Vibration actuator

A first weight portion of a vibration actuator includes an inner-side enlarged portion that protrudes from an end portion of a solid head in a direction of a vibration axis and that is inserted into an opening portion extending within a first compression coil spring along the direction of the vibration axis. An outer peripheral surface of the inner-side enlarged portion becomes continuously smaller in diameter from a base end towards a free end, with the vibration axis being the center of the diameter. That is, the inner-side enlarged portion has the shape of a truncated cone. The inner-side enlarged portion is inserted into the opening portion of the first compression coil spring and the opening portion is utilized to change the length of the inner-side enlarged portion in the direction of the vibration axis, thereby changing the mass of the first weight portion.

CROSS REFERENCES TO RELATED APPLICATIONS

The present invention contains subject matter related to Japanese Patent Application No. 2012-170333 filed in the Japan Patent Office on Jul. 31, 2012, the entire contents of which are incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a small vibration actuator used in, for example, a vibration generating source for notifying a user of an incoming call of a portable wireless device such as a cellular phone, or a vibration generating source for providing tactile sensation of a touch panel of a portable wireless device or reality of a game played by a game device to a user's finger or hand.

2. Description of the Related Art

Hitherto, as a technology in such a field, the technology described in Japanese Unexamined Patent Application Publication No. 2003-220363 (PTL 1) is provided. The vibration actuator described in PTL 1 includes a cup-shaped yoke in a housing (frame). A circular cylindrical magnet is secured to one side of a bottom portion of the yoke and a weight is secured to the other side of the bottom portion of the yoke. A coil is disposed between the magnet and the yoke. In a direction of a vibration axis, a first compression coil spring is disposed between an end portion of the housing and the weight, and a second compression coil spring is disposed between the housing and an open-side end portion of the yoke. By interposing the weight and the yoke between the first compression coil spring and the second compression coil spring in this way, the vibration actuator is reduced in size. In order to prevent rattling of the first compression coil spring, the weight is provided with a protrusion that is fitted into an end portion of the first compression coil spring.

However, in the aforementioned existing vibration actuator, since, in order to prevent rattling of the first compression coil spring, the protrusion of the weight is fitted into the first compression coil spring, an outer peripheral surface of the protrusion of the weight continues contacting an end portion of an inner peripheral surface of the first compression coil spring that is repeatedly stretched and contracted when the weight vibrates. As a result, the first compression coil spring that is repeatedly stretched and contracted when the weight vibrates rubs against or collides with the outer peripheral surface of the protrusion. This may generate abnormal noise from the first compression coil spring at a portion where the first compression coil spring contacts the outer peripheral surface of the protrusion. Further, when the first compression coil spring rubs against or collides with the protrusion, the amplitude of vibration of the weight is affected, thereby causing the vibration quantity to become changeable. In particular, such a problem tends to occur in a small vibration actuator because the wire diameter of the compression coil spring is very small and the compression coil spring, itself, is easily twisted.

With regard to the weight disclosed in PTL 1, there is no technical idea of effectively using the protrusion of the weight as a portion of the weight, and a spring seat is merely formed by forming an end portion of the weight into a concave shape. The evidence for this is that even an end portion of the second compression coil spring that is disposed between the housing and the open-side end portion of the yoke is held by a spring seat having the same shape as the spring seat of the first compression coil spring.

SUMMARY OF THE INVENTION

Accordingly, it is an object of the present invention to provide a vibration actuator that can prevent abnormal noise from being generated and that can achieve stable vibration.

According to an aspect of the present invention, there is provided a vibration actuator in which a magnet vibrates linearly in a housing along a vibration axis as a result of cooperation of a coil and the magnet. The vibration actuator includes the housing, the coil that is disposed in the housing, the magnet that is surrounded by the coil, and a weight that vibrates together with the magnet along the vibration axis. The weight includes a weight body portion and an inner-side enlarged portion. The weight body portion is urged by a compression coil spring disposed along the vibration axis. The inner-side enlarged portion has an outer peripheral surface, protrudes from the weight body portion in a direction of the vibration axis, and is inserted into an opening portion extending within the compression coil spring along the direction of the vibration axis. The outer peripheral surface of the inner-side enlarged portion becomes smaller in diameter from a base end towards a free end, the vibration axis being a center of the diameter.

