JP5829153B2 - Injection molding machine - Google Patents

Description

  The present invention relates to an injection molding machine.

  An injection molding machine manufactures a molded product by filling molten resin into a cavity space of a mold apparatus and solidifying the resin. The mold apparatus includes a fixed mold and a movable mold, and a cavity space is formed between the fixed mold and the movable mold when the mold is clamped. Mold closing, mold clamping, and mold opening of the mold apparatus are performed by a mold clamping apparatus. As a mold clamping device, there has been proposed a mold clamping device that uses a linear motor for mold opening and closing operations and uses an attractive force of an electromagnet for mold clamping operations (see, for example, Patent Document 1).

International Publication No. 2005/090052

Improvement of the performance of the linear motor at the start of mold feeding is desired. For example, at the start of mold opening, the frictional resistance between the positioning pin formed on one of the fixed mold and the movable mold pin and the pin hole formed on the other, the adhesive force due to the resin between the fixed mold and the movable mold, Since the mold opening operation is performed against the attracting force or the like due to the residual magnetic flux of the electromagnet, an improvement in driving force is required. Larger linear motors are effective for improving the driving force, but the installation space for linear motors is limited as the injection molding machine becomes more compact.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide an injection molding machine that can suppress an increase in the size of the linear motor and can improve the performance of the linear motor at the start of mold feeding.

In order to solve the above problems, an injection molding machine according to an aspect of the present invention is provided.
In an injection molding machine equipped with a three-phase AC type linear motor that drives a mold opening and closing operation,
The linear motor includes a mover including a plurality of coils arranged at intervals in a direction parallel to the mold opening / closing direction and a stator including a plurality of permanent magnets arranged at intervals in a direction parallel to the mold opening / closing direction. An air gap is formed between the stator and the mover,
The magnetic flux density of the magnetic field formed in the air gap by the permanent magnet with which at least a part of the mover is in close proximity is the maximum speed of the mover in the predetermined direction when the mover is started in the predetermined direction. rather than higher than that at the time of traveling,
The air gap formed between at least a part of the mover and the stator is greater than when the mover starts in the predetermined direction and travels at the highest speed in the predetermined direction. Is too narrow.

  ADVANTAGE OF THE INVENTION According to this invention, while being able to suppress the enlargement of a linear motor, the injection molding machine which can improve the performance of the linear motor at the time of a mold feed start is provided.

The figure which shows the state at the time of the mold opening start (at the time of completion | finish of mold closing) of the injection molding machine by 1st Embodiment of this invention. The figure which shows the state at the time of the mold closing start (at the time of completion | finish of mold opening) of the injection molding machine by 1st Embodiment of this invention. The figure which shows the state at the time of the mold opening start (at the time of completion | finish of mold closing) of the linear motor by 1st Embodiment. The figure which shows the state at the time of the mold opening start (at the time of completion | finish of mold closing) of the linear motor by 2nd Embodiment. The figure which shows the state at the time of the mold opening start of the linear motor by 3rd Embodiment (at the time of completion | finish of mold closing)

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In each of the drawings, the same or corresponding components are denoted by the same or corresponding reference numerals, and description thereof will be omitted. Further, a description will be given assuming that the moving direction of the movable platen when performing mold closing is the front and the moving direction of the movable platen when performing mold opening is the rear.

[First Embodiment]
FIG. 1 is a diagram showing a state at the start of mold opening (at the end of mold closing) of the injection molding machine according to the first embodiment of the present invention. FIG. 2 is a diagram showing a state at the start of mold closing (at the end of mold opening) of the injection molding machine according to the first embodiment of the present invention. In FIG.1 and FIG.2, illustration of some of the some coils contained in a linear motor is abbreviate | 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 may be provided on a position adjustment base Ba that is movable along a guide Gd that extends in the mold opening / closing direction (left-right direction in the drawing). The fixed platen 11 may be placed on the frame Fr.

  A movable platen 12 is disposed facing the fixed platen 11. The movable platen 12 is fixed on the movable base Bb, and the movable base Bb can run on the guide Gd. Thereby, the movable platen 12 is movable in the mold opening / closing direction with respect to the fixed platen 11.

