JP7507493B2 - How to assemble a linear vibration actuator - Google Patents

Description

The present invention relates to a method for assembling a linear vibration actuator that vibrates a movable element in a linear direction.

Conventionally, thin linear vibration actuators have been widely used as devices that provide vibration functions in mobile devices such as smartphones (see, for example, Patent Document 1).

The linear vibration actuator described in Patent Document 1 has a structure in which a single shaft (8) with both ends supported by the peripheral wall of the housing (2) slidably supports a mover, and is configured to vibrate the mover linearly by passing an AC driving current through a coil (15) arranged near a magnet (5) that is part of the mover. In addition, a structure with a single guide shaft can eliminate the possibility of deterioration of vibration characteristics and generation of unnecessary noise caused by low parallelism between multiple shafts (e.g., two shafts).

When assembling a linear vibration actuator equipped with such a guide shaft, the mover is basically placed inside the housing, and the guide shaft is assembled by passing it from the outside to the inside of the housing through the guide shaft support hole formed in the peripheral wall of the housing and the sliding part of the mover. Therefore, a certain amount of clearance (backlash) is required between the hole in the peripheral wall and the outer diameter of the guide shaft. The positioning of the mover and guide shaft is mainly determined by the positions of the shaft support hole formed on one side of the peripheral wall and the hole formed on the opposing side of the peripheral wall, the diameters of these holes, and the outer diameter of the guide shaft.

JP 2015-95943 A

To suppress rotation around the vibration axis of the mover and achieve stable linear vibration, it is desirable to have two or more guide shafts. However, when arranging multiple guide shafts, the guide shafts must be positioned with high precision to suppress deterioration of vibration characteristics and abnormal noise caused by increased sliding resistance and variation.

The sliding resistance depends on the clearance of the sliding parts (moving element and guide shaft), and the clearance depends on the accumulation of the tolerances of each part. If an attempt is made to reduce the accumulation of tolerances by tightening the tolerances of the hole position and hole diameter in the peripheral wall of the housing that supports both ends of the guide shaft, and the outer diameter of the guide shaft, the guide shaft will be more likely to be damaged.

In addition, the magnet in the mover and the peripheral wall of the housing, which also functions as a yoke, are attracted to each other, making it difficult to pass the shaft through.

In order to solve the above problems, the present invention provides a method for assembling a linear vibration actuator having a movable element that vibrates linearly in a predetermined direction, a number of guide shafts that slidably hold the movable element, and a housing that encloses and houses the movable element and the guide shafts, the method being characterized in that the movable element and the guide shafts are housed in the housing with the guide shafts held in a guide shaft holding portion formed on the movable element, and the guide shafts are fixed so as not to move relative to the peripheral wall portion of the housing.

According to the present invention, it is possible to provide a method for assembling a linear vibration actuator that allows multiple guide shafts to be positioned with high precision and ease. Furthermore, the assembly method of the present invention makes it possible to obtain a linear vibration actuator that has excellent vibration characteristics with stable linear vibration.

1 is a diagram showing a linear vibration actuator according to an embodiment of the present invention. 2A to 2C are diagrams illustrating an assembly method and main parts of the linear vibration actuator. FIG. 4 is a flow diagram of an assembly operation of the linear vibration actuator. 1 is a diagram showing a linear vibration actuator according to an embodiment of the present invention. 2A to 2C are diagrams illustrating an assembly method and main parts of the linear vibration actuator. FIG. 4 is a flow diagram of an assembly operation of the linear vibration actuator. FIG. 1 is a diagram showing a comparative example for a linear vibration actuator according to an embodiment of the present invention. 11A to 11C are diagrams illustrating a method of assembling the linear vibration actuator in the comparative example. FIG. 11 is a flow diagram of an assembly operation for the linear vibration actuator in the comparative example.

The method of assembling a linear vibration actuator of this embodiment includes a movable element that vibrates linearly in a predetermined direction, a plurality of guide shafts that hold the movable element so that the movable element can slide along the predetermined direction, and a housing that encloses and houses the movable element and the guide shafts.The movable element and the guide shafts are housed in the housing with the guide shafts held by a guide shaft holder formed on the movable element, and the guide shafts are fixed so as not to move relative to a peripheral wall of the housing.
According to this configuration, it is possible to provide a method for assembling a linear vibration actuator that allows the arrangement of multiple guide shafts to be performed easily and with high precision. Furthermore, the assembly method of the present invention can provide a linear vibration actuator that has stable linear vibration and excellent vibration characteristics.

