JP2004316713A - Actuator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an actuator which materializes cost and weight reductions. <P>SOLUTION: An actuator 1 is equipped with a piston 3 and a cylinder 2, either of which is provided with core 33. The other is provided with a coil 32 outputting in accordance with a position of the core 33. While the core 33 is provided to the piston 3, the coil 32 is provided to the cylinder 2. The core 33 is also mounted in the piston 3 brought closer to an inside peripheral surface of the cylinder 2. In some cases, the core 33 is provided to a part sandwiched by a piston ring. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an actuator, and more particularly, to an actuator that facilitates miniaturization and can reduce cost.
[0002]
[Prior art]
2. Description of the Related Art In general, various types of actuators used for fuel control and the like of an aircraft jet engine are known, and for example, an actuator that converts hydraulic pressure or air pressure into linear motion is known. Such an actuator needs to accurately measure a displacement amount of a device to be attached, and for that purpose, a position of a piston is accurately detected.
[0003]
Conventionally, as a device for detecting the piston position of such an actuator, a device in which an LVDT (Linear Variable Differential Transformer) is incorporated in a piston rod portion has been proposed. In addition, there has been proposed an LVDT in which the LVDT is attached to the tip of a rod, that is, outside the actuator. Here, the LVDT is a sensor called a differential transformer, which converts a mechanical linear displacement into an electric signal, and detects the linear displacement of the piston by assembling it into a rod or attaching it to the tip of the rod. Is what you can do.
[0004]
[Problems to be solved by the invention]
By the way, in the above-mentioned conventional actuator, when the LVDT is incorporated in the rod portion of the piston, the rod diameter of the piston is inevitably determined due to the size restriction required by the LVDT, so that downsizing, that is, downsizing, is required. There was a problem that it was difficult. In addition, when the LVDT is mounted outside the actuator, it is necessary to consider environmental resistance. Therefore, the number of parts is increased in order to take countermeasures, and management costs, assembly costs, disposal costs, and other life cycle costs are increased. There was a problem. In addition, since the number of components increases when externally mounted, there is a problem in that the relative position of each component, the difference in thermal expansion coefficient, and the like are accumulated, and the reliability of the piston position is reduced.
[0005]
The present invention has been made in view of such circumstances, and has as its object to provide an actuator that can be reduced in size. Another object of the present invention is to provide an actuator capable of reducing costs for management and assembly. Another object of the present invention is to provide an actuator capable of improving the reliability of the piston position.
[0006]
[Means for Solving the Problems]
In order to achieve the above object, the present invention proposes the following means.
The invention according to claim 1 is an actuator including a piston and a cylinder, wherein one of the piston and the cylinder is provided with a core part, and the other is a coil part that outputs according to the position of the core part. Is provided.
According to the actuator of the present invention, when the piston is displaced relative to a certain reference position of the cylinder, the displacement is output to the coil unit. Therefore, the relative position between the piston and the cylinder can be detected. In this case, since it is not necessary to incorporate the LVDT, the number of parts can be reduced, and the cost can be reduced. Further, the weight can be reduced.
[0007]
According to a second aspect of the invention, in the actuator according to the first aspect, the core portion is provided on the piston, and the coil portion is provided on the cylinder.
ADVANTAGE OF THE INVENTION According to the actuator which concerns on this invention, it becomes possible to arrange | position a coil in the stroke range of a piston, ie, the movement range of a core part. Therefore, the relative position between the piston and the cylinder can be accurately detected. That is, the reliability of the piston position can be improved.
[0008]
According to a third aspect of the present invention, in the actuator according to the second aspect, the core portion is provided on the piston in a state close to an inner peripheral surface of the cylinder.
ADVANTAGE OF THE INVENTION According to the actuator which concerns on this invention, it becomes easy to increase the area of the core part orthogonal to the longitudinal direction of a cylinder. When the area of the core portion increases, the number of magnetic fluxes also increases, so that the relative position between the piston and the cylinder can be accurately and reliably detected.
[0009]
According to a fourth aspect of the present invention, in the actuator according to the third aspect, the core portion is provided at a portion sandwiched between piston rings.
ADVANTAGE OF THE INVENTION According to the actuator which concerns on this invention, the damage of a core part by the property and pressure of a working fluid is prevented. Therefore, the durability of the piston can be improved.
[0010]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic sectional view showing an embodiment of the present invention.
In FIG. 1, an actuator 1 includes a cylinder 2 into which oil or air (working fluid) is guided, a piston 3 that slides in the cylinder 2 by hydraulic pressure or air pressure, and a cover 4 that covers an end of the cylinder 2. Is provided.
[0011]
A secondary coil 32 a, a primary coil 32 c, and a secondary coil 32 b are sequentially provided from one end to the other end on the inner surface side of the side peripheral portion of the cylinder 2. Is composed. The secondary coil 32a, the primary coil 32c, and the secondary coil 32b are wound with wires so that their respective axes are the same as the axis of the cylinder 2, and the secondary coil 32a and the secondary coil 32b are When viewed along the axial direction of the cylinder 2, it is wound so as to advance from one end to the other while rotating in the same direction around the axis.