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

  Between the fixed platen 11 and the rear platen 13, four tie bars 14 (only two of the four tie bars 14 are shown in the figure) are installed as connecting members. The fixed platen 11 is fixed to the rear platen 13 via the tie bar 14. A movable platen 12 is disposed along the tie bar 14 so as to freely advance and retract. A guide hole (not shown) for penetrating the tie bar 14 is formed at a position corresponding to the tie bar 14 in the movable platen 12. In addition, you may make it form a notch part instead of a guide hole.

  A screw portion (not shown) is formed at the front end portion (right end portion in the drawing) of the tie bar 14, and the front end portion of the tie bar 14 is fixed to the fixed platen 11 by screwing and tightening a nut n1 to the screw portion. The rear end of the tie bar 14 is fixed to the rear platen 13.

  A fixed mold 15 is attached to the fixed platen 11, and a movable mold 16 is attached to the movable platen 12. The fixed mold 15 and the movable mold 16 are brought into contact with and separated from each other as the movable platen 12 advances and retreats. Closing, mold clamping and mold opening are performed. 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 cavity space is filled with molten resin. A mold apparatus 19 is configured by the fixed mold 15 and the movable mold 16.

  The suction plate 22 is disposed in parallel with the movable platen 12. The suction plate 22 is fixed to the slide base Sb via the mounting plate 27, and the slide base Sb can travel on the guide Gd. As a result, the suction plate 22 can move back and forth behind the rear platen 13. The suction plate 22 may be formed of a magnetic material. The attachment plate 27 may not be provided, and in this case, the suction plate 22 is directly fixed to the slide base Sb.

  The rod 39 is connected to the suction plate 22 at the rear end portion and is connected to the movable platen 12 at the front end portion. Therefore, the rod 39 is moved forward as the suction plate 22 moves forward when the mold is closed to move the movable platen 12 forward, and is retracted and moved backward as the suction plate 22 moves back when the mold is opened. Retreat. For this purpose, a rod hole 41 for penetrating the rod 39 is formed in the central portion of the rear platen 13.

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

  The linear motor 28 is a so-called moving coil type three-phase synchronous motor, and includes a stator 29 including a plurality of permanent magnets 32 </ b> A and 32 </ b> B (see FIG. 3) and a mover 31 including a plurality of coils 35. The stator 29 is fixed on the frame Fr and is formed corresponding to the moving range of the slide base Sb. The mover 31 is fixed to the slide base Sb, is opposed to the stator 29, and is formed over a predetermined range. The position of the mover 31 is detected by the position sensor 53.

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

  The electromagnet unit 37 generates an attracting force between the rear platen 13 and the attracting 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 includes an electromagnet 49 formed on the rear platen 13 side and a suction portion 51 formed on the suction plate 22 side. The suction portion 51 is formed in a predetermined portion of the suction surface (front end surface) of the suction plate 22, for example, a portion surrounding the rod 39 in the suction plate 22 and facing the electromagnet 49. A groove 45 for accommodating the coil 48 of the electromagnet 49 is formed around a predetermined portion of the attracting surface (rear end surface) of the rear platen 13, for example, around the rod 39. A core 46 is formed inside the groove 45. A coil 48 is wound around the core 46. A yoke 47 is formed at a portion other than the core 46 of the rear platen 13.

  In the present embodiment, the electromagnet 49 is formed separately from the rear platen 13 and the attracting part 51 is formed separately from the attracting plate 22, but the electromagnet is part of the rear platen 13 and the attracting part is part of the attracting plate 22. May be formed. Moreover, the arrangement of the electromagnet and the attracting part may be reversed. For example, the electromagnet 49 may be provided on the suction plate 22 side, and the suction portion 51 may be provided on the rear platen 13 side. Moreover, the number of the coils 48 of the electromagnet 49 may be plural.

  When an electric current is supplied to the coil 48 in the electromagnet unit 37, the electromagnet 49 is driven to attract the attracting part 51 and generate a mold clamping force. The electromagnet 49 is feedback-controlled based on the detection result of the mold clamping force sensor 55 that detects the mold clamping force so that the mold clamping force becomes a target value. The mold clamping force sensor 55 is composed of, for example, a strain sensor that detects distortion (elongation amount) of the tie bar 14 that expands according to the mold clamping force. The strain sensor is installed on at least one tie bar 14.

