Vibration actuator

A vibration actuator has a frame; a first spring, supported on one end within the frame and the other end vibrates along an axial direction. A second spring, supported on one end within the frame, and the other end vibrates along the axial direction. A first weight connected to the other end of the first spring and a second weight connected to the other end of the second spring. A magnet portion protrudes in the axial direction is in the first weight and a coil wrapped around the magnet portion is in the second weight. A driving current of a frequency that is a first resonant frequency set by the spring constant of the first spring and the mass of the first weight or a second resonant frequency set by the spring constant of the second spring and the mass of the second weight is applied to the coil.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a U.S. national phase application under 35 U.S.C. § 371 of International Patent Application No. PCT/JP2017/015376, filed Apr. 14, 2017, and claims benefit of priority to Japanese Patent Application No. 2016-106477, filed May 27, 2016. The entire contents of these applications are hereby incorporated by reference.

FIELD OF TECHNOLOGY

The present invention relates to a vibration actuator.

BACKGROUND

Vibration actuators (or “vibration motors”) are built into mobile electronic devices, and are broadly used as devices to communicate to the user, through a vibration, that there is an incoming call, or that a signal, such as an alarm, has been generated, and have become indispensable devices in wearable devices, which are carried on the body of the user. Moreover, in recent years vibration actuators have been of interest as devices by which to achieve haptics (skin-sensed feedback) in the human interfaces such as touch panels.

Among the various forms of vibration actuators that are under development, vibration actuators that are able to generate relatively large vibrations through linear reciprocating vibrations of a movable element are of particular interest. Such vibration actuators are provided with a weight and a magnet on a movable element side, where an electric current is applied to a coil that is provided on the stator side to cause the Lorentz forces that act on the magnet to form a driving force, to cause the movable element, which is elastically supported along the direction of vibration, to undergo reciprocating vibrations in the axial direction (referencing Japanese Unexamined Patent Application Publication 2016-73941).

SUMMARY

This type of vibration actuator can produce a vibration with a large amplitude through applying, to the coil, an alternating current or a pulsed current with the resonant frequency that is set by the spring constants of the spring that elastically supports the movable element and the mass of the movable element (weight). However, because the resonant frequency has a single value for the vibration actuator, one vibration actuator can produce only one type of effective vibration, and thus there is a problem in that it is not possible to provide a different type of vibration sensation with a single vibration actuator.

The present invention is proposed in order to handle this type of situation, and the problems solved by the present invention is to enable the provision of different types of vibration sensations using a single vibration actuator, to enable a high degree of freedom in setting the frequencies of the vibrations that are set at that time, and so forth.

In order to solve such a problem, the vibration actuator according to the present invention is provided with the following structures:

A vibration actuator comprising: a frame; a first spring, supported on one end side within the frame, wherein the other end side is able to vibrate along an axial direction; a second spring, supported on one end side within the frame, wherein the other end side is able to vibrate along the axial direction; a first weight that is connected to the other end side of the first spring; and a second weight that is connected to the other end side of the second spring, wherein: a magnet portion that protrudes in the axial direction is provided in the first weight; a coil that is wrapped around the magnet portion is provided in the second weight; and a driving current of a frequency that is either a first resonant frequency that is set by the spring constant of the first spring and the mass of the first weight or a second resonant frequency that is set by the spring constant of the second spring and the mass of the second weight is applied to the coil.

DETAILED DESCRIPTION

Embodiments according to the present invention will be explained below in reference to the drawings. In the descriptions below, identical reference symbols in the different drawings below indicate positions with identical functions, and redundant explanations in the various drawings are omitted as appropriate.

InFIG. 1andFIG. 2, the vibration actuator1comprises: a frame2; a first spring3, having one end side thereof supported within the frame2and the other end side able to vibrate along the axial direction (the direction along the axis O in the figures); a second spring4, having one end side thereof supported within the frame2and the other end side able to vibrate along the axial direction (the direction along the axis O in the figures); a first weight5that is connected to the other end side of the first spring3; and a second weight6that is connected to the other end side of the second spring4. The frame2is a stationary element, and contains the first spring3and first weight5, and the second spring4and second weight6, which are movable elements.

There is no particular limitation on the shape of the frame2, but, in the example in the figure, it is a round cylindrical shape that has a top face2A, a bottom face2B, and a side surface2C. Moreover, as illustrated inFIG. 2, in the frame2, the side surface2C is separated in the axial direction (the direction along the axis O in the figure), and has a first frame2X, which has a top face2A, and a second frame2Y, which has a bottom face2B. The axis O in the figure is the axis of the round cylindrical frame2, and the first frame2X and the second frame2Y are connected coaxially. In the example in the figure, a fitting protruding portion2C1is provided in the side surface2C of the first frame2X, and a fitting recessed portion2C2is provided in the side surface2C of the second frame2Y, and when connecting the first frame2X and the second frame2Y, the fitting protruding portion2C1is fitted into the fitting recessed portion2C2.