Another feature, in addition to the above features, is that, with the guide shaft held by a guide shaft holding portion formed on the mover, intermediate members that constitute a part of the peripheral wall portion of the housing and are arranged on both ends of the guide shaft are fixed to the guide shaft, and then the mover and the guide shaft are housed in the housing, and the intermediate members are fixed to a part of the housing other than the intermediate members.
According to this configuration, the movable element and the guide shafts can be housed within the housing while the parallel relationship between the multiple guide shafts is accurately determined.

Another feature, in addition to the above features, is that grooves for positioning and fixing both ends of the guide shaft are formed on both sides of the peripheral wall of the housing in the direction in which the mover vibrates, and the mover and the guide shaft are housed in the housing by fitting both ends of the guide shaft into the grooves.
According to this configuration, the positioning of the mover and the multiple guide shafts can be easily performed without increasing the number of parts.

Next, a preferred embodiment having the above-mentioned characteristics and a comparative example will be described in detail with reference to the drawings.
In the drawings for explaining each of the examples and comparative examples, the same reference numerals are used for some common components.

1A and 1B are diagrams showing a linear vibration actuator A1 according to this embodiment. Fig. 1A is an external view of the linear vibration actuator A1. In Fig. 1B, the main parts of the exterior are shown by virtual lines to show the internal structure of the linear vibration actuator A1.
FIG. 2 is a diagram for explaining main assembly operations and characteristic component parts of the linear vibration actuator A1 shown in FIG.
FIG. 3 is a flow diagram of the assembly work for the linear vibration actuator A1 shown in FIG.

As shown in Figure 1, the linear vibration actuator A1 vibrates a movable element 20 linearly in a predetermined vibration direction D11, and includes a housing 10, a movable element 20, a guide shaft 30, a flat coil 40, and a pair of magnetic springs 50. In Figure 1(b), the main parts of the housing 10, which corresponds to the exterior, are shown with imaginary lines (thin two-dot chain lines) so that the internal structure of the linear vibration actuator A1 can be seen, and the flexible printed circuit board (FPC) that actually holds the coil 40 and the like are not shown.

The housing 10 is a rectangular box extending in the vibration direction D11 with a length dimension of approximately 20 mm, and at least a portion of the housing 10 is made of a magnetic material. The housing 10 is composed of a peripheral wall portion 11, a bottom wall portion 12, and a ceiling wall portion 13, and an intermediate member 14 is arranged as a part of the peripheral wall portion 11. Each part of the housing 10 is formed by cutting or pressing. A guide shaft 30 and one of the magnets constituting the magnetic spring 50 are fixed to the intermediate member 14. The intermediate member 14 is made of a magnetic material and also functions as a yoke member for the magnet.

The mover 20 is a rectangular parallelepiped member that extends in the vibration direction D11 and is housed in the housing 10, and includes a frame body 21 and a plurality of magnets 22. The magnets 22 are fitted into the frame body 21 in a state where they are linearly arranged in the vibration direction D11. The frame body 21 also has holding portions 21g on both sides along the vibration direction D11 that slidably hold the guide shaft 30.

In this embodiment, there are two guide shafts 30 with an outer diameter of just under φ1 mm, which are fixed to the housing 10 at a specific portion formed in the intermediate member 14 and hold the movable member 20 so that it can slide in the vibration direction D11.

The flat coil 40 is held by a flexible substrate (not shown) and is arranged to face the magnets 22 provided on the movable member 20. When an alternating current is passed through the flat coil 40 as a driving current, the Lorentz force acting between the flat coil 40 and the multiple magnets 22 in the movable member 20 causes the movable member 20 to vibrate linearly in the vibration direction D11.