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

  Next, the operation of the injection molding machine 10 configured as described above will be described. Various operations of the injection molding machine 10 are performed under the control of the control unit 60.

  The controller 60 controls the mold closing process. The controller 60 supplies the current to the coil 35 of the linear motor 28 in the state shown in FIG. 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 suction plate 22, that is, between the electromagnet 49 and the suction portion 51. Note that the force required for mold closing is sufficiently reduced compared to the mold clamping force.

  Subsequently, the control unit 60 controls the mold clamping process. The controller 60 supplies current to the coil 48 of the electromagnet 49 and attracts the attracting part 51 to the electromagnet 49. 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. Molten resin is filled in the cavity space of the mold apparatus 19 in the mold-clamping state. When the resin is cooled and solidified, the controller 60 cuts off the power supply 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 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 moved backward to perform mold opening. After the mold opening, the molded product is taken out from the movable mold 16.

  Next, the configuration of the linear motor 28 will be described in detail with reference to FIG. FIG. 3 is a diagram illustrating a state of the linear motor according to the first embodiment at the time of mold opening start (at the time of mold closing end). In FIG. 3, a permanent magnet having a high residual magnetic flux density is shown in black, and a permanent magnet having a low residual magnetic flux density is shown in white. Moreover, the arrow direction in FIG. 3 represents a mold opening direction.

  The linear motor 28 is a three-phase AC motor and includes a stator 29 and a mover 31.

  The stator 29 includes a fixed portion 30 and a plurality of permanent magnets 32A and 32B that are provided on the fixed portion 30 and are arranged at intervals in a direction parallel to the mold opening / closing direction. The plurality of permanent magnets 32A and 32B are arranged at an equal pitch Pm, and the magnetic poles on the side of the mover 31 are alternately magnetized into N and S poles. 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, rare earth magnets are used as the permanent magnets 32A and 32B.

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

  The plurality of coils 35 are arranged for each phase along a direction parallel to the mold opening / closing direction, and a plurality (three in FIG. 3) of U-phase coils 35 and a plurality (three in FIG. 3) of V-phases. Coils 35 and a plurality (three in FIG. 3) of W-phase coils 35 are arranged in this order.

  When a three-phase alternating current is supplied to the plurality of coils 35 at the start of mold opening, the mover 31 starts to move backward from the front end of the stroke. The mover 31 is accelerated to the set speed, then moves backward at the set speed, then decelerated, and stops at the rear end of the stroke.

  On the other hand, when a three-phase alternating current is supplied to the plurality of coils 35 at the start of mold closing, the mover 31 starts moving forward from the rear end of the stroke. The mover 31 is accelerated to the set speed, then moves forward at the set speed, then decelerated, and stops at the front end of the stroke. At this time, the fixed mold 15 and the movable mold 16 come into contact with each other.

  The waveform of the current flowing through each coil 35 is adjusted so that the moving direction of the mover 31 is reversed between the start of mold opening and the start of mold closing.

  In the present embodiment, at least a part of the mover 31 (for example, the part of the W-phase coil 35) is close to the permanent magnet 32A having a high residual magnetic flux density when starting in a predetermined direction (for example, the mold opening direction), When traveling at the highest speed in the direction (for example, the mold opening direction), it approaches the permanent magnet 32B having a low residual magnetic flux density. Here, that a specific coil is close to a specific permanent magnet means that the specific permanent magnet is within a range of ± 1/2 × Pt in the direction parallel to the mold opening / closing direction around the central axis of the specific coil. Means there is at least some. The permanent magnet 32A having a high residual magnetic flux density may be locally arranged near one end (for example, the front end) of the stroke of the mover 31, and the permanent magnet 32B having a low residual magnetic flux density may be arranged in other regions.

  The residual magnetic flux density is determined by, for example, the type and purity of the rare earth element that is the material of the permanent magnets 32A and 32B. For example, the residual magnetic flux density of a neodymium magnet is higher than the residual magnetic flux density of a samarium cobalt magnet. Further, even with the same neodymium magnet, the residual magnetic flux density increases as the sintering aid is less and the purity is higher.

