Patent Application
20070200653
This application claims benefit of priority under 35 USC § 119 to Japanese Patent Application No.2006-48587 filed on Feb. 24, 2006, the entire contents of which are incorporated by reference.
1. Field of the Invention
The present invention relates to an electromagnetic actuator which is used for various kinds of industrial equipment, such as a switching device and an industrial robot.
2. Related Art
The electromagnetic actuator is normally constituted by combining a magnet coil and a permanent magnet, where the magnet coil is energized to move a needle and then the magnet coil is non-energized to latch the needle at its moved position by absorption power of the permanent magnet.
In the shown state, a current larger than the current of the second magnet coil 105 is supplied to the first magnet coil 104, and so the number of magnetic fluxes 109 is larger than the number of magnetic fluxes 110. Therefore, the needle 106 is moved leftward by a leftward driving force. If the first magnet coil 104 and second magnet coil 105 are non-energized in this state, the needle 106 is latched at the shown position by the magnetic fluxes of the permanent magnet 103.
In the case of moving the needle 106 rightward, a current larger than the current of the first magnet coil 104 is supplied to the second magnet coil 105 so as to diminish the magnetic fluxes of the permanent magnet 103 and give a rightward driving force to the needle 106.
A stator 201 includes a frame member 202, a ring-shaped permanent magnet 203 fixed on the frame member 202 and a magnet coil 204 provided below the permanent magnet 203. A needle 205 includes a plunger member 206 provided to be vertically reciprocable inside the stator 201, a collar member 207 mounted at a top edge of the plunger member 206 and an axis member 208 supported by the plunger member 206.
In the state of
If the needle 205 descends as in the state of
In the case of moving the needle 205 upward from a latch position of
In both the above-mentioned first and second conventional examples, one magnet coil is used to perform two actions of diminishing the magnetic fluxes of the permanent magnet and giving the driving force to the needle in the case of moving the needle which is latched by the permanent magnet in an opposite direction. For that reason, the energization of the magnet coil is uniformly controlled so that the current passing through the coil becomes a certain level or higher.
Depending on the state of a load side, however, it is not always necessary to give a great driving force to the needle. It is possible to release the latch just by diminishing the magnetic fluxes of the permanent magnet and move the needle as-is in the opposite direction. Therefore, there is further room for improvement as to the above-mentioned conventional apparatuses from a perspective of effective utilization of energy.
An object of the present invention is to provide an electromagnetic actuator which can improve energy efficiency by varying how to energize a magnet coil according to a state of a load side.
To attain the object, the present invention provides an electromagnetic actuator of a first configuration which includes: a needle having an approximately cylindrical plunger member and a collar member mounted at a base thereof (of the plunger member) and provided to be reciprocable between a latch position and a latch release position inside a stator; a first magnet coil provided surrounding the plunger member and having sufficient electromagnetic power to put in a latch state the needle in a latch release state on energization; a permanent magnet having sufficient absorption power for absorbing the collar member of the needle put in the latch state by the electromagnetic power of the first magnet coil and maintaining the latch state even when the first magnet coil is non-energized; and a second magnet coil capable of diminishing magnetic fluxes of the permanent magnet and changing the needle from the latch state to the latch release state on energization.
In a second configuration, the stator of the first configuration includes: a first stator having the first magnet coil mounted thereon and capable of forming a magnetic path of the magnetic fluxes generated by the first magnet coil; and a second stator having the permanent magnet and the second magnet coil mounted thereon and capable of forming a magnetic path of the magnetic fluxes generated by the permanent magnet and the second magnet coil.
In a third configuration, the first stator of the second configuration includes an absorbing portion on which an absorbing surface for absorbing a head of the plunger member in the latch state is formed; and the position of the absorbing surface is deviated by a distance L2 from a center position of axial length L1 of the first magnet coil in a direction to be apart from the needle.
In a fourth configuration, a ratio between the distance L2 and the axial length L1 of the third configuration (L2/L1) is 10 to 30%.
In a fifth configuration, a concave portion for concentrating the magnetic fluxes is formed on at least one of the absorbing surface of the absorbing portion of the first stator and a contact surface of the head of the plunger member contacting the absorbing surface in the third or fourth configuration.
