Vibration motor

A vibration motor includes a stationary part, and a movable element which has a magnet and can vibrate in one direction. The stationary part includes a coil which applies a driving force to the magnet due to energization, a housing which houses the movable element and the coil therein, a first lid part which closes an end portion of the housing on one side in the one direction, and a first bearing part. The first bearing part is disposed inside the housing on the other side in the one direction from the first lid part. The first bearing part includes a bearing inner circumferential surface disposed with a gap therebetween with respect to an outer circumferential surface of a portion of the movable element on one side in the one direction.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 to Japanese Application No. 2020-119456 filed on Jul. 10, 2020, and No. 2021-013174 filed on Jan. 29, 2021, the entire contents of which are hereby incorporated herein by reference.

FIELD OF THE INVENTION

The disclosure relates to a vibration motor.

BACKGROUND

Conventionally, a vibration motor as a vibration generation device is often included in devices of various types such as mobile devices such as smartphones. Vibration motors are often used, for example, in applications such as a function of notifying a user of an incoming call, an alarm, or the like, or a function of tactile feedback in a human interface.

A conventional vibration motor may include, for example, a housing, a coil, an elastic member, and a movable element. The movable element includes a magnet. The movable element and the housing are connected by an elastic member. The movable element vibrates when the coil is energized and a magnetic field is generated.

However, when the above-described housing is formed of a magnetic material, there has been a likelihood that a phenomenon in which the movable element is attracted and sticks to an inner surface of the housing by an attractive force and the movable element is not moved will occur. Further, the reason why the housing is formed of a magnetic material is to form a magnetic circuit to increase a magnetic force.

SUMMARY

According to an exemplary embodiment of the disclosure, there is provided a vibration motor including a stationary part, and a movable element which has a magnet and can vibrate in one direction. The stationary part includes a coil which applies a driving force to the magnet due to energization, a housing which houses the movable element and the coil therein, a first lid part which closes an end portion of the housing on one side in the one direction, and a first bearing part. The first bearing part is disposed inside the housing on the other side in the one direction from the first lid part. The first bearing part includes a bearing inner circumferential surface disposed with a gap therebetween with respect to an outer circumferential surface of a portion of the movable element on one side in the one direction.

The above and other elements, features, steps, characteristics and advantages of the disclosure will become more apparent from the following detailed description of the preferred embodiments with reference to the attached drawings.

DETAILED DESCRIPTION

Hereinafter, exemplary embodiments of the disclosure will be described with reference to the drawings.

In the drawings, one direction in which a movable element vibrates is illustrated as an X direction, one side in the one direction is illustrated as X1, and the other side in the one direction is illustrated as X2.

First, a first exemplary embodiment of the disclosure will be described.FIG.1is a cross-sectional perspective view of a vibration motor10according to a first exemplary embodiment of the disclosure.FIG.2is a side cross-sectional view of the vibration motor10illustrated inFIG.1.

The vibration motor10includes a stationary part1, a movable element2, and an elastic member3. The movable element2can vibrate in one direction (X direction).

The stationary part1includes a housing11, a first sleeve bearing12, and a coil14. The housing11is a cylindrical member extending in one direction. Further, the housing11is not limited to a cylindrical shape, and may be, for example, a quadrangular cylindrical shape or the like. The housing11is formed of a magnetic material. The above-described magnetic material may be, for example, stainless steel.

The first sleeve bearing12includes a first lid part121and a first bearing part122. That is, the stationary part1includes the first lid part121and the first bearing part122. The first lid part121has a substantially disc shape. The first bearing part122has a substantially cylindrical shape that protrudes from the first lid part121toward the other side in one direction and extends in one direction. Further, the first lid part121is not limited to a substantially disc shape, and may be, for example, a substantially quadrangular plate shape, and the first bearing part122is not limited to a substantially cylindrical shape, and may be, for example, a substantially quadrangular cylindrical shape. The first lid part121and the first bearing part122form the first sleeve bearing12serving as a single member. Further, the first lid part121and the first bearing part122may be separate bodies. In that case, the first lid part121and the housing11may form a single member.

The first sleeve bearing12is inserted into the housing11from one side of the housing11in one direction and fixed to the housing11. The first lid part121closes an end portion on one side of the housing11in one direction. The first bearing part122is disposed inside the housing11on the other side of the first lid part121in one direction.