  When the dimension G of the air gap 36 formed between the stator 29 and the mover 31 is the same and the magnetization direction thickness H of the permanent magnet is the same, the higher the residual magnetic flux density of the permanent magnet, the more air is introduced by each permanent magnet. The magnetic flux density of the magnetic field generated in the gap 36 (specifically, within a range of ± 1/2 Pm from the center of each permanent magnet) is increased.

  Therefore, the magnetic flux density of the magnetic field formed in the air gap 36 by the permanent magnet with which at least a part of the mover 31 (for example, the part of the W-phase coil 35) is close is the highest in the predetermined direction. Higher than when driving at high speeds.

  When the current value of the current flowing through the coil 35 is the same, the higher the magnetic flux density generated in the air gap 36 by the permanent magnet, the higher the generated torque. Therefore, when the mover 31 starts in a predetermined direction (for example, the mold opening direction) Thrust can be obtained. Accordingly, a large thrust is obtained at the start of mold feeding (for example, at the start of mold opening), and the performance of the linear motor 28 is improved, so that the linear motor 28 does not need to be enlarged.

When the magnetic flux density occurring Eagya-up 36 by the permanent magnet becomes high, but the induced voltage constant becomes high, at the time of start-up of the movable element 31, slow down of the movable element 31, since the change in the magnetic flux penetrating the coil 35 is small, in fact Induced voltage is small. Since the induced voltage is small, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 35.

  When the mover 31 travels at the highest speed, the magnetic flux density generated in the air gap 36 by the permanent magnet is lowered, so that the induced voltage constant is lowered, and an increase in the induced voltage actually generated is suppressed. For this reason, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 35.

  In this way, by adjusting the magnetic flux density generated in the air gap 36 according to the position of the mover 31, a large thrust can be obtained when the mover 31 is started in a predetermined direction, and the restriction on the output voltage of the power source is eased. Is done. In addition, since the permanent magnet 32A having a high residual magnetic flux density is partially used, it is possible to suppress an increase in cost due to high performance of the permanent magnet. These effects are remarkable when the permanent magnet 32A having a high residual magnetic flux density is locally arranged near one end (and / or near both ends) of the stroke of the mover 31.

  By the way, in the concentrated winding linear motor 28, the coil 35 of a specific phase (for example, W phase) among the three-phase coils 35 tends to contribute to the thrust of the mover 31, and the coil having a high thrust contribution ratio. Changes in synchronization with the power supply frequency, and changes according to the position of the mover 31. A phase coil with a high thrust contribution ratio may span two phase coils. The phase coil 35 having a high thrust contribution rate can be determined by the relative positional relationship between the permanent magnets 32A and 32B and the coil 35 at the time of starting, the phase of each phase, and the like, and can be confirmed in advance by simulation. A large thrust is generated at a magnetic flux concentrating portion (a portion where magnetic flux from the stator 29 is concentrated) in the mover 31.

  When the mover 31 is started in a predetermined direction, if a magnetic flux concentrating portion (for example, a W-phase coil 35), which is a portion having a high thrust contribution rate, is in close proximity to the permanent magnet 32A having a high residual magnetic flux density, less current is required. Large thrust is obtained and efficiency is high. Regardless of the position of the mover 31, the portion having a low thrust contribution rate (for example, U-phase and V-phase coils) may always be close to the permanent magnet 32 </ b> B having a low residual magnetic flux density.

  When the mover 31 is started in a predetermined direction, a portion with a high thrust contribution rate (for example, the W-phase coil 35) is a portion with a low thrust contribution rate (for example, the U-phase and V-phase coils 35), as shown in FIG. ) Than the predetermined direction.

When the mover 31 is started in a predetermined direction, a portion having a high thrust contribution rate (for example, a V-phase coil 35) and a portion having a low thrust contribution rate on the opposite side of the predetermined direction (for example, a W-phase coil 35) is used. There may be. In this case, the portion having a low thrust contribution rate (for example, the W-phase coil 35) may be close to the permanent magnet 32A having a high residual magnetic flux density when the mover 31 is started in a predetermined direction. The permanent magnet 32A having a high residual magnetic flux density is continuously arranged on a side opposite to a predetermined direction (for example, the mold opening direction) from the permanent magnet 32B having a low residual magnetic flux density. Therefore, compared with the case where 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, torque pulsation is suppressed when the mover 31 moves.