In the example in the figure, the first spring3a disk-shaped leaf spring wherein the outer peripheral edge portion3A is secured to the top face2A of the frame2, with one end side supported on the first frame2X side, and the inner peripheral edge portion3B is secured to the top end face of the first weight5. Moreover, the second spring4is a disk-shaped leaf spring wherein the outer peripheral edge portion4A is secured to the side surface2C of the frame2, one end side is supported on the second frame2Y side, and the inner peripheral edge portion4B is secured to the second weight6.

A protruding portion4A1is provided on the outer peripheral edge portion4A of the second spring4, where the protruding portion4A1fits into the fitting recessed portion2C2that is provided in the side surface2C of the second frame2Y. Given this, when connecting the first frame2X and the second frame2Y, the fitting protruding portion2C1that is provided in the side surface2C of the first frame2X fits over the protruding portion4A1within the fitting recessed portion2C2, so that the outer peripheral edge portion4A of the second spring4is secured to the side surface2C of the frame2.

The first weight5that is connected to the first spring3and the second weight6that is connected to the second spring4are disposed coaxially, and a recessed portion5A that is able to contain some or all of the second weight6is formed in the first weight5along the axial direction (the direction of the axis O), and an opening6A is formed in the center portion of the second weight6.

Given this, a magnet portion7that protrudes in the axial direction (the direction of the axis O) is provided in the first weight5, and a coil8is provided coiled around the magnet portion7in the second weight6. The magnet portion7is connected to the center portion of the first weight5, where a pair of magnets7A and7B, which are magnetized along the axial direction (the direction of the O axis) are connected in mutually opposing directions through a central yoke7C. The coil8is attached within an opening6A in the second weight6, and a back yoke9is disposed on the outer periphery of the coil8.

In such a vibration actuator1, application of the driving current to the coil8causes a driving force along the axial direction (the direction of the axis O) to act as an attractive force or repellent force between the magnet portion7and the coil8, causing the weight5and the weight6to produce a vibration in the axial direction. Power is supplied to the coil8through a flexible substrate10, where movable terminals of the flexible substrate10are connected to terminal portions of the coil8, and the stationary end of the flexible substrate10is connected to an input terminal portion2B1that extends out from the bottom face2B of the frame2.

Here a driving current is applied to the coil8at a first resonant frequency f1, which is set by the spring constant of the first spring3and the mass of the first weight5, or at a second resonant frequency f2, which is set by the spring constant of the second spring4and the mass of the second weight6. Through this, when a driving current of the first resonant frequency f1is applied, the first weight5side will vibrate with a large amplitude, and when a driving current with the second resonant frequency f2is applied, the second weight6side will vibrate with a large amplitude.

The vibration actuator1is able to apply two types of vibration sensations through the proper use of the driving current with the first resonant frequency f1and the driving current with the second resonant frequency f2. At this time, if the difference between the first resonant frequency f1and the second resonant frequency f2is set so as to be large, then it will be possible to produce effectively different vibration sensations.

A distinctive feature of this vibration actuator1is that the elements for setting the first resonant frequency f1and the second resonant frequency f2are independent. That is, the first spring3that supports the first weight5and the second spring4that supports the second weight6are connected mutually independently to the frame2. Through this, it is possible to set the first resonant frequency f1and the second resonant frequency f2with a high degree of freedom.

Moreover, in the example in the figure, the first frame2X and the second frame2Y are separate, enabling the first spring3, the first weight5, and the magnet portion7to be connected to the first frame2X side, and the second spring4, the second weight6, the coil8, and the flexible substrate10to be connected to the second frame2Y side, with the first frame2X and the second frame2Y connected together thereafter. This enables easy assembly. Moreover, in the example in the figures, a recessed portion5A that is recessed in the direction of the axis O (the direction of vibration) is provided in the first weight5, configured such that the second weight6will be contained within the recessed portion5A at the time of vibration, thus enabling effective vibration to be carried out while suppressing the thickness in the direction of vibration.

FIG. 3depicts a mobile information terminal100as an example of a mobile electronic device that is provided with a vibration actuator1according to an embodiment according to the present invention. The mobile information terminal100that is equipped with the vibration actuator1is able to produce vibrations that have different sensations depending on the type of signal that is sent, or depending on differences in information carried by the signal (for example, differences in callers, differences in levels of urgency, or the like). This makes it possible to convey information through the effective vibrations. Because the vibration sensations are different depending on the type of signal produced by the mobile information terminal side, this enables effective skin sensory feedback (haptics), such as in touch operations, and the like.

While embodiments according to the present invention were described in detail above, referencing the drawings, the specific structures thereof are not limited to these embodiments, but rather design variations within a range that does not deviate from the spirit and intent of the present invention are also included in the present invention. Moreover, insofar as there are no particular contradictions or problems in purposes or structures, or the like, the technologies of the various embodiments described above may be used together in combination.