[0012]
The primary coil 32c is connected to the AC power supply 21, and the secondary coils 32a and 32b are connected to the digital converter 22. At this time, the other end of the secondary coil 32a and the other end of the secondary coil 32b are connected. FIG. 2 schematically shows this state. The AC power supply 21 outputs a current to the primary coil 32c, and the digital converter 22 converts a potential difference input from the secondary coils 32a and 32b into a digital signal. The primary coil 32c generates an internal magnetic field when a current is applied by the AC power supply 21, and the secondary coils 32a and 32b change the magnetic flux density penetrating the inside, so that a voltage is applied to both ends. V _a, the _{V B} are those which generate respectively.
[0013]
A rod 5 is integrally attached to a piston 3 of the piston 3. The outer diameter of the piston 3 is formed to be slightly smaller than the inner diameter of the cylinder 2, and a concave portion 3 a formed along the circumferential direction and a step portion 3 b formed in an L-shape are formed on the side peripheral portion. Are provided. An O-ring (piston ring) 3c formed in a torus shape is provided in the concave portion 3a, and a core portion 33 formed in an annular shape is attached to the step portion 3b.
[0014]
The O-ring 3 c is made of, for example, an elastic member or a metal member, and separates a space on both sides of the piston 3 in the cylinder 2 by contacting an outer peripheral portion thereof with an inner peripheral surface of the cylinder 2. The core portion 33 is made of a ferromagnetic material, and its outer peripheral portion is formed close to the cylinder 2 so as to have a gap between itself and the inner peripheral portion of the cylinder 2. The core 33 generates a high magnetic flux density based on the magnetic field generated by the primary coil 32c.
[0015]
The cover 4 is made of a thick plate-like member, and includes a head cover 4 a that covers one end of the cylinder 2 and a rod cover that covers the other end and movably holds the rod 5. 4b. The head cover 4a and the rod cover 4b are provided with thick cylindrical protrusions 6a and 6b fitted to the cylinder 2 at the center portions thereof, and the outer peripheral side 4 of the protrusions 6a and 6b. At the corner, an insertion hole 7 through which the support rod 8 can be inserted is formed. The cover 4 (4a, 4b) is fitted to the end of the cylinder 2 in a state where the piston 3 is accommodated in the cylinder 2, and the cover 4 and the cylinder 2 are inserted through the insertion hole 7. A support rod 8 having a threaded portion is integrated by being tightened with a nut 9.
[0016]
A supply port 10a is formed in the head cover 4a so that oil or air is supplied into the cylinder 2 from outside. The rod cover 4b is formed with a hole 11 having a diameter larger than the outer diameter of the rod 5 and capable of moving the rod 5 inside, so that oil or air is supplied from the outside into the cylinder 2 through the hole 11. A supply port 10b is formed to be supplied. At the end of the rod cover 4b opposite to the cylinder 2, a metal guide 12 communicating with the hole 11 to guide the sliding of the rod 5 and a sealing member 13 for sealing between the outside and the cylinder 2 are provided. Have been.
[0017]
In the actuator 1 having the above-described configuration, when oil or air is supplied from the supply ports 10a and 10b, the pressure is changed from a higher pressure to a lower pressure in accordance with the pressure difference between the oil and air guided to both end surfaces of the piston 3. The piston 3 moves toward it. At this time, if a current is supplied to the primary coil 32c from the AC power supply 21, a magnetic field is generated inside the primary coil 32c by electromagnetic induction. The high magnetic flux density is generated in the core portion 33 through the magnetic field, in accordance with a change in the magnetic flux density generated in the core unit 33, mutual induction by the secondary coil 32a, the induced voltage V _A across the 32 _b, V _B Respectively occur.
[0018]
Generated induced voltage _V A, _{V B} are both secondary coil 32a, is input as a difference _V A -V _B of induced voltage 32b to digital converter 22, where it is converted into a digital signal, for example, it is incorporated to the computer The voltage value is converted as the displacement of the piston 3 via a program or the like. At this time, the displacement of the difference V _A -V _B and the piston 3 of the induced voltage, and has a relationship as shown in FIG. 3, the horizontal axis represents the displacement of the core portion 33, the vertical axis represents the difference _V A -V _B of the induced voltage (and the voltage _V A, _{V B).} As can be seen, the displacement of the difference V _A -V _B and the core portion 33 of the induced voltage (a point indicated by 0 in figure represents the reference position) origin and has a proportional relationship in the vicinity. (However, as the core displacement increases, it tends to gradually deviate from this proportional relationship.)
