JP7560876B2 - Artificial muscle actuator and its operating method - Google Patents

Description

The present invention relates to an artificial muscle actuator and its actuation method.

Artificial muscle actuators (see, for example, Patent Document 1) are used for purposes such as driving a wearable walking assistance device or power assist device. The artificial muscle actuator has an elastic tubular portion facing the pressure chamber, and a restraining member that restrains the elastic tubular portion so that the elastic tubular portion is deformed in the axial direction by the fluid in the pressure chamber.

International Publication No. WO 2008/140032

Conventional artificial muscle actuators such as those described above are excellent in terms of light weight, high output, and high flexibility, but there is room for improvement in terms of responsiveness.

The present invention aims to provide an artificial muscle actuator with excellent responsiveness and a method for operating the same.

The artificial muscle actuator of the present invention is an artificial muscle actuator having an elastic cylindrical portion facing a combustion chamber, an ignition device that ignites a mixture of fuel and air in the combustion chamber, and a restraining member that restrains the elastic cylindrical portion so that the elastic cylindrical portion deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the restraining member restrains the elastic tubular portion so that the elastic tubular portion contracts and deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the restraining member has a braided tubular portion formed by braiding multiple elongated bodies.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator having a group of elongated bodies in which the restraining member is formed of a plurality of elongated bodies each extending in the axial direction and aligned in the circumferential direction.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the restraining member is provided radially outward from the elastic tubular portion.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the restraining member is embedded in the elastic tubular portion.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the saturated vapor pressure of the fuel is 1 MPa or less.

In the above configuration, the artificial muscle actuator of the present invention is preferably an artificial muscle actuator in which the fuel contains dimethyl ether.

The artificial muscle actuator operation method of the present invention includes an ignition step of igniting a mixture of fuel and air in a combustion chamber facing the elastic cylindrical portion, and a restraint step of restraining the elastic cylindrical portion with a restraint member so that the elastic cylindrical portion is deformed in the axial direction by the expansion of the combustion gas in the combustion chamber.

The present invention provides an artificial muscle actuator with excellent responsiveness and a method for operating the same.

FIG. 1 is a conceptual diagram showing an artificial muscle actuator according to one embodiment of the present invention. 1 is a graph showing the results of a displacement response experiment in an example. 1 is a graph showing the results of a contractile force response experiment in an example.

The following describes an embodiment of the present invention with reference to the drawings.

The artificial muscle actuator 1 according to one embodiment of the present invention shown in FIG. 1 has an elastic cylindrical portion 3 facing the combustion chamber 2, an ignition device 4 that ignites the mixture of fuel and air in the combustion chamber 2, and a restraining member 5 that restrains the elastic cylindrical portion 3 so that the elastic cylindrical portion 3 is deformed in the axial direction by the expansion of the combustion gas in the combustion chamber 2.

More specifically, the restraining member 5 restrains the elastic tube portion 3 so that the elastic tube portion 3 is contracted and deformed in the axial direction by the expansion of the combustion gas in the combustion chamber 2. In FIG. 1, the two-dot chain line indicates the artificial muscle actuator 1 in the state before actuation, and the solid line indicates the artificial muscle actuator 1 in the state after actuation.

In this embodiment, the direction along the central axis O of the elastic tubular portion 3 is referred to as the axial direction, the direction along the straight line perpendicular to the central axis O is referred to as the radial direction, and the direction going around the central axis O is referred to as the circumferential direction.

The elastic tube portion 3 may be cylindrical about the central axis O, or may be a tube other than a cylindrical shape (e.g., an elliptical tube or a rectangular tube). The inner peripheral surface of the elastic tube portion 3 faces the combustion chamber 2. The elastic tube portion 3 is made of rubber or elastomer.

In this embodiment, the artificial muscle actuator 1 has two cover members 6 that are respectively fixed to both axial ends 3a of the elastic cylinder portion 3. One end 3a of the elastic cylinder portion 3 is fixed to one cover member 6, and the other end 3a of the elastic cylinder portion 3 is fixed to the other cover member 6. Therefore, the radial deformation of both ends 3a is restrained by the corresponding cover member 6. Each cover member 6 faces the combustion chamber 2.

In this embodiment, the ignition device 4 is provided on one of the cover members 6. The ignition device 4 can be, for example, a spark plug. The ignition device 4 is provided in the combustion chamber 2.

In this embodiment, the restraining member 5 has a braided tubular portion formed by braiding a number of elongated bodies. In addition, in this embodiment, the restraining member 5 is provided radially outward from the elastic tubular portion 3. Therefore, the artificial muscle actuator 1 is a McKibben type. With this configuration, the restraining member 5 can restrain the elastic tubular portion 3, causing the axial middle portion of the elastic tubular portion 3 to expand radially outward (see the hollow arrow in FIG. 1), while causing the elastic tubular portion 3 to contract in the axial direction (see the thick arrow in FIG. 1).