  In the present embodiment, the permanent magnet 32A having a high residual magnetic flux density is disposed locally near one end of the stroke of the mover 31 as shown in FIG. 3, for example, but the upper limit value of the output voltage of the power source is When it is high, it may be arranged over a range equal to or greater than the length of the mover 31.

[Second Embodiment]
FIG. 4 is a diagram showing a state of the linear motor according to the second embodiment at the time of mold opening start (at the time of mold closing end). In FIG. 4, the arrow direction represents the mold opening direction.

  A linear motor 128 shown in FIG. 4 drives a mold opening / closing operation instead of the linear motor 28 shown in FIG. The linear motor 128 is a three-phase AC motor and includes a stator 129 and a mover 131.

  The stator 129 includes a fixed portion 130 and a plurality of permanent magnets 132A and 132B that are provided on the fixed portion 130 and are arranged at intervals in a direction parallel to the mold opening / closing direction. The plurality of permanent magnets 132A and 132B are arranged at an equal pitch Pm, and the magnetic poles on the side of the movable element 131 are alternately magnetized into N and S poles. 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, rare earth magnets are used as the permanent magnets 132A and 132B.

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

  The plurality of coils 135 are arranged in each phase along a direction parallel to the mold opening / closing direction. For example, as shown in FIG. 3, three U-phase coils 135, three V-phase coils 135, and 3 Two W-phase coils 135 are arranged in this order.

  When a three-phase alternating current is supplied to the plurality of coils 135 at the start of mold opening, the mover 131 starts moving from the front end of the stroke toward the rear. The mover 131 is accelerated to the set speed, then moves backward at the set speed, is then decelerated, and stops at the rear end of the stroke.

  On the other hand, when a three-phase alternating current is supplied to the plurality of coils 135 at the start of mold closing, the mover 131 starts to move forward from the rear end of the stroke. The mover 131 is accelerated to the set speed, then moves forward at the set speed, then decelerated, and stops at the front end of the stroke. At this time, the fixed mold 15 and the movable mold 16 come into contact with each other.

  The waveform of the current flowing through each coil 135 is adjusted so that the moving direction of the mover 131 is reversed between the start of mold opening and the start of mold closing.

In the present embodiment, at least a part of the mover 131 (for example, a part of the W-phase coil 135) forms a narrow air gap 136A with the stator 129 at the time of starting in a predetermined direction (for example, the mold opening direction). A wide air gap 136B is formed between the stator 129 and the stator 129 when traveling at a maximum speed in a predetermined direction (for example, a mold opening direction). And Eagya-up 136A, step portion corresponding to the dimensional difference between the air gap 136B is, the permanent magnet 132A of the fixed portion 130, are formed on the surface 132B is fixed. The narrow air gap 136A may be locally formed near one end (for example, the front end) of the stroke of the movable element 131, and the wide air gap 136B may be formed in other regions.

  When the permanent magnets 132A and 132B have the same residual magnetic flux density and the permanent magnets 132A and 132B have the same magnetization direction thickness H, the air gaps (in detail, the permanent magnets are more specifically described) as the air gap becomes narrower. The magnetic flux density of the magnetic field generated within the range of ± 1/2 Pm from the center of 132A and 132B is increased.

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

  When the current value of the current flowing through the coil 135 is the same, the higher the magnetic flux density generated in the air gap by the permanent magnet, the higher the generated torque, so that a large thrust is generated when the mover 131 is started in a predetermined direction (for example, the mold opening direction). Is obtained. Therefore, a large thrust is obtained at the start of mold feeding (for example, at the start of mold opening), and the performance of the linear motor 128 is improved, so that the linear motor 128 need not be enlarged.

When the magnetic flux density occurring Eagya-up by the permanent magnet becomes high, but the induced voltage constant becomes high, at the time of start-up of the movable element 131, slow down of the movable element 131, the change in magnetic flux penetrating the coil 135 is small, actually The induced voltage generated is small. Since the induced voltage is small, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 135.