The weight that is applied to the vibration actuator includes an inner-side enlarged portion that protrudes from the weight body portion in the direction of the vibration axis. The inner-side enlarged portion is inserted into an opening portion of the compression coil spring, and this opening portion is utilized to change the length of the inner-side enlarged portion in the direction of the vibration axis, so that the mass of the weight is changed. Moreover, considering that the length of the inner-side enlarged portion in the opening portion of the compression coil spring is changed, the inner-side enlarged portion is made smaller in diameter from the base end towards the free end, with the vibration axis being the center of the diameter. Therefore, even if the weight is made heavy, the compression coil spring that is repeatedly stretched and contracted when the weight vibrates is less likely to rub against or to collide with the inner-side enlarged portion. As a result, the compression coil spring is less likely to generate abnormal noise. In addition, when the first compression coil spring rubs against or collides with the inner-side enlarged portion, the amplitude of vibration of the weight is affected, thereby causing the vibration quantity to become changeable. However, such a problem is less likely to occur. Further, in the small vibration actuator including a compression coil spring having a very small wire diameter, the compression coil spring, itself, is easily twisted. Therefore, the above-described structure is a very effective structure.

The weight may further include an outer-side enlarged portion that protrudes from the weight body portion at an outer side of the compression coil spring in the direction of the vibration axis.

When such a structure is used, by simply changing the protruding amount of the outer-side enlarged portion, it is possible to easily change the mass of the weight, and to, coupled with a change in the length of the inner-side enlarged portion, considerably increase design flexibility in terms of the mass of the weight.

The outer-side enlarged portion may have an inner peripheral surface that becomes larger in diameter from a base end towards a free end, the vibration axis being a center of the diameter, the inner peripheral surface facing the compression coil spring.

When such a structure is used, the compression coil spring that is repeatedly stretched and contracted when the weight vibrates is less likely to rub against or to collide with the outer-side enlarged portion similarly to the case in which it is less likely to rub against or to collide with the inner-side enlarged portion. Therefore, the compression coil spring is less likely to generate abnormal noise. Further, when the compression coil spring rubs against or collides with the outer-side enlarged portion, the amplitude of vibration of the weight is affected, as a result of which the vibration quantity tends to be changeable. However, such a problem is less likely to occur.

According to another aspect of the present invention, there is provided a vibration actuator in which a magnet vibrates linearly in a housing along a vibration axis as a result of cooperation of a coil and the magnet. The vibration actuator includes the housing, the coil that is disposed in the housing, the magnet that is surrounded by the coil, and a weight that vibrates together with the magnet along the vibration axis. The weight includes a weight body portion and an inner-side enlarged portion. The weight body portion is urged by a compression coil spring disposed along the vibration axis. The inner-side enlarged portion has an outer peripheral surface, protrudes from the weight body portion in a direction of the vibration axis, and is inserted into an opening portion extending within the compression coil spring along the direction of the vibration axis. The outer peripheral surface of the inner-side enlarged portion is smaller in diameter at a free end side than at a base end side, the vibration axis being a center of the diameter.

According to present invention, it is possible to prevent abnormal noise from being generated, and to achieve stable vibration.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Preferred embodiments of a vibration actuator according to the present invention are hereunder described in detail with reference to the drawings.

As shown inFIGS. 1 to 3, a small vibration actuator1includes a parallelepiped housing2that has a height of 4 mm, a width of 6 mm, and a length of 15 mm and that is hollow. A coil3, a parallelepiped magnet4, a first weight portion6, a second weight portion7, a first pole piece8, and a second pole piece9are accommodated in the housing2formed of a magnetic material. The coil3is formed by being wound around a vibration axis L of the housing2into a rectangular shape in cross section. The magnet4is surrounded by the coil3. The first weight portion6and the second weight portion7are disposed adjacent to corresponding sides of the magnet4in a direction of the vibration axis L of the housing2. The first pole piece8and the second pole piece9are affixed to corresponding end surfaces of the magnet4, are annular, and are formed of magnetic materials. The large first weight portion6and the small second weight portion7constitute a weight P.