However, the artificial muscle actuator 1 is not limited to the McKibben type, and may be, for example, an axial fiber reinforced type. That is, the artificial muscle actuator 1 may be an axial fiber reinforced type artificial muscle actuator 1 in which the restraining member 5 has a group of elongated bodies formed of a plurality of elongated bodies each extending in the axial direction and arranged in the circumferential direction, and the group of elongated bodies is embedded in the elastic tubular portion 3. Even with this configuration, the restraining member 5 can restrain the elastic tubular portion 3 so that the elastic tubular portion 3 contracts and deforms in the axial direction as the axial middle portion of the elastic tubular portion 3 expands and deforms radially outward. That is, the restraining member 5 can restrain the elastic tubular portion 3 so that the elastic tubular portion 3 contracts and deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber 2.

The configuration for creating a state in the combustion chamber 2 that contains an air-fuel mixture is not particularly limited. The configuration may be such that the air-fuel mixture is introduced into the combustion chamber 2, or such that fuel and air are introduced separately into the combustion chamber 2. When the configuration is such that fuel and air are introduced separately into the combustion chamber 2, the fuel may be introduced in a liquid state or in a gaseous state.

The saturated vapor pressure of the fuel is preferably 1 MPa or less. With this configuration, it is easier to reduce the size and weight of the container for storing the fuel.

The fuel preferably contains dimethyl ether. This configuration ensures excellent environmental compatibility. The saturated vapor pressure of dimethyl ether is 0.62 MPa, which satisfies the above condition of 1 MPa or less.

The artificial muscle actuator 1 may have one or more vents that communicate between the inside of the combustion chamber 2 and the external space, which is the space outside the artificial muscle actuator 1. The location of the one or more vents is not particularly limited, and may be provided, for example, in the elastic tube portion 3 or in the lid member 6. The one or more vents may be configured to constantly communicate between the inside of the combustion chamber 2 and the external space, or may be configured to open when the pressure in the combustion chamber 2 reaches a predetermined value or higher to communicate between the inside of the combustion chamber 2 and the external space. With this configuration, after the artificial muscle actuator is operated by the combustion gas, the combustion gas can be passively discharged to the external space through one or more vents by the pressure of the combustion gas, making it possible to eliminate the need for a configuration or control for actively discharging the combustion gas from the combustion chamber 2.

According to the artificial muscle actuator 1 of this embodiment, the artificial muscle actuator 1 can be operated by deforming the elastic tube portion 3 in the axial direction due to the expansion of the combustion gas, so excellent responsiveness can be obtained. In other words, the time required from the input for starting operation (ignition by the ignition device 4) to the start of operation can be shortened.

The artificial muscle actuator actuation method according to one embodiment of the present invention is a method for actuating the artificial muscle actuator 1 according to the embodiment described above.

The artificial muscle actuator operation method according to this embodiment includes an ignition step in which a mixture of fuel and air is ignited in the combustion chamber 2 facing the elastic tubular portion 3, and a restraint step in which the elastic tubular portion 3 is restrained by the restraint member 5 so that the elastic tubular portion 3 is deformed in the axial direction by the expansion of the combustion gas in the combustion chamber 2.

More specifically, the restraining step is a step in which the elastic cylindrical portion 3 is restrained by the restraining member 5 so that the elastic cylindrical portion 3 is contracted and deformed in the axial direction due to the expansion of the combustion gas in the combustion chamber 2.

According to the artificial muscle actuator operation method of this embodiment, the artificial muscle actuator 1 can be operated by deforming the elastic tube portion 3 in the axial direction by the expansion of the combustion gas, thereby achieving excellent responsiveness.

The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the invention.

Therefore, the artificial muscle actuator 1 and its operating method according to the above-described embodiment can be modified in various ways, for example as described below.

The artificial muscle actuator 1 according to the embodiment described above can be modified in various ways as long as it is an artificial muscle actuator 1 that has an elastic tubular portion 3 facing the combustion chamber 2, an ignition device 4 that ignites the mixture of fuel and air in the combustion chamber 2, and a restraining member 5 that restrains the elastic tubular portion 3 so that the elastic tubular portion 3 deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber 2.

For example, the artificial muscle actuator 1 according to the embodiment described above may be an artificial muscle actuator 1 in which the restraining member 5 restrains the elastic tubular portion 3 so that the elastic tubular portion 3 is stretched and deformed in the axial direction by the expansion of the combustion gas in the combustion chamber 2. In this case, the restraining member 5 may have, for example, an annular body centered on the central axis O, or may have a group of annular bodies formed of a plurality of annular bodies arranged in the axial direction, each of which forms an annular shape centered on the central axis O. By using the restraining member 5 to restrain the elastic tubular portion 3 from deforming in the radial direction by the expansion of the combustion gas in the combustion chamber 2, the axial stretching and deformation of the elastic tubular portion 3 can be promoted.

In addition, the artificial muscle actuator 1 according to the embodiment described above is preferably an artificial muscle actuator 1 in which, in the above configuration, the restraining member 5 restrains the elastic tube portion 3 so that the elastic tube portion 3 contracts and deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber 2.