The first sleeve bearing12may be formed of, for example, a resin having a low friction coefficient and a low wear property. As the resin described above, for example, POM (polyacetal) may be used.

The stationary part1includes a second lid part13. The second lid part13has a substantially disc shape and closes an end portion on the other side of the housing11in one direction. Further, the second lid part13is not limited to a substantially disc shape, and may be, for example, a substantially quadrangular plate shape. The housing11, the first lid part121, and the second lid part13form a body.

The coil14is formed by winding a lead wire around a central axis J extending in one direction of the movable element2and is fixed to an inner surface of the housing11. That is, the housing11houses the coil14inside. The coil14generates a magnetic field when it is energized. The coil14is fixed to an end surface of the first bearing part122on the other side in one direction.

The movable element2includes a magnet21, and a magnetic material22, and a holder23and is housed inside the housing11. The magnet21includes a magnet part21A on one side in one direction and a magnet part21B on the other side in one direction. The magnetic material22is sandwiched by the magnet parts21A and21B from both sides in one direction. The magnet parts21A and21B and the magnetic material22form a substantially columnar shape extending in one direction. Further, the magnet parts21A and21B and the magnetic material22are not limited to forming a substantially columnar shape, and may form, for example, a substantially quadrangular columnar shape.

The other side of the magnet part21A in one direction is an N pole, and one side thereof in one direction is an S pole. One side of the magnet part21B in one direction is an N pole, and the other side thereof in one direction is an S pole. That is, the N poles face each other in one direction with the magnetic material22sandwiched therebetween. When the housing11is formed of a magnetic material, a magnetic field generated by the magnet21and the coil14is inhibited from leaking to the outside of the vibration motor10, and a magnetic force can be increased. Further, the S poles may face each other in one direction with the magnetic material22sandwiched therebetween.

The holder23holds a portion of the magnet part21B (the magnet21) on the other side in one direction. The holder23includes a columnar recessed part23A that is recessed to the other side in one direction in a columnar shape. A portion of the magnet part21B on the other side in one direction is fitted into the columnar recessed part23A. The holder23functions as a weight (sinker) and may be formed of, for example, a tungsten alloy.

The elastic member3is a coil spring that is wound around the central axis J. An end portion of the elastic member3on one side in one direction is fixed to an end surface of the holder23on the other side in one direction, and an end portion of the elastic member3on the other side in one direction is fixed to an inner surface of the second lid part13. Fixing of the elastic member3may be performed, for example, by adhesion. That is, the elastic member3is disposed between the holder23and the second lid part13. Further, fixing of the elastic member3is not limited to adhesion, and may also be performed by, for example, welding, fitting, caulking, or the like.

The first bearing part122has a cylindrical bearing inner circumferential surface122A. In a case of non-operating state in which the coil14is not energized and the movable element2is in a stationary state, a portion of the magnet part21A on one side in one direction is housed inside the first bearing part122with a gap S1between itself and the bearing inner circumferential surface122A. That is, the first bearing part122has the bearing inner circumferential surface122A disposed with the gap S1with respect to an outer circumferential surface of a portion P1of the movable element2on one side in one direction. Further,FIGS.1and2illustrate the vibration motor10in a non-operating state.

In a non-operating state, the magnetic material22is positioned on an inner side of the coil14. In a non-operating state, although the elastic member3has a natural length, fixing of the elastic member3to the movable element2by the holder23is facilitated.

When the coil14is energized, a driving force is applied to the magnet21by an interaction between a magnetic field generated by the coil14and a magnetic field generated by the magnet21. That is, when the driving force is applied to the movable element2, the movable element2vibrates in one direction.

At the time of vibration of the movable element2, when the movable element2comes into contact with the bearing inner circumferential surface122A of the first bearing part122, since the movable element2slides with respect to the stationary first bearing part122, movement of the movable element2is limited to movement in one direction. Thereby, occurrence of a phenomenon in which the movable element2is attracted and sticks to the housing11formed of a magnetic material by an attractive force can be suppressed, and the movable element2can be stably operated.

Also, when the movable element2moves to one side in one direction, the movable element2compresses air contained in a space surrounded by the first bearing part122and the first lid part121, and thereby an effect of a damper is exhibited. Thereby, the movable element2is inhibited from coming into contact with the first lid part121.