The first pole piece8is sandwiched by the magnet4and the first weight portion6. The first pole piece8is bonded to the magnet4and the first weight portion6with an adhesive. Similarly, the second pole piece9is sandwiched by the magnet4and the second weight portion7. The second pole piece9is bonded to the magnet4and the second weight portion7with an adhesive. In the vibration actuator1, the magnet4, which constitutes a mover, the first weight portion6, and the second weight portion7vibrate linearly together along a direction of the vibration axis L of the housing2as a result of cooperation of the coil3and the magnet4.

The housing2is divided into two portions, that is, a first housing10and a second housing11in a direction in which the vibration axis L is divided. More specifically, of the portions of the housing2that is divided in two, the first housing10includes a rectangular end wall10aand four side walls10b. The end wall10ais positioned at an end of the housing2in a direction of the vibration axis L. The side walls10bextend in a direction of the vibration axis L from edges of the end wall10a. The first housing10accommodates the first weight portion6, the coil3, and the magnet4.

The second housing11is disposed so as to oppose the first housing10in a direction of the vibration axis L. The second housing11includes a rectangular end wall11aand four side walls11b. The end wall11ais positioned at the other end of the housing2in a direction of the vibration axis L. The side walls11bextend in a direction of the vibration axis L from edges of the end wall11a. The second housing11accommodates the second weight portion7. An open-side end portion of the first housing10and an open-side end portion of the second housing11abut upon each other and are joined to each other by welding. The first housing10and the second housing11are each formed of a magnetic material, such as Steel Plate Cold Commercial (SPCC). A terminal board12d, which is part of a resinous bobbin12, is exposed from a location between the first housing10and the second housing11.

The bobbin12is rectangular in cross section and extends in a direction of the vibration axis L. A first coil portion3A and a second coil portion3B are disposed side by side and wound around the bobbin12. The first coil portion3A and the second coil portion3B that are adjacent to each other are wound in opposite directions, so that currents flow in opposite directions in a peripheral dimension.

A cylindrical portion12aupon which the coil3is wound and that is rectangular in cross section is positioned at substantially the center of the housing2in a direction of the vibration axis L. A flange12bthat is formed at one side of the cylindrical portion12acontacts inner surfaces of the side walls10bof the first housing10. The terminal board12dthat extends along an outer side of the side wall1lb of the second housing11is provided at the other end of the cylindrical portion12a. Terminals12cfor being soldered by reflow to a circuit board that is mounted on a portable wireless device M (seeFIG. 12) are buried in the terminal board12d. By electrically connecting lands of the circuit board and the terminals12c, electric current is supplied to the coil3of the vibration actuator1from the portable wireless device M.

As shown inFIG. 4, the first weight portion6, which constitutes one part of the weight P, includes a weight body portion22that is urged by a first compression coil spring21that is disposed along the vibration axis L. The weight body portion22includes a solid parallelepiped trunk22aand a solid parallelepiped head22b. The trunk22ais inserted into the cylindrical portion12a(seeFIG. 3) of the bobbin12and slides along the cylindrical portion12ain a direction of the vibration axis L. The head22bis integrated to an end portion of the trunk22aand is enlarged outward from the trunk22a. The trunk22aincludes a protrusion22cthat is inserted into a center opening of the annular first pole piece8.

The first weight portion6includes an inner-side enlarged portion23that protrudes from an end portion of the solid head22bin a direction of the vibration axis L and that is inserted into an opening portion S1extending within the first compression coil spring21along the direction of the vibration axis L. An outer peripheral surface23aof the inner-side enlarged portion23becomes continuously smaller in diameter from a base end towards a free end, with the vibration axis L being the center of the diameter. That is, the inner-side enlarged portion23has the shape of a truncated cone.

The inner-side enlarged portion23is inserted into the opening portion S1of the first compression coil spring21and the opening portion S1is utilized to change the length of the inner-side enlarged portion23in the direction of the vibration axis L, thereby changing the mass of the first weight portion6. Moreover, considering that the length of the inner-side enlarged portion23in the opening portion S1of the compression coil spring21is changed, the inner-side enlarged portion23is made smaller in diameter from the base end towards the free end, with the vibration axis L being the center of the diameter. Therefore, even if the first weight portion6is made heavy, the first compression coil spring21that is repeatedly stretched and contracted when the first weight portion6vibrates is less likely to rub against or to collide with the inner-side enlarged portion23. As a result, the compression coil spring21is less likely to generate abnormal noise.