In a sixth configuration, surface area of the concave portion in the fifth configuration is 30% or more of the absorbing surface or the contact surface.
In a seventh configuration, a diameter of the concave portion in the fifth configuration is 30% or more of an outside diameter of the absorbing portion or the head.
In an eighth configuration, depth h2 of the concave portion in one of the fifth to seventh configurations is 3 mm or less.
In a ninth configuration, thickness t1 of the collar member in one of the first to eighth configurations is smaller than radial width h1 of an absorbing action surface on which the permanent magnet exerts an absorbing action to the collar member.
In a tenth configuration, a lightening portion is formed inside the plunger member in one of the first to ninth configurations.
In an eleventh configuration, sectional area of the lightening portion in the tenth configuration is 30% or more of the sectional area of the plunger member.
In a twelfth configuration, the diameter of the lightening portion in the tenth configuration is 30% or more of the outside diameter of the plunger member.
According to the present invention, the magnet coils are divided into the first magnet coils for giving a driving force to the needle and the second magnet coils for diminishing the magnetic fluxes of the permanent magnet. Therefore, it is possible to select energization or non-energization of the two magnet coils as appropriate according to the state of the load side so as to improve the energy efficiency.
The first stator 11 is composed of a pole piece 111 in a ring shape or a hollow cylinder shape with an opening 111a and an absorbing surface 111b formed thereon, a disk member 112 fixed on an upper end face of the pole piece 111 and having an opening 112a formed thereon, a cylinder member 113 fixed on a periphery side of a lower end face of the disk member 112, and a hollow member 114 fixed on the lower end face of the cylinder member 113. All the pole piece 111, disk member 112, cylinder member 113 and hollow member 114 are formed by a magnetic material.
The second stator 12 is composed of a cylinder member 121 fixed on the periphery side of the lower end face of the hollow member 114 and a hollow member 122 fixed on an inner periphery side of the lower end face of the hollow member 114 via a permanent magnet 4. The cylinder member 121 and hollow member 122 are also formed by the magnetic material. The permanent magnet 4 and the hollow member 122 are in a ring shape having the same radial width h1.
The needle 2 is composed of an approximately cylindrical plunger member 21 and a disk-shaped collar member 22, and an axis member 5 linked to the load side is mounted at a head center position of the plunger member 21. Thickness of the collar member 22 is t1, which is a value smaller than the radial width h1 of the permanent magnet 4. The plunger member 21 and the collar member 22 are also formed by the magnetic material.
A first magnet coil 31 is provided in a space formed between periphery surfaces of the pole piece 111 and plunger member 21 and an inner periphery surface of the cylinder member 113. A second magnet coil 32 is provided in a space at a position below the first magnet coil 31 and formed between the periphery surface of the plunger member 21 and the inner periphery surfaces of the hollow member 114, permanent magnet 4 and hollow member 122.
The first magnet coil 31 is primarily intended to give a driving force to the needle 2, and its current-carrying capacity is large. The second magnet coil 32 is primarily intended to diminish the magnetic fluxes of the permanent magnet 4 which are latching the needle 2 although it may also contributes to giving the driving force to the needle 2 in conjunction with the first magnet coil 31. Therefore, the current-carrying capacity of the second magnet coil 32 is smaller than that of the first magnet coil 31.
The upper end face of the head of the plunger member 21 opposed to the absorbing surface 111b of the pole piece 111 is a contact surface 21a, and a concave portion 21b of depth h2 is formed to be predetermined area on the contact surface 21a. To be more specific, absorption power “F” of the magnet is proportional to a square of magnetic flux density “B” as shown in a formula (1) below.
F=Bˆ2*A/μ0 (1)
In the formula (1), μ0 denotes space permeability and A denotes magnetic flux passage area. It is possible, by forming the concave portion 21b at the head of the plunger member 21, to concentrate the magnetic fluxes about to pass all over the head in the concave portion 21bTherefore, it is possible to increase the magnetic flux density “B” and intensify the absorption power “F.”