A pair of magnetic springs 50 are members that urge the movable member 20 in the vibration direction D11 by the repulsive force of magnets, and are arranged at both ends of the movable member 20 in the vibration direction D11. Each magnetic spring 50 has a first biasing magnet 51 and a second biasing magnet 52. The first biasing magnet 51 is arranged at each end of the movable member 20 in the vibration direction D11. The second biasing magnets 52 are arranged inside the housing 10 so as to face each of the first biasing magnets 51. The second biasing magnets 52 have the same polarity as the polarity of the first biasing magnet 51. Each magnetic spring 50 urges the movable member 20 in the vibration direction D11 in a direction away from the inner wall surface of the housing 11 by the repulsive force generated between the first biasing magnet 51 and the second biasing magnet 52 of the same polarity.

The linear vibration actuator A1 has unique components that allow the two guide shafts 30 to be positioned and fixed with high precision. In addition, assembly work can be performed relatively easily. The main assembly work and unique components of the linear vibration actuator A1 are described below with reference to Figure 2.

As shown in Figure 2(a), the guide shaft 30 is assembled into the retaining portion 21g that is formed in advance on the frame body 21 of the mover 20. Next, the intermediate member 14 is prepared. The intermediate member 14 has a hole 14h into which the end of the guide shaft 30 is inserted. The inner diameter of the hole 14h is set appropriately based on the outer diameter of the guide shaft 30 and the press-fit tolerance with the guide shaft 30. The relative positions of the two guide shafts 30 are determined by the hole 14h.

As shown in Figure 2(b), the end of the guide shaft 30 is inserted into the hole 14h of the intermediate member 14 and fixed in place. Next, a housing 10 is prepared in which the peripheral wall 11 and bottom wall 12 are integrated. In a sub-assembly including the mover 20, two guide shafts 30, and two intermediate members 14, the shape and arrangement of the intermediate member 14 are designed to fit snugly against the inner surface of the peripheral wall 11.

As shown in Fig. 2(c), an assembly including the movable member 20, two guide shafts 30, and two intermediate members 14 is placed inside the peripheral wall portion 11. At this time, each of the two intermediate members 14 arranged opposite each other is fixed to the inner peripheral surface of the peripheral wall portion 11 by contacting it on at least three surfaces.

The guide shafts 30 are fixed so as not to move relative to the peripheral wall 11, intermediate member 14, and bottom wall 12 that constitute the housing 10, and the mover 20 is held in a slidable state by the two guide shafts 30. Finally, the flat coil 40 and the like are assembled, and the ceiling wall 13 is attached to complete the linear vibration actuator A1.

Next, the assembly process of the linear vibration actuator A1 will be described in more detail with reference to the flow chart shown in Figure 3. (See Figures 1 and 2 for the reference symbols of each part.)

[1] Preparation of the mover A plurality of magnets 22 are fitted and adhered to the frame 21 of the mover 20. In addition, first biasing magnets 51 constituting the magnetic spring 50 are adhered and fixed to both sides of the frame 21 in the vibration direction.

[2] Mounting the Guide Shafts in the Movable Piece Two guide shafts 30 are mounted in the holders 21 g formed on the frame 21 of the movable piece 20 for slidably holding the guide shafts.

[3] Preparation of Intermediate Members The second biasing magnets 52 constituting the magnetic springs 50 are fixed by adhesive to each of the two intermediate members (yoke members) 14.

[4] Fixing of Guide Shaft and Intermediate Member The end of the guide shaft 13 is press-fitted into the hole 14h formed in the intermediate member 14, and the guide shaft and the intermediate member are fixed together by adhesion or welding.

[5] Preparation of the Housing Side The peripheral wall portion 11 and the bottom wall portion 12 that constitute the housing 10 are integrated together by welding.

[6] Positioning and fixing the mover assembly inside the housing The assembly of the mover 20, guide shaft 30, and intermediate member 14 assembled in the processes [1] to [4] is positioned inside the housing 10 assembled in [5] and fixed.

[7] Fixing the coil/substrate to the ceiling wall of the housing The flat coil 40 and the substrate that holds the flat coil 40 are arranged and fixed to the ceiling wall 13 in advance.

[8] Fixing the Ceiling Wall and the Peripheral Wall of the Housing The ceiling wall 13 constituting the housing 10 is similarly fixed to the peripheral wall 11 by welding, completing the linear vibration actuator A1.