Further, when the first compression coil spring21rubs against or collides with the inner-side enlarged portion23, the amplitude of vibration of the first weight portion6is affected, thereby causing the vibration quantity to become changeable. However, such a problem is less likely to occur. In the small vibration actuator1including the first compression coil spring21having a very small wire diameter, the first compression coil spring21, itself, is easily twisted. Therefore, the above-described structure is a very effective structure.

Further, the first weight portion6includes an outer-side enlarged portion24that protrudes from the head22bof the weight body portion22at the outer side of the first compression coil spring21in the direction of the vibration axis L. The outer-side enlarged portion24extends around the entire periphery of the first compression coil spring21. An outer peripheral surface24bof the outer-side enlarged portion24is flush with an outer peripheral surface22dof the head22b. When such a structure is used, by simply changing the protruding amount of the outer-side enlarged portion24, it is possible to easily change the mass of the first weight portion6, and to, coupled with a change in the length of the inner-side enlarged portion23, considerably increase design flexibility in terms of the mass of the first weight portion6.

An inner peripheral surface24a(facing the first compression coil spring21) of the outer-side enlarged portion24becomes continuously larger in diameter from a base end towards a free end, with the vibration axis L being the center of the diameter. When such a structure is used, the compression coil spring21that is repeatedly stretched and contracted when the first weight portion6vibrates is less likely to rub against or to collide with the outer-side enlarged portion24similarly to the case in which it is less likely to rub against or to collide with the inner-side enlarged portion23. Therefore, the compression coil spring21is less likely to generate abnormal noise. Further, when the compression coil spring21rubs against or collides with the outer-side enlarged portion24, the amplitude of vibration of the first weight portion6is affected, as a result of which the vibration quantity tends to be changeable. However, such a problem is less likely to occur.

As shown inFIGS. 4 and 5, one end of the first compression coil spring21contacts a bottom surface26aof a spring accommodating recess26that is formed between the inner-side enlarged portion23and the outer-side enlarged portion24, and the other end of the first compression coil spring21is inserted into a protruding seat10cthat is formed at the center of the rectangular end wall10aof the housing10, so that seating stability of the first compression coil spring21around the seat10cis provided.

As shown inFIG. 6, the second weight portion7, which is the other part of the weight P, is smaller and lighter than the first weight portion6. The second weight portion7includes a weight body portion32that is urged by a second compression coil spring31that is disposed along the vibration axis L. The weight body portion32is a solid parallelepiped weight body portion that is inserted into the cylindrical portion12a(seeFIG. 3) of the bobbin12and slides along the cylindrical portion12ain a direction of the vibration axis L. The weight body portion32corresponds to the trunk22aof the first weight portion6. Although a head is not provided at the weight body portion32due to the existence of the terminal board12d, a head may be provided. The weight body portion32includes a protrusion32athat is inserted into a center opening of the annular second pole piece9.

The second weight portion7includes an inner-side enlarged portion33that protrudes from an end portion of the solid weight body portion32in a direction of the vibration axis L and that is inserted into an opening portion S2extending in the second compression coil spring31along the direction of the vibration axis L. An outer peripheral surface33aof the inner-side enlarged portion33becomes continuously smaller in diameter from a base end towards a free end, with the vibration axis L being the center of the diameter. That is, the inner-side enlarged portion33has the shape of a truncated cone. The inner-side enlarged portion33provides operation effects that are the same as those of the above-described inner-side enlarged portion23.

Further, the second weight portion7includes an outer-side enlarged portion34that protrudes from an end portion of the weight body portion32at the outer side of the second compression coil spring31in the direction of the vibration axis L. Although the outer-side enlarged portion34surrounds the second compression coil spring31, a portion of the outer-side enlarged portion34is cut away. The outer-side enlarged portion34includes opposing long-side side surfaces34aand opposing short-side side surfaces34b. In order to make it possible to increase the diameter of the second compression coil spring31, a C-shaped cutaway portion C that extend to opposite positions in a radial direction are formed in the long-side side surfaces34a. The larger the spring diameter, the more stably the spring is capable of being stretched and contracted. The cutaway portion C reaches a spring accommodating recess36that is formed between the inner-side enlarged portion33and the outer-side enlarged portion34and allows the second compression coil spring31to be exposed. Reference character F denotes a chamfered portion around the cutaway portion C. An inner peripheral surface34cof the outer-side enlarged portion34increases continuously in diameter from a base end towards a free end, the vibration axis L being the center of the diameter. The outer-side enlarged portion34provides operation effects that are the same as those of the above-described outer-side enlarged portion24.

