurality of coils 135 wound in a concentrated winding (fractional slot winding) on a plurality of magnetic pole teeth 133 formed on the magnetic core 134. The magnetic pole teeth 133 protrude toward the fixing member 129. The plurality of coils 135 are arranged at an equal pitch Pt in a direction parallel to the mold opening and closing direction. The coil pitch Pt is smaller than the magnet pitch Pm (for example, the case of 8 poles and 9 slots shown in Fig. 4, Pt = 8/9 × Pm).

The plurality of coils 135 are arranged in a direction parallel to the opening and closing direction of the mold, and the phases are arranged separately. For example, as shown in FIG. 3, the order of the three U-phase coils 135, the three V-phase coils 135, and the three W-phase coils 135 is as follows. arrangement.

When the three-phase alternating current is supplied to the plurality of coils 135 at the start of mold opening, the mover 131 starts moving backward from the front end of the stroke. After the movable member 131 is accelerated to the set speed, it moves forward at the set speed, then decelerates and stops at the rear end of the stroke.

On the other hand, when the three-phase alternating current is supplied to the plurality of coils 135 at the start of mold closing, the mover 131 moves forward from the rear end of the stroke. The movable member 131 is accelerated to the set speed and then moved forward at the set speed, and then decelerated and stopped at the front end of the stroke. At this time, the fixed mold 15 abuts against the movable mold 16.

At the start of mold opening and at the start of mold closing, the waveform of the current flowing to each coil 135 is adjusted to reverse the moving direction of the movable member 131.

In this embodiment, when at least a portion of the movable member 131 (for example, a portion of the W-phase coil 135) is started in a predetermined direction (for example, a mold opening direction), a narrow air gap 136A is formed between the movable member 131 and the fixing member 129. When traveling at a highest speed in a predetermined direction (for example, a mold opening direction), a wider air gap 136B is formed between the fixing member 129 and the fixing member 129. The stage difference portion corresponding to the difference in size between the air gap 136A and the air gap 136B is formed on the surface of the fixing portion 130 to which the permanent magnets 132A and 132B are fixed. The narrower air gap 136A may be partially formed near one end (e.g., the front end) of the stroke of the movable member 131, and a wider air gap 136B may be formed in other regions.

When the residual magnetic flux density of the permanent magnets 132A and 132B is the same and the magnetization direction thickness H of the permanent magnets 132A and 132B is the same, the air gap becomes narrower, and the permanent magnets 132A and 132B are generated in the air gap (specifically In other words, the magnetic flux density of the magnetic field in the range of ±1/2 Pm from the center of each of the permanent magnets 132A and 132B is higher.

Therefore, in the present embodiment, as in the first embodiment, the magnetic flux density of the magnetic field formed in the air gap is formed by the permanent magnet which is close to at least a part of the movable member 131 (for example, a part of the W-phase coil 135). It is higher when starting in a predetermined direction than when traveling in a predetermined direction at the highest speed.

When the current value of the current flowing through the coil 135 is the same, the magnetic flux density generated by the permanent magnet in the air gap becomes higher, and the generated torque is increased, so that the movable member 131 is oriented in a predetermined direction (for example, the mold opening direction). ) A large thrust can be obtained at the start. Therefore, at the start of the mold delivery (for example, at the start of mold opening), a large thrust can be obtained and the performance of the line motor 128 can be improved, so that it is not necessary to increase the size of the line motor 128.

When the magnetic flux density generated in the air gap by the permanent magnet becomes high, the induced voltage constant becomes high, but when the movable member 131 is started, the speed of the movable member 131 is slow, and the change in the magnetic flux passing through the coil 135 is small, so the actual The induced voltage generated is small. Since the induced voltage is small, large output of a power source for flowing a current of a desired current value through the coil 135 becomes unnecessary.

When the movable member 131 travels at the highest speed, the magnetic flux density generated in the air gap by the permanent magnet is lowered, so that the induced voltage constant is lowered, and the increase in the induced voltage actually generated is suppressed. Therefore, large output of a power source for flowing a current of a desired current value through the coil 135 becomes unnecessary.

In this manner, the magnetic flux density generated in the air gaps 136A, 136B is adjusted corresponding to the position of the movable member 131, whereby a large thrust can be obtained when the movable member 131 is started in a predetermined direction, and the restriction of the output voltage of the power source is alleviated. This effect is more remarkable when the narrow air gap 136A is partially disposed near one end (and/or both ends) of the stroke of the movable member 131.