As mentioned above, the work processes [1] to [8] may not necessarily be performed in the order listed, but in this embodiment it is essential that at least the guide shaft 30 is held by the movable member 20 and that the end of the guide shaft is inserted into the hole 14h of the intermediate member (yoke member) 14, and that these are positioned inside the peripheral wall portion 11.

4 is a diagram showing a linear vibration actuator A2 according to this embodiment, in which a part of the ceiling wall 13 constituting the housing 10 is shown in partial cross section in order to show the characteristic parts of this embodiment.
FIG. 5 is a diagram for explaining main assembly operations and characteristic component parts of the linear vibration actuator A2 shown in FIG.
FIG. 6 is a flow chart of the assembly process for the linear vibration actuator A2 shown in FIG.

As shown in FIG. 4, the linear vibration actuator A2 of this embodiment comprises a housing 10, a movable element 20, a guide shaft 30, a flat coil 40, and a pair of magnetic springs 50, and has the same basic configuration for vibrating the movable element 20 in a linear direction as the linear vibration actuator A1 of [Example 1].

The linear vibration actuator A2 of this embodiment is also similar to the linear vibration actuator A1 of [Example 1] in that the guide shaft 30 can be positioned and fixed with high precision by a relatively easy assembly method. However, the shape of the characteristic components that make this possible is different from that of the linear vibration actuator A1 of [Example 1].

The linear vibration actuator A2 has a U-shaped groove 15u formed in a part of the peripheral wall portion 15 of the housing 10 as a positioning shape portion for positioning the guide shaft 30.

The main assembly steps and characteristic components of the linear vibration actuator A2 are explained below with reference to Figure 5.

As shown in Figure 5 (a), the guide shaft 30 is inserted into the retaining portion 21g formed on the frame body 21 of the movable member 20.

As shown in FIG. 5(b), a housing 10 is prepared in which the peripheral wall 15 and bottom wall 12 are integrated. The radius of the bottom of the U-shaped groove 15u formed in part of the peripheral wall 15 is appropriately set based on the press-fit tolerance with respect to the outer diameter of the guide shaft 30. Next, the mover 20 holding the guide shaft 30 is placed inside the peripheral wall 15.

As shown in Fig. 5(c), the ends of the guide shafts 30 are pushed into the U-shaped grooves 15u of the peripheral wall portion 15 and fixed in place. The relative positions of the two guide shafts 30 are determined by the U-shaped grooves 15u.

Next, the assembly process of the linear vibration actuator A2 will be described in more detail with reference to the flow chart shown in Figure 6 (see Figures 4 and 5 for the reference symbols of each part). Note that some of the content that is the same as in [Example 1] will be omitted.

As in [Example 1], the mover 20 holding the guide shaft 30 is prepared through the processes of (1) preparing the mover and (2) assembling the guide shaft into the mover.

[3] Preparation of the Housing Side The second biasing magnet 52 constituting the magnetic spring 50 is adhesively fixed to a predetermined position of the peripheral wall portion 15 constituting the housing 10. Then, the peripheral wall portion 15 and the bottom wall portion 12 constituting the housing 10 are integrated by welding.

[4] Positioning and Fixing of Mover Assembly in Housing The mover 20 holding the guide shaft 30 is positioned inside the housing 10 assembled in [3] and fixed therein.

As in [Example 1], linear vibration actuator A2 is completed by the process of [5] fixing the coil/substrate to the ceiling wall of the housing, and [6] fixing the ceiling wall and peripheral wall of the housing.

As mentioned above, the work processes [1] to [6] may not necessarily be performed in the order listed, but in this embodiment it is essential that the guide shaft 30 is at least held by the movable member 20 and positioned inside the peripheral wall portion 15.

Comparative Example
FIG. 7 is a diagram showing a linear vibration actuator B1 as a comparative example to the embodiment of the present invention.
FIG. 8 is a diagram for explaining main assembly operations and characteristic component parts of the linear vibration actuator B1 shown in FIG.
FIG. 9 is a flow diagram of the assembly work for the linear vibration actuator B1 shown in FIG.