Also, when a configuration of a vibration motor in which two elastic members are provided by disposing the elastic members on one side and the other side in one direction is assumed, there is a likelihood that characteristics of the elastic members will be inconsistent, and thereby product performance such as a resonance frequency is difficult to be stabilized. On the other hand, in the configuration of the present embodiment, since there is only one elastic member3, stabilization in product performance can be achieved. Also, compared to the configuration in which a holder and an elastic member are provided on one side in one direction when two elastic members are provided as described above, in the configuration of the present embodiment, costs can be reduced because the above-described holder and the above-described elastic member can be replaced with the first bearing part122.

Hereinafter, various modified examples of the above-described first embodiment will be described. Further, the various modified examples to be described below can be implemented in appropriate combinations.

FIG.3is a side cross-sectional view of a vibration motor101according to a first modified example. As illustrated inFIG.3, in the first modified example, a groove part1221is provided in the first bearing part122. The groove part1221is provided on the bearing inner circumferential surface122A. The groove part1221extends in one direction. Further, the groove part1221is included in the gap S1.

FIG.4is a front view of a part of the first bearing part122from the other side in one direction. As illustrated inFIG.4, a plurality of groove parts1221is provided. Further, the number of groove parts1221may be one. That is, the bearing inner circumferential surface122A includes at least one groove part1221provided in one direction.

An end surface1221A of the groove part1221on the other side in one direction opens at an end surface122B of the first bearing part122on the other side in one direction. That is, the end surface1221A of the groove part1221on the other side in one direction is positioned at the end surface122B of the first bearing part122on the other side in one direction.

Also, an end surface1221B of the groove part1221on one side in one direction is positioned on the other side in one direction with respect to an end surface122C of the first bearing part122on one side in one direction.

In such a first modified example, as illustrated inFIG.5, when the movable element2(the magnet part21A) moves to one side in one direction in an operating state, air compressed by the movable element2escapes to the groove part1221. Further, an air flow F1is denoted inFIG.5. Thereby, the effect of a damper is weakened, and sliding ability of the movable element2can be improved.

Also, since the air that has escaped to the groove part1221flows out to the outside from the end surface1221A on the other side in one direction, the air can easily escape and the sliding ability of the movable element2can be further improved.

Also, as illustrated inFIG.6, when the movable element2moves in one direction, if the movable element2moving toward one side in one direction passes the end surface1221B on one side in one direction, the escape of the air is suppressed and resistance due to the air increases. Therefore, the movable element2can be inhibited from coming into contact with the first lid part121.

FIG.7is a side cross-sectional view of a vibration motor102according to a second modified example. The vibration motor102includes buffer members41and42. The buffer members41and42may be formed of, for example, silicon rubber, thermoplastic polyurethane, or the like.

The buffer member41is fixed to an inner surface of the first lid part121facing an end surface T1on one side in one direction of the movable element2(the magnet part21A) in one direction. The buffer member42is fixed to an inner surface of the second lid part13facing an end surface T2on the other side in one direction of the movable element2(the holder23) in one direction. Fixing of the buffer members41and42may be performed by, for example, a double-sided tape.

Further, only one of the buffer members41and42may be provided. That is, the stationary part1includes the buffer members41and42disposed on at least one of the inner surface of the first lid part121facing the end surface T1on one side in one direction of the movable element2in one direction and the inner surface of the second lid part13facing the end surface T2on the other side in one direction of the movable element2in one direction.

The movable element2does not come into contact with the buffer members41and42during a normal operation. However, when the vibration motor102is dropped, the end surface T1of the movable element2on one side in one direction may come into contact with the buffer member41or the end surface T2of the movable element2on the other side in one direction may come into contact with the buffer member42. Therefore, an unwanted sound or the like due to a contact between the movable element2and the stationary part1can be suppressed.

As a third modified example, in the vibration motor10according to the above-described first embodiment, a lubricant or a magnetic fluid may be disposed in the gap S1. The lubricant may be, for example, an oil. When a magnetic fluid is disposed, the magnetic fluid moves together with the magnet part21A.

Thereby, the movable element2easily moves in one direction. Also, wear of the movable element2can be suppressed and a prolonged life can be achieved. Further, generation of sound due to friction between the movable element2and the first bearing part122can be suppressed, and quietness can be improved.