When the movable member 131 is started in a predetermined direction, if the winding thrust contribution rate is higher, that is, the magnetic pole tooth 133 of the magnetic flux concentration portion (for example, the W-phase coil 135) forms a narrow air gap 136A with the fixing member 129. , it is possible to obtain a larger thrust with less current and is more efficient. Winding push The magnetic pole teeth 133 of the portion where the force contribution rate is low (for example, the U phase and the V phase coil 135) can always form a wider air gap 136B with the fixing member 129 regardless of the position of the movable member 131.

As shown in Fig. 4, when the movable member 131 is started in a predetermined direction, a portion having a higher thrust contribution rate (for example, the W-phase coil 135) can be disposed in a portion having a lower thrust contribution ratio (for example, U-phase and V-phase). The coil 135) is on the opposite side to the predetermined direction.

Further, when the movable member 131 is started in a predetermined direction, a portion having a high thrust contribution rate (for example, the V-phase coil 135) can be used as a reference, and a portion having a lower thrust contribution rate (for example, a W phase) on the side opposite to the predetermined direction can be used. Coil 135). At this time, the magnetic pole teeth 133 of the portion where the thrust contribution rate is low (for example, the W-phase coil 135) is wound, and a narrow air gap can be formed between the movable member 131 and the fixing member 129 when the movable member 131 is started in a predetermined direction. 136A. The narrower air gap 136A is continuously formed on the side of the relatively wide air gap 136B which is opposite to the predetermined direction (for example, the mold opening direction). Therefore, the pulsation of the torque is suppressed as the movable member 131 moves as compared with when the narrow air gap 136A is sandwiched between the wider air gaps 136B.

Further, in the present embodiment, as shown in FIG. 3, the narrow air gap 136A is partially formed near the end of the stroke of the movable member 131, but when the upper limit value of the output voltage of the power source is high, it may be greater than or It is formed equal to the range of the length of the movable member 131.

Further, in the present embodiment, the stepped portion is formed on the surface on which the permanent magnets 132A and 132B are fixed to the fixing portion 130, but the surface may be flat. Faceted. At this time, a permanent magnet having a thickness different in magnetization direction corresponding to a difference in size between the narrower air gap 136A and the wider air gap 136B may be used. At this time, the processing cost of the fixing portion 130 is reduced, and the third embodiment will be described in detail, and the performance of the injection molding machine at the start of the mold delivery can be further improved by partially arranging the permanent magnet having a thick magnetization direction.

[Third embodiment]

Fig. 5 is a view showing a state at the start of mold opening of the linear motor of the third embodiment (when the mold closing is completed). The direction of the arrow in Fig. 5 indicates the mold opening direction.

The linear motor 228 shown in Fig. 5 drives the mold opening and closing operation in place of the linear motor 28 shown in Fig. 3 . The linear motor 228 is a 3-phase AC type motor and is composed of a fixing member 229 and a movable member 231.

The fixing member 229 includes a fixing portion 230 and a plurality of permanent magnets 232A and 232B which are provided in the fixing portion 230 and are arranged at intervals in a direction parallel to the opening and closing direction of the mold. The plurality of permanent magnets 232A, 232B are arranged at equal intervals Pm, and the magnetic poles on the side of the movable member 231 are alternately magnetized by the N pole and the S pole. The magnetization directions of the permanent magnets 232A and 232B are parallel to the axial direction of the coil 235 of the mover 231. For example, a rare earth magnet is used as the permanent magnets 232A and 232B.

The movable member 231 includes a comb-shaped magnetic core 234 and a plurality of coils 235 wound by a concentrated winding (fractional slot winding) on a plurality of magnetic pole teeth 233 formed on the magnetic core 234. The magnetic pole teeth 233 protrude toward the fixing member 229. a plurality of coils 235 are parallel to the mold opening and closing direction at equal intervals Pt Arrange in the direction. The coil pitch Pt is smaller than the magnet pitch Pm (for example, the case of 8 poles and 9 slots shown in Fig. 5, Pt = 8/9 × Pm).

The plurality of coils 235 are arranged in a direction parallel to the opening and closing direction of the mold, and the phases are arranged separately. For example, as shown in FIG. 3, the order of the three U-phase coils 235, the three V-phase coils 235, and the three W-phase coils 235 is as follows. arrangement.