In addition, in the above-described configuration, the artificial muscle actuator 1 according to the embodiment is preferably an artificial muscle actuator 1 in which the restraining member 5 has a braided tubular portion formed by braiding multiple elongated bodies.

In addition, the artificial muscle actuator 1 according to the embodiment described above is preferably an artificial muscle actuator 1 having a group of elongated bodies in which the restraining member 5 is formed of a plurality of elongated bodies each extending in the axial direction and aligned in the circumferential direction.

In addition, the artificial muscle actuator 1 according to the above-described embodiment is preferably an artificial muscle actuator 1 in which the restraining member 5 is provided radially outward from the elastic tube portion 3 in the above configuration.

In addition, the artificial muscle actuator 1 according to the above-described embodiment is preferably an artificial muscle actuator 1 in which the restraining member 5 is embedded in the elastic tube portion 3 in the above configuration.

In addition, it is preferable that the artificial muscle actuator 1 according to the above-mentioned embodiment is an artificial muscle actuator 1 in which the saturated vapor pressure of the fuel is 1 MPa or less in the above configuration.

In addition, in the artificial muscle actuator 1 according to the embodiment described above, it is preferable that the artificial muscle actuator 1 in the above configuration is an artificial muscle actuator 1 in which the fuel contains dimethyl ether.

The artificial muscle actuator operation method according to the above-mentioned embodiment can be modified in various ways as long as it is an artificial muscle actuator operation method that includes an ignition step of igniting a mixture of fuel and air in the combustion chamber 2 facing the elastic tubular portion 3, and a restraint step of restraining the elastic tubular portion 3 with a restraint member 5 so that the elastic tubular portion 3 is deformed in the axial direction by the expansion of the combustion gas in the combustion chamber 2.

For example, the artificial muscle actuator operation method according to the above-mentioned embodiment may be a method for operating an artificial muscle actuator 1 other than the artificial muscle actuator 1 according to the above-mentioned embodiment.

An artificial muscle actuator as shown in Figure 1 was created, and a displacement response experiment and a contraction force response experiment were carried out. In both experiments, dimethyl ether was used as fuel, and a mixture with a specified air-fuel ratio was introduced into the combustion chamber and then ignited by an ignition device.

In the displacement response experiment, only one of the lid members was fixed and ignited, and the displacement response time was measured, which is the time it takes from the time of ignition until the axial displacement of the other lid member (i.e., the axial contraction of the elastic cylinder wall) begins. The results are shown in Figure 2. The "displacement" curve shown in Figure 2 shows the measured displacement of the other lid member. The "pressure" curve shown in Figure 2 shows the measured pressure inside the combustion chamber. As shown in Figure 2, the displacement response time was 0.029 seconds. Note that the time 0 seconds shown in Figure 2 is the time of ignition.

In the contraction force response experiment, both lid members were fixed and ignited, and the contraction force response time was measured, which is the time it takes from the time of ignition until the axial contraction force of the elastic cylinder wall is generated. The results are shown in Figure 3. The "contraction force" curve shown in Figure 3 shows the measured value of the contraction force. The "pressure" curve shown in Figure 3 shows the measured value of the pressure inside the combustion chamber. As shown in Figure 3, the contraction force response time was 0.015 seconds. The time 0 seconds shown in Figure 3 is the time of ignition.

For comparison, a contractile force response experiment was conducted using a conventional artificial muscle actuator that operates by opening a valve to introduce compressed air into a pressure chamber. The time it took from the time the valve was opened until a contractile force in the axial direction of the elastic cylinder wall was generated was 0.354 seconds.

Reference Signs List 1 Artificial muscle actuator 2 Combustion chamber 3 Elastic cylinder portion 3a End portion 4 Ignition device 5 Restraint member 6 Lid member O Central axis

Claims (4)

an elastic cylindrical portion facing the combustion chamber;
an ignition device for igniting a fuel and air mixture in the combustion chamber;
a restraining member that restrains the elastic cylindrical portion so that the elastic cylindrical portion contracts and deforms in the axial direction due to the expansion of the combustion gas in the combustion chamber;
having
The restraint member has a braided tubular portion formed by braiding a plurality of elongated bodies, and is provided radially outward of the elastic tubular portion . The artificial muscle actuator according to claim 1 , wherein the saturated vapor pressure of the fuel is 1 MPa or less. The artificial muscle actuator according to claim 1 or 2 , wherein the fuel contains dimethyl ether. an ignition step of igniting a mixture of fuel and air in a combustion chamber facing the elastic tube portion;
a restraining step of restraining the elastic tubular portion by a restraining member so that the elastic tubular portion contracts and deforms in an axial direction due to expansion of the combustion gas in the combustion chamber;
having
The restraining member has a braided tubular portion formed by braiding a plurality of elongated bodies, and is provided radially outward of the elastic tubular portion .

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