A lightening portion 21c is formed inside the plunger member 21, and an opening 22a is formed on the collar member 22 to continue from the lightening portion 21c. The lightening portion 21c and opening 22a are formed so as to render the needle 2 lightweight and allow many magnetic fluxes to pass through to the center of the needle 2 in a short time. In reality, operating time for the needle 2 to be in the latch state from the latch release state is approximately 0.2 seconds. In the case where the lightening portion 21c is not formed, operation is completed before the magnetic fluxes permeate around the center of the needle 2.
The first magnet coil 31 has axial length L1. And the absorbing surface 111b of the aforementioned pole piece 111 is formed at a position deviated by a distance L2 from the center position of the axial length L1 in a direction to be apart from the needle 2. According to this embodiment, a ratio between the distance L2 and the axial length L1 (L2/L1) is a predetermined value described later.
Next, a description will be given as to the operation of this embodiment configured as above. FIGS. 3 to 5 are explanatory diagrams schematically showing the respective magnetic flux distribution states of the first magnet coil 31, second magnet coil 32 and permanent magnet 4 in the case of moving the needle 2.
As shown in
Next, when the needle 2 moves to the position shown in
In the case of moving downward the needle 2 in the latch state as above, only the second magnet coil 32 is energized to diminish the magnetic flux Bm of the permanent magnet 4 by means of a magnetic flux Bc2 thereof as shown in
A conventional apparatus performed the energization for moving the needle 2 upward and the energization for releasing the latch of the needle 2 by using one magnet coil having large current-carrying capacity. As for the configuration of
However, the above operation of energization is just an example. In reality, it is possible, by considering conditions of the load side and other conditions, to select a combination of energization and non-energization for the two magnet coils as appropriate so as to precisely control the electromagnetic actuator according to circumstances.
In the state of
To realize the electromagnetic actuator of high efficiency, the inventors hereof performed trials and experiments by variously changing the values of various parameters indicated by symbols in
(1) When the ratio between the axial length L1 of the first magnet coil 31 and the distance L2 from the coil center position to the absorbing surface 111b thereof (L2/L1) was in the range of 10 to 30%, the direction of the magnetic flux was apt to become parallel with the axial direction so that great electromagnetic power (absorption power) could be obtained.
(2) It is desirable that surface area of the concave portion 21b at the head of the plunger member 21 be 30 to 90% of the entire area of the absorbing surface 111b (or the contact surface 21a). In the case of 30% or more, the magnetic flux density at the end of the concave portion 21b increases so that great absorption power can be obtained. In the case of 90% or more, however, the end of the concave portion 21b becomes magnetically saturated and so the absorption power is reduced on the contrary. In reality, a numeric value close to 90% should be adopted because it is desirable to have the absorption power to the extent of causing magnetic saturation. The same result can be obtained by rendering the diameter of the concave portion 21b 30 to 90% of an outside diameter of the absorbing surface 111b (or the outside diameter of the head).
(3) It is desirable that the depth h2 of the concave portion 21b be in the range of 0.5 to 3 mm. It is because working on the concave portion 21b becomes easier by rendering it 0.5 mm or more. If it exceeds 3 mm, it is not desirable because magnetic reluctance of the concave portion 21b increases and the absorption power obtained by the entire needle 2 is reduced.
(4) In the configuration of
(5) It is desirable that sectional area of the lightening portion 21c be 30 to 50% of the sectional area of the plunger member 21. It is because, while a weight saving effect of the needle 2 is weak in the case of less than 30%, the effect of increasing the magnetic flux density can be obtained in addition to the weight saving effect in the case of 30% or more. If it exceeds 50%, there is a danger that the needle 2 may become magnetically saturated. The same result can also be obtained by setting the diameter of the lightening portion 21c at 30 to 50% of the outside diameter of the plunger member 21.
(6) It is desirable that thickness t1 of the collar member 22 be smaller than the radial width h1 of an absorbing action surface on which the permanent magnet 4 exerts an absorbing action on the collar member 22. It is because the magnetic flux density can thereby be increased.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2006-048587 | Feb 2006 | JP | national |