When running at the maximum speed of the movable element 131, the magnetic flux density occurring Eagya-up by the permanent magnets becomes lower, the induced voltage constant becomes low, the actual increase of the induced voltage generated is suppressed. For this reason, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 135.

  Thus, by adjusting the magnetic flux density generated in the air gaps 136A and 136B according to the position of the mover 131, a large thrust can be obtained when the mover 131 is started in a predetermined direction, and the output voltage of the power supply is restricted. Is alleviated. This effect is remarkable when the narrow air gap 136A is locally formed near one end (and / or near both ends) of the stroke of the movable element 131.

  A narrow air gap between the stator 129 and the magnetic pole teeth 133 around which a magnetic flux concentrating portion (for example, a W-phase coil 135) having a high thrust contribution ratio is wound when the movable element 131 is started in a predetermined direction. When 136A is formed, a large thrust can be obtained with a smaller current, and the efficiency is good. Regardless of the position of the mover 131, the magnetic pole teeth 133 around which the portion with a low thrust contribution rate (for example, the U-phase and V-phase coils 135) is wound always has a wide air gap 136B. It may be formed.

  When the mover 131 is started in a predetermined direction, a portion with a high thrust contribution rate (for example, the W-phase coil 135) is a portion with a low thrust contribution rate (for example, the U-phase and V-phase coils 135), as shown in FIG. ) Than the predetermined direction.

When the movable element 131 is started in a predetermined direction, a portion with a low thrust contribution rate (for example, a W-phase coil 135) on the side opposite to the predetermined direction with a portion having a high thrust contribution rate (for example, a V-phase coil 135) as a reference. There may be. In this case, a narrow air gap 136A is formed between the magnetic pole teeth 133 around which the portion having a low thrust contribution rate (for example, the W-phase coil 135) is wound and the stator 129 when the mover 131 starts in a predetermined direction. May be formed. The narrow air gap 136A is continuously formed on the side opposite to the predetermined direction (for example, the mold opening direction) from the wide air gap 136B. Therefore, as compared with the case where a narrow Eagya-up 136A is sandwiched between the wide air gap 136B, upon movement of the movable element 131, the pulsation of the torque is suppressed.

  In the present embodiment, the narrow air gap 136A is locally formed near one end of the stroke of the mover 131 as shown in FIG. 3, for example. However, if the upper limit value of the output voltage of the power source is high, the narrow air gap 136A is movable. It may be formed over a range equal to or greater than the length of the child 131.

  In the present embodiment, the step portion is formed on the surface of the fixed portion 130 on which the permanent magnets 132A and 132B are fixed, but the surface may be planar. In this case, permanent magnets having different magnetization direction thicknesses corresponding to the dimensional difference between the narrow air gap 136A and the wide air gap 136B are used. In this case, the processing cost of the fixed portion 130 is reduced, and the details will be described in the third embodiment. However, an injection molding machine at the start of mold feeding is provided by locally arranging permanent magnets having a large magnetization direction thickness. The performance is further improved.

[Third Embodiment]
FIG. 5 is a diagram illustrating a state of the linear motor according to the third embodiment when the mold opening is started (when the mold closing is completed). In FIG. 5, the arrow direction represents the mold opening direction.

  A linear motor 228 shown in FIG. 5 drives a mold opening / closing operation instead of the linear motor 28 shown in FIG. The linear motor 228 is a three-phase AC motor and includes a stator 229 and a mover 231.

  The stator 229 includes a fixed portion 230 and a plurality of permanent magnets 232A and 232B that are provided in the fixed portion 230 and are arranged at intervals in a direction parallel to the mold opening / closing direction. The plurality of permanent magnets 232A and 232B are arranged at an equal pitch Pm, and the magnetic pole on the side of the mover 231 is alternately magnetized into an N pole and an 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, rare earth magnets are used as the permanent magnets 232A and 232B.

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

  The plurality of coils 235 are arranged for each phase along a direction parallel to the mold opening / closing direction. For example, as shown in FIG. 3, three U-phase coils 235, three V-phase coils 235, and 3 Two W-phase coils 235 are arranged in this order.