As shown in Figure 7, linear vibration actuator B1 as this comparative example is, like the linear vibration actuators A1 and A2 according to the above-mentioned embodiments, housed in a rectangular box-shaped housing 10. Although not shown in Figure 7, its internal structure also includes a mover 20, a guide shaft 30, a flat coil 40, and a pair of magnetic springs 50, and the basic configuration for rectilinearly vibrating the mover 20 is the same as that of linear vibration actuators A1 and A2.

On the other hand, the comparative linear vibration actuator B1 differs from the embodiment of the present invention in that a round hole 16c that supports the end of the guide shaft 30 is formed in the peripheral wall portion 16 that constitutes the housing 10.

The main assembly steps and characteristic components of the linear vibration actuator B1 are explained below with reference to Figure 8.

As shown in Fig. 8(a), the movable member 20 and the housing 10 in which the peripheral wall 16 and bottom wall 12 are integrated are prepared. At this time, magnets for forming a pair of magnetic springs 50 are arranged and fixed to the movable member 20 and the peripheral wall 16. The peripheral wall 16 also has four circular holes 16c (two marked with the reference numeral 16c in the figure and two on the surface facing these) through which the guide shaft is inserted and supported. The inner diameter of the circular holes 16c is sized to provide a clearance of 10 μm to 15 μm with respect to the outer diameter of the guide shaft.

As shown in Figure 8 (b), with the movable element 20 housed inside the housing 10, the two guide shafts 30 are inserted into the circular holes 16c from outside the housing 10.

As shown in Fig. 8(c), the guide shaft 30 is inserted from the round hole 16c on the outside of the peripheral wall portion 16, and passes through the retaining portion 21g formed on the frame body 21 of the movable member 20 and through the round hole 16c formed on the surface facing the inner surface of the insertion side. At this time, the guide shaft 30 slidably holds the movable member 20, and both ends are supported by the round hole 16c.

Next, the assembly process of the linear vibration actuator B1, which is a comparative example, will be described in more detail with reference to the flow diagram shown in Figure 9. (See Figures 7 and 8 for the reference numerals of each part.) Note that some of the content similar to [Example 1] or [Example 2] will be omitted.

[1] Preparation of the Mover The mover 20 having the first biasing magnet 51 constituting the magnetic spring 50 is prepared by the same process as in [Example 1] and [Example 2].

[2] Preparation of the Housing Side Similar to the process in [Example 2], the second biasing magnet 52 constituting the magnetic spring 50 is adhesively fixed to a predetermined position of the peripheral wall portion 16 constituting the housing 10. Then, the peripheral wall portion 16 and the bottom wall portion 12 constituting the housing 10 are integrated by welding.

[3] Placement of the mover in the housing The mover 20 produced by the process [1] is temporarily placed inside the housing 10 produced by the process [2].

[4] Inserting and fixing the guide shafts Each of the two guide shafts 30 is inserted into the round holes 16c of the peripheral wall 16 from outside the housing 10, and passed through the retaining portions 21g formed on the frame 21 of the mover 20 so that their ends are positioned in the round holes 16c formed in the wall surface of the peripheral wall 16 facing the insertion side. With both ends of the guide shaft 30 supported by the round holes 16c, both ends of the guide shaft 30 are fixed to the peripheral wall 16 by adhesive or welding.

As in [Example 1] and [Example 2], linear vibration actuator B1 is completed by the process of [5] fixing the coil/substrate to the ceiling wall of the housing, and [6] fixing the ceiling wall and peripheral wall of the housing.

As described above, the work processes [1] to [6] do not necessarily have to be performed in the order in which they are performed, but at least it is essential in this comparative example that the guide shaft 30 is inserted from the outside of the housing 10, with the movable member 20 positioned inside the peripheral wall portion 16, and the guide shaft 30 holds the movable member 20 in a slidable manner, and this is a major difference compared to the embodiments of the present invention such as [Example 1] and [Example 2].

Next, taking into consideration the above-mentioned [Example 1] and [Example 2] related to the present invention and the contents of the corresponding <Comparative Example>, the action and effect of the embodiment of the present invention will be explained.