FIG.8is a side cross-sectional view of a vibration motor104according to a fourth modified example. As illustrated inFIG.8, in the vibration motor104, the first bearing part122includes an air passage1222and an air hole1223. The air passage1222is disposed in one direction. The air hole1223communicates with the air passage1222and is disposed on the bearing inner circumferential surface122A.

InFIG.8, the other side of the air passage1222in one direction does not extend to the end surface of the first bearing part122on the other side in one direction. As in an embodiment to be described later, the air passage may extend to the end surface of the first bearing part122on the other side in one direction and open. Also, the air passage may extend to one side of the air hole1223in one direction. In that case, the air passage may extend to an end surface of the first lid part121on one side in one direction and open.

According to the configuration illustrated inFIG.8, as illustrated inFIG.9, when the movable element2moves in one direction, in a case in which the movable element2is positioned on the other side of the air hole1223in one direction, air compressed by the movable element2flows into the air passage1222through the air hole1223, and the movable element2easily moves to one side in one direction. Further, an air flow F2is denoted inFIG.9. Then, as illustrated inFIG.10, when the movable element2passes the air hole1223toward one side in one direction, the air hole1223is closed to suppress escape of the air, and resistance due to the air increases. Accordingly, the movable element2can be inhibited from coming into contact with the first lid part121.

Further, the set of the air passage and the air hole is not limited to one set, and a plurality of sets may be provided to be aligned in the circumferential direction of the first bearing part122.

FIG.11is a side cross-sectional view of a vibration motor105according to a fifth modified example. As illustrated inFIG.11, in the vibration motor105, a first outer circumferential member24that covers an outer circumferential surface of the magnet part21A is formed. That is, the portion P1of the movable element2on one side in one direction includes a portion211of the magnet21(the magnet part21A) and the first outer circumferential member24disposed on the outer circumferential surface of the portion211. The first outer circumferential member24may be formed of, for example, a fluorine layer or the like having a low friction coefficient.

According to such a configuration, wear of the magnet21due to the sliding operation of the movable element2in contact with the bearing inner circumferential surface122A can be suppressed, and change in magnetic flux due to the wear can be suppressed. Also, a rattling generated due to wear of the movable element2when a portion of the movable element2on the other side in one direction moves to a direction other than one direction can be suppressed. Accordingly, coaxiality of the movable element2can be improved. Further, coaxiality indicates a deviation of an axial line from a specified axial line to be matched. Here, the specified axis line is the central axis J.

FIG.12is a side cross-sectional view of a vibration motor106according to a sixth modified example. As illustrated inFIG.12, in the vibration motor106, the movable element2includes a second outer circumferential member25. The second outer circumferential member25is disposed on an outer circumferential surface of the holder23and slides with respect to the inner surface of the housing11. As in the first outer circumferential member24, the second outer circumferential member25may be formed of, for example, a fluorine layer or the like.

According to such a configuration, a rattling caused by the portion of the movable element2on the other side in one direction moving to a direction other than one direction can be suppressed and coaxiality of the movable element2can be improved. Also, when a configuration in which the outer circumferential member25is not provided is assumed, in order to inhibit the movable element2from being attracted and sticking to the housing11formed of a magnetic material by an attractive force, it is necessary to provide a gap between the outer circumferential surface of the holder23and the inner surface of the housing11to some extent. Then, when the vibration motor is reduced in size, a size of the holder23as a weight is reduced. On the other hand, in the present embodiment, since the outer circumferential member25is provided, even when the outer circumferential surface of the holder23is brought close to the inner surface of the housing11, the movable element2can be inhibited from being attracted and sticking, and thereby the movable element2can be stably operated. Also, also when the vibration motor106is reduced in size, the size of the holder23as a weight can be increased. Accordingly, vibration performance of the vibration motor106can be improved.

FIG.13is a side cross-sectional view of a vibration motor107according to a seventh modified example. As illustrated inFIG.13, in the vibration motor107, the first lid part121has a through hole121A penetrating in one direction. A plurality of through holes121A is provided. Further, the number of through holes121A may be one. That is, the first lid part121has at least one through hole121A penetrating in one direction. Also, the through hole121A is disposed at an inner surface of the first lid part121facing the end surface T1on one side in one direction of the movable element2in one direction.

According to such a configuration, when the movable element2moves in one direction, since air escapes from the through hole121A to the outside, the movable element2can easily move.