[0019]
Here, the relationship between the two is proportional because the coils 32a and 32b are wound in such a manner. Conversion is easy. The reason why the induced voltage V _A, is V _B varies according to the position of the core portion 33 is because there is a difference in magnetic permeability having magnetic permeability and portions other than the core portion 33 having a core portion 33, When the magnetic flux density of the core part 33 located inside the secondary coils 32a and 32b changes, the magnitude of the amplitude of the voltage generated in the secondary coils 32a and 32b differs according to the position of the core part 33. Because.
[0020]
According to the above configuration, the coil part, which is a component of the LVDT, is provided on the cylinder 2, which is a component of the actuator 1, and the core 33, which is a component of the LVDT, is provided on the piston 3 which is a component of the actuator 1. Therefore, there is no need to increase the diameter of the rod 5 of the piston 2, and downsizing, that is, downsizing can be achieved. Further, since the LVDT is not externally mounted, the number of parts can be reduced, and as a result, management costs, assembly costs, disposal costs, and other life cycle costs can be reduced. Also, since no extra parts are attached, errors in the piston position due to differences in the relative positions of the parts and differences in the coefficient of thermal expansion due to this are reduced, and the reliability of the piston position can be improved. Further, it becomes easy to increase the area of the core portion 33 orthogonal to the longitudinal direction of the cylinder. When the area of the core portion 33 increases, the number of magnetic fluxes also increases, so that the relative position between the piston 3 and the cylinder 2 can be accurately and reliably detected.
[0021]
In the above-described embodiment, the secondary coil 32a, the primary coil 32c, and the secondary coil 32b are arranged in this order from one end to the other end of the cylinder 2, but the winding of these coils 32a to 32c is performed. The wire structure (how to wind and arrange the coils) may be variously combined so that displacement can be detected, similarly to the known LVDT.
[0022]
Further, in the above embodiment, although the secondary coil 32a and the secondary coil 32b has been configured to be input to the digital converter 22 as a difference V _A -V _B of the induced voltage is connected to the opposite phases these coils 32a, 32b is induced voltage V _a are connected to the positive _phase, as V _B is inputted individually to the digital converter 22 may be configured such that subtraction postprocessing.
[0023]
Further, in the above-described embodiment, the core portion 33 is provided on the rod 5 side in the outer peripheral portion of the piston 3. However, as shown in FIG. And O-rings 3 c may be provided on both sides of the core 33. In FIG. 4, only the positional relationship and the number of the core 33 and the O-ring 3c are different from those in the above-described embodiment. Other parts have the same configuration and are denoted by the same reference numerals. In this configuration, since the oil or air guided into the cylinder 2 does not contact the core 33, the core 33 does not receive pressure from the oil or air, and is less affected by the properties of the working fluid. Therefore, damage to the core portion 33 can be suppressed, and the durability of the piston 2 can be improved.
[0024]
【The invention's effect】
As described above, according to the first aspect of the invention, when the piston is relatively displaced with respect to a certain reference position of the cylinder, the displacement is output to the coil unit. Therefore, the relative position between the piston and the cylinder can be detected. At this time, since it is not necessary to incorporate the LVDT, it is possible to reduce costs for management and assembly, and to reduce the size.
According to the second aspect of the present invention, it is possible to dispose the coil in the stroke range of the piston, that is, in the movement range of the core. Therefore, the relative position between the piston and the cylinder can be accurately detected. That is, the reliability of the piston position can be improved.
According to the third aspect of the invention, it is easy to increase the area of the core portion orthogonal to the longitudinal direction of the cylinder. When the area of the core portion increases, the number of magnetic fluxes also increases, so that the relative position between the piston and the cylinder can be accurately and reliably detected.
According to the fourth aspect of the present invention, since the working fluid does not contact the core, the core does not receive pressure from the working fluid, and is less affected by the properties of the working fluid. Therefore, the relative position between the piston and the cylinder can be detected with higher accuracy, and the durability of the piston can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an actuator according to an embodiment of the present invention.
FIG. 2 is a schematic diagram illustrating a relationship between a coil unit and a core unit of the actuator according to the embodiment of the present invention.
FIG. 3 is a graph showing a relationship between a piston displacement using an actuator according to an embodiment of the present invention and an induced voltage generated in a coil portion.
FIG. 4 is a schematic sectional view showing an actuator according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Actuator 2 Cylinder 3 Piston 32 Coil part 33 Core part

Claims (4)

In an actuator including a piston and a cylinder,
An actuator, wherein a core portion is provided in one of the piston and the cylinder, and a coil portion that outputs an output according to the position of the core portion is provided in the other. The actuator according to claim 1,
The actuator, wherein the core portion is provided on the piston, and the coil portion is provided on the cylinder. The actuator according to claim 2,
The actuator, wherein the core is provided on the piston in a state of approaching an inner peripheral surface of the cylinder. The actuator according to claim 3,
The actuator, wherein the core is provided at a portion sandwiched between piston rings.

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