In the conventional assembly method shown in the comparative example, where the mover is placed inside the housing and the guide shaft is inserted from the outside of the peripheral wall of the housing, the linear vibration actuator's characteristics (vibration acceleration, resonance frequency, rise time) tend to vary. One of the reasons for this is that the positioning of the mover is not reproducible, which tends to cause variation in the sliding resistance.

Sliding resistance depends on the clearance of the sliding parts (the mover and the shaft), and the clearance depends on the accumulation of the tolerances of each part. However, with an assembly method in which a guide shaft is inserted from the outside of the housing, if you try to reduce the accumulation of tolerances by tightening the tolerances of the hole position and diameter in the peripheral wall and the outer diameter of the guide shaft, there is a high possibility that the guide shaft will be damaged (scratched or broken) when passing it through the hole. In addition, the magnets in the peripheral wall and the mover are attracted to each other, making the process of passing the shaft difficult.

When assembling the guide shaft by passing it from the outside to the inside of the housing with the movable element positioned inside the housing, for example, the inner diameter of the hole in the peripheral wall through which the guide shaft passes needs to have a clearance of 10 μm to 15 μm for a guide shaft with an outer diameter of φ0.5 mm to φ1.0 mm.

Furthermore, when a magnetic spring is used as the biasing means, the sliding resistance depends on the positioning accuracy of the mating biasing magnet. When the biasing magnet on the moving member approaches the biasing magnet on the peripheral wall, if the biasing magnets are poorly positioned, the flow of magnetic flux will not be uniform on the left and right, and the moving member will receive a force in a direction that is shifted from the vibration direction.

In contrast, with the configuration of the linear vibration actuator according to an embodiment of the present invention, the guide shaft needs to be inserted from the outside of the peripheral wall of the housing, and there is no need to assemble it while holding the mover, making assembly easy.

In addition, the dimensions of the hole or groove formed in the housing to position and hold the guide shaft can be set without any clearance relative to the outer diameter of the guide shaft, allowing the guide shaft to be positioned with high precision. This also allows the positioning precision of the biasing magnet to be set with high precision. This makes it possible to minimize the sliding resistance of the mover and realize a linear vibration actuator with excellent vibration characteristics.

In addition, multiple guide shafts can be arranged with a high degree of parallelism, which suppresses rotation of the mover around the vibration axis and achieves stable linear vibration.

In addition, the applicant has also proposed and described a linear vibration actuator having multiple guide shafts and magnetic springs in the application specification of PCT/JP2019/002943, among others.

The above-described embodiment and several specific examples merely show typical forms of the present invention, and the present invention is not limited to these examples. In other words, the present invention can be implemented with various modifications within the scope of the gist of the invention. As long as such modifications still have the configuration of the linear vibration actuator of the present invention, they are of course included in the scope of the present invention.

For example, in the above embodiment, a magnetic spring using a permanent magnet was used to bias the mover, but a coil spring, leaf spring, or the like may also be used. Also, in the above embodiment, the peripheral wall and bottom wall of the housing are integrated by welding, but they may be machined as one piece from the beginning. Also, in forming each component, the optimal shape can be given within the allowable range according to the processing method used. The present invention is applicable to linear vibration actuators that have two or more guide shafts.

A1, A2 Linear vibration actuator B1 Linear vibration actuator 10 Housing 11, 15, 16 Peripheral wall 12 Bottom wall 13 Ceiling wall 14 Intermediate member 14h Hole 20 Mover 21 Frame 21g Holding portion 30 Guide shaft 40 Flat coil 50 Magnetic spring 51 First biasing magnet 52 Second biasing magnet

Claims (1)

A movable element that vibrates linearly in a predetermined direction;
a plurality of guide shafts that hold the movable element slidably along the direction;
A method for assembling a linear vibration actuator having a housing that surrounds and houses the mover and the guide shaft, comprising the steps of:
a peripheral wall portion of the housing, on both sides in the direction in which the movable element vibrates, is formed with grooves for positioning and fixing both ends of the guide shaft;
With the guide shaft held by a holding portion for the guide shaft formed on the movable member, both ends of the guide shaft are fitted into the grooves, and the movable member and the guide shaft are housed in the housing;
A method for assembling a linear vibration actuator, comprising the steps of: fixing the guide shaft so that it does not move relative to a peripheral wall portion of the housing.

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