When the three-phase alternating current is supplied to the plurality of coils 235 at the start of mold opening, the mover 231 starts moving backward from the front end of the stroke. After the movable member 231 is accelerated to the set speed, it is moved rearward at the set speed, and then decelerated and stopped at the rear end of the stroke.

On the other hand, when the three-phase alternating current is supplied to the plurality of coils 235 at the start of mold closing, the mover 231 moves forward from the rear end of the stroke. After the movable member 231 is accelerated to the set speed, it moves forward at the set speed, then decelerates and stops at the leading end of the stroke. At this time, the fixed mold 15 abuts against the movable mold 16.

At the start of mold opening and at the start of mold closing, the waveform of the current flowing to each coil 235 is adjusted to reverse the moving direction of the movable member 231.

In the present embodiment, at least a portion of the movable member 231 (for example, a portion of the W-phase coil 235) is activated in a predetermined direction (for example, a mold opening direction), and the permanent magnet 232A having a thick thickness in the magnetization direction is at the highest speed. When traveling in a predetermined direction (for example, a mold opening direction), the permanent magnet 232B having a low residual magnetic flux density is approached. The permanent magnet 232A having a thick magnetization direction may be partially disposed near one end (for example, the front end) of the stroke of the movable member 231, and the permanent magnet 232B having a thin thickness in the magnetization direction may be disposed in other regions.

When the size G of the air gap 236 formed between the fixing member 229 and the movable member 231 is uniform, and the residual magnetic flux density of the permanent magnet is the same, the thickness of the magnetization direction of the permanent magnet becomes thicker, and the magnetic circuit of the permanent magnet The magnetic permeability coefficient increases. As a result, since the operating point is increased, the average magnetic flux density of the magnetic field generated by the permanent magnets in the air gap 236 (specifically, within a range of ±1/2 Pm from the center of each permanent magnet) becomes strong.

Therefore, in the present embodiment, as in the first embodiment, the magnetic flux density of the magnetic field formed in the air gap 236 by the permanent magnet which is close to at least a part of the movable member 231 (for example, a part of the W-phase coil 235) is also obtained. It is higher when starting in a predetermined direction than when traveling in a predetermined direction at the highest speed.

When the current value of the current flowing through the coil 235 is the same, the magnetic flux density generated in the air gap 236 by the permanent magnet becomes higher, and the torque is increased, so that the movable member 231 is oriented in a predetermined direction (for example, the mold is opened). Direction) can get a large thrust when starting. Therefore, at the start of the mold delivery (for example, at the start of mold opening), a large thrust can be obtained and the performance of the linear motor 228 can be improved, so that it is not necessary to increase the size of the linear motor 228.

When the magnetic flux density generated in the air gap 236 by the permanent magnet becomes high, the induced voltage constant becomes high, but when the movable member 231 is started, the speed of the movable member 231 is slow, and the change in the magnetic flux passing through the coil 235 is small, so The actual induced voltage is small. Since the induced voltage is small, large output of a power source for flowing a current of a desired current value through the coil 235 becomes unnecessary.

When the movable member 231 travels at the highest speed, the magnetic flux density generated in the air gap 236 by the permanent magnet becomes low, so that the induced voltage constant becomes low, and the increase in the induced voltage actually generated is suppressed. Therefore, large output of a power source for flowing a current of a desired current value through the coil 235 becomes unnecessary.

In this manner, the magnetic flux density generated in the air gap 236 is adjusted corresponding to the position of the movable member 231, whereby a large thrust can be obtained when the movable member 231 is started in a predetermined direction, and the restriction of the output voltage of the power source is alleviated. This effect is more remarkable when the permanent magnet 232A having a thick thickness in the magnetization direction is partially disposed near one end (and/or both ends) of the stroke of the movable member 231.

When the movable member 231 is started in a predetermined direction, if the portion where the thrust contribution rate is high, that is, the magnetic flux concentration portion (for example, the W-phase coil 235) is close to the permanent magnet 232A having a thick thickness in the magnetization direction, it is possible to obtain a larger current with less current. The thrust is better and more efficient. The portion where the thrust contribution rate is low (for example, the U-phase and V-phase coil 235) can always approach the permanent magnet 232B having a thin thickness in the magnetization direction regardless of the position of the movable member 231.