  When a three-phase alternating current is supplied to the plurality of coils 235 at the start of mold opening, the mover 231 starts moving from the front end of the stroke toward the rear. The mover 231 is accelerated to the set speed, then moves rearward at the set speed, then decelerated, 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 235 at the start of mold closing, the mover 231 starts to move forward from the rear end of the stroke. The mover 231 is accelerated to the set speed, then moves forward at the set speed, then decelerated, and stops at the front end of the stroke. At this time, the fixed mold 15 and the movable mold 16 come into contact with each other.

  The waveform of the current passed through each coil 235 is adjusted so that the moving direction of the mover 231 is reversed between the start of mold opening and the start of mold closing.

  In the present embodiment, at least a part of the mover 231 (for example, the part of the W-phase coil 235) is close to the permanent magnet 232A having a thick magnetization direction at the time of starting in a predetermined direction (for example, the mold opening direction). When traveling at the highest speed in the direction (for example, the mold opening direction), the permanent magnet 232B comes close to the thin magnetized direction. The permanent magnet 232A having a large magnetization direction thickness may be locally disposed near one end (for example, the front end) of the stroke of the mover 231, and the permanent magnet 232B having a small magnetization direction thickness may be disposed in the other region.

  When the dimension G of the air gap 236 formed between the stator 229 and the mover 231 is uniform and the residual magnetic flux density of the permanent magnet is the same, the thicker the magnetization direction thickness of the permanent magnet, the larger the magnetic circuit of the permanent magnet. Increases permeance coefficient. As a result, the operating point is increased, and the average magnetic flux density of the magnetic field generated by each permanent magnet in the air gap 236 (specifically, within a range of ± 1/2 Pm from the center of each permanent magnet) is increased.

  Therefore, also 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 to which at least a part of the mover 231 (for example, the part of the W-phase coil 235) is close. However, when starting in a predetermined direction, it is higher than when traveling at the highest speed in a predetermined direction.

  When the current value of the current flowing through the coil 235 is the same, the higher the magnetic flux density generated in the air gap 236 by the permanent magnet, the higher the generated torque increases. Therefore, when the mover 231 starts in a predetermined direction (for example, the mold opening direction) Thrust can be obtained. Accordingly, a large thrust is obtained at the start of mold feeding (for example, at the start of mold opening), and the performance of the linear motor 228 is improved, so that the linear motor 228 need not be enlarged.

When the magnetic flux density occurring Eagya-up 236 by the permanent magnet becomes high, but the induced voltage constant becomes high, at the time of start-up of the movable element 231, the speed of the movable element 231 is slow, the change in magnetic flux penetrating the coil 235 is small, in fact Induced voltage is small. Since the induced voltage is small, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 235.

  When the mover 231 travels at the highest speed, the magnetic flux density generated in the air gap 236 by the permanent magnet is lowered, so that the induced voltage constant is lowered, and an increase in the induced voltage actually generated is suppressed. For this reason, it is not necessary to increase the output of the power source for flowing a current having a desired current value to the coil 235.

  Thus, by adjusting the magnetic flux density generated in the air gap 236 according to the position of the mover 231, a large thrust can be obtained when the mover 231 is started in a predetermined direction, and the restriction on the output voltage of the power source is relaxed. Is done. This effect is significant when the permanent magnet 232A having a large magnetization direction thickness is locally disposed near one end (and / or near both ends) of the stroke of the mover 231.

  When the mover 231 is started in a predetermined direction, if the magnetic flux concentrating portion (for example, the W-phase coil 235), which is a portion having a high thrust contribution ratio, is in proximity to the permanent magnet 232A having a large thickness in the magnetization direction, less current is required. Can produce a large thrust and is efficient. A portion with a low thrust contribution ratio (for example, the U-phase and V-phase coils 235) may always be close to the permanent magnet 232B having a small thickness in the magnetization direction regardless of the position of the mover 231.

  When the mover 231 is started in a predetermined direction, a portion with a high thrust contribution rate (for example, the W-phase coil 235) is a portion with a low thrust contribution rate (for example, the U-phase and V-phase coils 235 as shown in FIG. 5). ) Than the predetermined direction.