As shown inFIG. 2, one end of the second compression coil spring31contacts a bottom surface36aof the spring accommodating recess36that is formed between the inner-side enlarged portion33and the outer-side enlarged portion34, and the other end of the second compression coil spring31is inserted into a protruding seat11cthat is formed at the center of the rectangular end wall11aof the housing11, so that seating stability of the second compression coil spring31around the seat11cis provided.

A cylindrical slider38that has a small wall thickness and that is rectangular in cross section surrounds the magnet4, the trunk22aof the weight body portion22of the first weight portion6, and the weight body portion32of the second weight portion7, and is secured to the outer surface of the magnet4, the outer surface of the first weight portion6, and the outer surface of the second weight portion7with an adhesive. Using the cylindrical slider38makes it possible to smoothly vibrate the magnet4, the first weight portion6, and the second weight portion7along an inner surface of the cylindrical portion12aof the bobbin12in a direction of the vibration axis L.

The present invention is not limited to the above-described embodiment, so that various modifications can be made without departing from the gist of the present invention. In describing an embodiment below, structural features that are the same as or equivalent to those of the above-described vibration actuator1are given the same reference numerals and are not described below.

As shown inFIG. 7, in a first weight portion40, which is a modification, an outer peripheral surface41aof an inner-side enlarged portion41thereof becomes smaller stepwise in diameter from a base end towards a free end, with the vibration axis L being the center of the diameter. An inner peripheral surface42aof an outer-side enlarged portion42extends in a direction of the vibration axis L. Here, in a radial direction that is orthogonal to the vibration axis L, a gap exists between the inner peripheral surface42aand the first compression coil spring21. The inner peripheral surface42aof the outer-side enlarged portion42may be made larger stepwise from the base end towards the free end.

Similarly to the second weight portion7, the first weight portions6and40may each include a cutaway portion C (seeFIG. 6). Alternatively, the second weight portion7need not include the cutaway portion C.

As shown inFIG. 8, in a different first weight portion44, an inner-side enlarged portion46having the shape of a truncated cone is provided at a head45aof a weight body portion45, and an outer-side enlarged portion is not provided.

As shown inFIG. 9, a vibration actuator1A includes a guide shaft50that extends through a magnet4, a first weight portion6, and a second weight portion7in a direction of a vibration axis L. End walls10aand11aof a housing2are secured to corresponding ends of the guide shaft50by welding.

As shown inFIGS. 10 and 11, a bobbin12, which is a modification, includes protrusions12ethat protrude inward from an inner surface of a cylindrical portion12a. The protrusions12eextend along a direction of the vibration axis L. When the cylindrical slider38to which the magnet4, the first weight portion6, and the second weight portion7are secured slides along the protrusions12e, the magnet4, the first weight portion6, and the second weight portion7can be even more smoothly vibrated in a direction of the vibration axis L. The number of protrusions12emay be selected as appropriate.

The outer peripheral surface23aof the inner-side enlarged portion23is made continuously smaller from the base end towards the free end so that a gap is formed between it and the first compression coil spring21in a radial direction that is orthogonal to the vibration axis L, the outer peripheral surface33aof the inner-side enlarged portion33is made continuously smaller from the base end towards the free end so that a gap is formed between it and the second compression coil spring31in a radial direction that is orthogonal to the vibration axis L, and the outer peripheral surface41aof the inner-side enlarged portion41is made smaller stepwise from the base end towards the free end so that a gap is formed between it and the first compression coil spring21in a radial direction that is orthogonal to the vibration axis L. However, the following structures are possible. Each of the outer peripheral surfaces23aand41amay extend in a direction of the vibration axis L so that a gap is formed between it and the first compression coil spring21in a radial direction that is orthogonal to the vibration axis L. The outer peripheral surface33amay extend in a direction of the vibration axis L so that a gap is formed between it and the second compression coil spring31in a radial direction that is orthogonal to the vibration axis L.