As shown in Fig. 5, when the movable member 231 is started in a predetermined direction, a portion having a higher thrust contribution rate (for example, the W-phase coil 235) can be disposed in a portion having a lower thrust contribution ratio (for example, U-phase and V-phase). The coil 235) is on the opposite side to the predetermined direction.

Further, when the movable member 231 is started in a predetermined direction, a portion having a high thrust contribution rate (for example, the V-phase coil 235) can be used as a reference, and a portion having a lower thrust contribution rate (for example, a W phase) on the side opposite to the predetermined direction can be used. line Circle 235). At this time, the portion where the thrust contribution rate is low (for example, the W-phase coil 235) can approach the permanent magnet 232A having a thick thickness in the magnetization direction when the movable member 231 is started in a predetermined direction. The permanent magnets 232A having a thicker base in the magnetization direction are continuously arranged on the side opposite to the predetermined direction (for example, the mold opening direction) of the permanent magnets 232B having a thinner thickness in the magnetization direction. Therefore, when the permanent magnet 232A having a thick magnetization direction is disposed between the permanent magnets 232B having a small thickness in the magnetization direction, the pulsation of the torque is suppressed when the movable member 231 is started.

Further, in the present embodiment, as shown in Fig. 5, the permanent magnet 232A having a thick magnetization direction is partially disposed near the end of the stroke of the movable member 231, but when the upper limit value of the output voltage of the power source is high, It is formed over a range greater than or equal to the length of the movable member 231.

The first embodiment to the third embodiment of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and various modifications and changes can be made within the scope of the invention as described in the claims.

For example, the first embodiment to the third embodiment are applied to the case where the movable member is started in the mold opening direction, but the moving direction of the movable member is not limited to the mold opening direction. The moving direction of the movable member can also be the closed mold direction. In addition, the present invention can also be applied to mold opening and mold closing.

Further, in the first to third embodiments, at least one of (1) a permanent magnet having a different residual magnetic flux, (2) an air gap of a different size, and (3) a permanent magnet having a different magnetization direction thickness is used. The invention may also use any two of (1) to (3) in combination or 3 items.

28‧‧‧Line motor

29‧‧‧Fixed parts

30‧‧‧ Fixed Department

31‧‧‧ movable parts

32A‧‧‧ permanent magnet

32B‧‧‧ permanent magnet

33‧‧‧Magnetic teeth

34‧‧‧ magnetic core

35‧‧‧ coil

36‧‧‧Air gap

H‧‧‧Magnetization direction thickness H of permanent magnet

G‧‧‧Air gap size

Pm‧‧‧Magnet spacing

Pt‧‧‧Coil spacing

Claims (6)

An injection molding machine comprising a three-phase AC type linear motor for driving a mold opening and closing operation, wherein the linear motor includes a movable member including a plurality of coils arranged at intervals in a direction parallel to a mold opening and closing direction. And a fixing member comprising a plurality of permanent magnets arranged at intervals in a direction parallel to the opening and closing direction of the mold, and an air gap is formed between the fixing member and the movable member, wherein at least one of the movable members is formed The magnetic flux density of the magnetic field formed in the air gap by the portion of the permanent magnet that is close to each other is higher when the movable member is started in the predetermined direction than when the movable member travels in the predetermined direction at the highest speed. The injection molding machine according to claim 1, wherein a residual magnetic flux density of the permanent magnet adjacent to at least a portion of the movable member is higher than the movable member when the movable member is activated in the predetermined direction. The highest speed is higher when walking in the aforementioned predetermined direction. The injection molding machine according to claim 1 or 2, wherein an air gap formed between at least a portion of the movable member and the fixing member is started when the movable member is started in the predetermined direction. It is narrower than when the movable member is traveling at the highest speed in the aforementioned predetermined direction. The injection molding machine according to any one of the preceding claims, wherein The thickness of the magnetization direction of the permanent magnet approached by at least a portion of the movable member is thicker when the movable member is started in the predetermined direction than when the movable member travels in the predetermined direction at the highest speed. The injection molding machine according to any one of claims 1 to 4, wherein the magnetic flux density in the air gap is generated by the respective permanent magnets of the fixing member at one end of the stroke of the movable member Partially high near and/or near the ends. The injection molding machine according to any one of the preceding claims, wherein the magnetic flux density of the magnetic field formed in the air gap by the permanent magnet approaching at least a portion of the movable member When the movable member is started in a direction opposite to the predetermined direction, the movable member is higher than the movable member at a maximum speed in a direction opposite to the predetermined direction.