  When the mover 231 is started in a predetermined direction, a portion having a high thrust contribution rate (for example, a V-phase coil 235) is used as a reference and a portion having a low thrust contribution rate (for example, a W-phase coil 235) on the opposite side of the predetermined direction. There may be. In this case, the portion having a low thrust contribution rate (for example, the W-phase coil 235) may be close to the permanent magnet 232A having a large magnetization direction thickness when the mover 231 is started in a predetermined direction. The permanent magnets 232A having a large magnetization direction thickness are continuously arranged on the side opposite to the predetermined direction (for example, the mold opening direction) more than the permanent magnet 232B having a small magnetization direction thickness. Therefore, compared with the case where the permanent magnet 232A having a large magnetization direction thickness is disposed between the permanent magnets 232B having a small magnetization direction thickness, torque pulsation is suppressed when the mover 231 is started.

  In this embodiment, the permanent magnet 232A having a large magnetization direction thickness is locally disposed near one end of the stroke of the mover 231 as shown in FIG. 5, for example, but the upper limit value of the output voltage of the power source is When it is high, it may be arranged over a range equal to or greater than the length of the mover 231.

  As mentioned above, although 1st Embodiment-3rd Embodiment of this invention was described, this invention is not limited to the said embodiment, In the range of the summary of this invention described in the claim, Various modifications and changes are possible.

  For example, although the said 1st Embodiment-3rd Embodiment are applied at the time of the start to a mold open direction of a needle | mover, the moving direction of a needle | mover is not limited to a mold open direction. The moving direction of the mover may be the mold closing direction. Further, the present invention may be applied to both mold opening and mold closing.

  In the first to third embodiments, any one of (1) a permanent magnet having a different residual magnetic flux density, (2) an air gap having a different size, and (3) a permanent magnet having a different magnetization direction thickness is used. Although used, in the present invention, any two or three of the above (1) to (3) may be used in combination.

DESCRIPTION OF SYMBOLS 10 Injection molding machine 11 Fixed platen 12 Movable platen 13 Rear platen 15 Fixed mold 16 Movable mold 19 Mold apparatus 22 Suction plate 28 Linear motor 29 Stator 30 Fixed part 32A, 32B Permanent magnet 31 Movable element 33 Magnetic pole tooth 34 Core 35 Coil 36 Air gap

Claims (5)

In an injection molding machine equipped with a three-phase AC type linear motor that drives a mold opening and closing operation,
The linear motor includes a mover including a plurality of coils arranged at intervals in a direction parallel to the mold opening / closing direction and a stator including a plurality of permanent magnets arranged at intervals in a direction parallel to the mold opening / closing direction. An air gap is formed between the stator and the mover,
The magnetic flux density of the magnetic field formed in the air gap by the permanent magnet with which at least a part of the mover is in close proximity is the maximum speed of the mover in the predetermined direction when the mover is started in the predetermined direction. rather than higher than that at the time of traveling,
The air gap formed between at least a part of the mover and the stator is greater than when the mover starts in the predetermined direction and travels at the highest speed in the predetermined direction. An injection molding machine characterized by its narrowness .   The residual magnetic flux density of a permanent magnet to which at least a part of the mover is adjacent is higher when the mover starts in the predetermined direction than when the mover travels at the highest speed in the predetermined direction. The injection molding machine according to 1. The magnetization direction thickness of the permanent magnet to which at least a part of the mover is adjacent is thicker when the mover starts in the predetermined direction than when the mover travels at the highest speed in the predetermined direction. The injection molding machine according to 1 or 2 . Density of the magnetic flux generated in the air gap by the permanent magnets of the stator, one end vicinity of the stroke of the mover, and / or according to any one of claims 1 to 3, which is locally high at the both ends Injection molding machine. The magnetic flux density of the magnetic field formed in the air gap by the permanent magnet with which at least a part of the mover is close is opposite to the predetermined direction of the mover when the mover is started in the direction opposite to the predetermined direction. The injection molding machine according to any one of claims 1 to 4 , which is higher than when traveling at a maximum speed in a direction.