Next, a second exemplary embodiment of the disclosure will be described.FIG.14is a cross-sectional perspective view of a vibration motor20according to a second exemplary embodiment of the disclosure. A difference in a configuration of the vibration motor20from that of the first embodiment is that it includes a second sleeve bearing15.

A stationary part1includes the second sleeve bearing15. The second sleeve bearing15includes a second lid part151and a second bearing part152. That is, the stationary part1includes the second lid part151and the second bearing part152.

The second lid part151has a substantially disc shape. The second bearing part152has a substantially cylindrical shape that protrudes from the second lid part151toward one side in one direction and extends in one direction. The second lid part151and the second bearing part152form the second sleeve bearing15as a single member. Further, various modified examples of the configuration of the second sleeve bearing15are the same as those of the first sleeve bearing12described above.

The second sleeve bearing15is inserted into a housing11from the other side of the housing11in one direction and fixed to the housing11. The second lid part151closes an end portion on the other side of the housing11in one direction. The second bearing part152is disposed inside the housing11on the other side of a first bearing part122in one direction and on one side of the second lid part151in one direction.

The second sleeve bearing15may be formed of, for example, a resin having a low friction coefficient and a low wear property. As the resin described above, for example, POM (polyacetal) may be used.

The second bearing part152has a cylindrical bearing inner circumferential surface152A. In a case of non-operating state, a portion of a magnet part21B on the other side in one direction is housed inside the second bearing part152with a gap S2between itself and the bearing inner circumferential surface152A. That is, the second bearing part152has the bearing inner circumferential surface152A disposed with the gap S2with respect to an outer circumferential surface of a portion P2of a movable element2on the other side in one direction. Further,FIG.14illustrates the vibration motor20in a non-operating state.

When a coil14is energized, a driving force is applied to a magnet21, and the movable element2vibrates in one direction. At the time of vibration of the movable element2, when the movable element2comes into contact with the bearing inner circumferential surfaces122A and152A, since the movable element2slides with respect to the stationary first bearing part122and second bearing part152, movement of the movable element2is limited to movement in substantially one direction. Thereby, the movable element2can be inhibited from sticking, and the movable element2can be stably operated.

Also, when the movable element2moves to the other side in one direction, the movable element2compresses air contained in a space surrounded by the second bearing part152and the second lid part151, an effect of a damper is exhibited, and the movable element2can be inhibited from coming into contact with the second lid part151.

Further, in the present embodiment, since the holder and the elastic member are replaced with the bearing part, costs can be further reduced compared to the first embodiment.

Further, in the configuration illustrated inFIG.14, the first bearing part122has an air passage1222and an air hole1223, and the second bearing part152has an air passage1522and an air hole1523.

The air passage1222extends toward the other side in one direction from the air hole1223to an end surface of the first bearing part122on the other side in one direction and opens. That is, an end surface1222A of the air passage1222on the other side in one direction is positioned at the end surface of the first bearing part122on the other side in one direction.

Thereby, when the movable element2moves to one side in one direction, air compressed by the movable element2flows into the air passage1222through the air hole1223and flows out from the end surface1222A on the other side in one direction to the outside. Accordingly, the air easily escapes, and the movable element2easily moves to one side in one direction.

The air passage1522extends toward one side in one direction from the air hole1523to an end surface of the second bearing part152on one side in one direction and opens. That is, an end surface1522A of the air passage1522on one side in one direction is positioned at the end surface of the second bearing part152on one side in one direction.

Thereby, when the movable element2moves to the other side in one direction, air compressed by the movable element2flows into the air passage1522through the air hole1523and flows out from the end surface1522A on one side in one direction to the outside. Accordingly, the air easily escapes, and the movable element2easily moves to the other side in one direction. Further, when the movable element2passes the air hole1523toward the other side in one direction, since the air hole1523is closed, the effect of a damper is strengthened, and the movable element2can be inhibited from coming into contact with the second lid part151.

Further, various modified examples of the first embodiment described above can be appropriately applied to the present embodiment.

The exemplary embodiments of the disclosure have been described above. Further, the scope of the disclosure is not limited to the above-described embodiments. The disclosure can be implemented with various modifications made to the above-described embodiments without departing from the gist of the disclosure.

The disclosure can be used, for example, in vibration motors mounted on devices of various types such as mobile devices.

Features of the above-described preferred embodiments and the modified examples thereof may be combined appropriately as long as no conflict arises.