JPS6243429B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reciprocating drive actuator for reciprocating a driven body.

Conventionally, there is a reciprocating actuator as shown in FIG. 1 or 2, for example (see Japanese Utility Model Application Publication No. 56-35890).

First, the reciprocating drive actuator shown in FIG. 1 consists of a pair of bobbins 2 and 3 made of Bakelite wound in a cylindrical yoke 1 made of a soft magnetic material so that the same polarity occurs in adjacent parts. The cylindrical electromagnetic coils 4 and 5 are inserted into the pair of cylindrical electromagnetic coils 4 and 5, and the magnetic pole pieces 7 and 8 and the shafts 9 and 10 are integrated at both ends of the cylindrical magnet 6 which is magnetized in the axial direction. The movable element 11 is fixed to a movable member 11, its shafts 9 and 10 are supported by end plates 12 and 13, and the movable member 11 is disposed so as to be displaceable in the axial direction of the cylindrical electromagnetic coils 4 and 5.

In this reciprocating drive actuator, when the magnet 6 is magnetized with an N pole on the left side and an S pole on the right side as shown in the figure, the part adjacent to the electromagnetic coils 4 and 5 is the N pole, and both ends are the S pole. When an excitation current is applied, the N pole side of the magnet 6 attracts the S pole side of the electromagnetic coil 4, and the S pole side
Since they repel each other from the pole side, the movable element 11 is displaced to the left in the figure.

In addition, the portions adjacent to the electromagnetic coils 4 and 5 are S
When an excitation current with N poles at both ends is applied, the N pole side of the magnet 6 repels the N pole side of the electromagnetic coil 4, and the S pole side attracts the N pole side of the electromagnetic coil 5. The mover 11 is displaced to the right in the figure.

Next, the reciprocating drive actuator shown in FIG. 2 has two magnets magnetized in the radial direction at both ends of a cylindrical yoke 18, which has shafts 9 and 10 fixed to both ends, in a pair of electromagnetic coils 4 and 5. 19,2
A movable element 21 formed by fixing a movable element 0 is disposed so as to be displaceable in the axial direction, and the principle of displacement of the movable element 21 is the same as that shown in FIG.

In such conventional reciprocating drive actuators, when detecting minute displacements of the movable element, the movable core of the differential transformer is directly connected to the shaft, or a detection lever is fitted to the movable element to detect the eddy current method or the movable element. An inductance type detection sensor had to be attached externally.

However, detection accuracy of differential transformer, eddy current, or inductance type detection sensors deteriorates due to the influence of magnetic fields from electromagnetic coils, etc.
In order to detect with high precision, a magnetic shield or the like is required, which increases the size of the device.

In addition, when a detection lever is used, mechanical vibration is likely to occur, which may easily cause resonance with the control system.
There is a disadvantage that highly accurate displacement detection cannot be performed.

This invention was made in view of the above points, and an object of the present invention is to enable highly accurate detection of the amount of displacement of a movable element in a reciprocating drive actuator as described above, without increasing the size of the device. do.

Therefore, in the reciprocating drive actuator according to the present invention, a fixed electrode made of a conductor is provided on the inner peripheral surface side or the outer peripheral surface side of the pair of cylindrical electromagnetic coils, and a movable electrode facing the fixed electrode is provided on the outer peripheral surface of the movable element. ,
The amount of displacement of the movable element can be detected by detecting the change in capacitance between the fixed electrode and the movable electrode due to the displacement of the movable electrode due to the displacement of the movable element.

Embodiments of the present invention will be described below with reference to FIG. 3 and subsequent figures of the accompanying drawings. Note that portions corresponding to those in FIGS. 1 and 2 are designated by the same reference numerals, and explanations of those portions will be omitted.

FIG. 3 is a longitudinal sectional view showing an example of an axially magnetized reciprocating actuator embodying the present invention.

In this reciprocating drive actuator, a pair of cylindrical electromagnetic coils 4 and 5 are connected to cylindrical first and second fixed electrodes 31 made of a conductor formed into a bobbin shape,
32 and fitted into the yoke 1, and the first and second fixed electrodes 31,
A cylindrical movable electrode 3 made of a conductor facing 32
3 is inserted.

Terminals 34, 35 and 36 are connected to the first and second fixed electrodes 31 and 32 and the movable electrode 33, and the yoke 1 and the first and second fixed electrodes 31 and 33 are connected to terminals 34, 35 and 36, respectively.
32, an insulating film 37 for insulation is interposed. Note that the terminal 36 is connected so as not to affect the displacement of the movable electrode 33.

With this configuration, when the movable element 11 is displaced to the left in the figure, the opposing area between the first fixed electrode 31 and the movable electrode 33 becomes wider, and both electrodes 31, 3
While the capacitance between the second fixed electrode 32 and the movable electrode 33 becomes narrower, the capacitance between the two electrodes 32 and 33 becomes smaller.

On the other hand, when the movable element 11 is displaced to the right in the figure, the opposing area between the first fixed electrode 31 and the movable electrode 33 becomes narrower, and the capacitance between the two electrodes 31 and 33 becomes smaller. , the opposing area between the second fixed electrode 32 and the movable electrode 33 is increased, so that both electrodes 3
The capacitance between 2 and 33 increases.

In this way, depending on the displacement of the mover 11, the first
Since each capacitance between the second fixed electrodes 31, 32 and the movable electrode 33 changes, the amount of displacement of the movable element 11 can be detected by detecting the capacitance.

In this way, since the capacitive displacement sensor is integrated into the reciprocating drive actuator, the amount of displacement of the mover 11 can be detected with high precision without being affected by the magnetic field from the electromagnetic coils 4, 5, etc. There is no need for magnetic shielding, etc.

Further, in this embodiment, the members holding the inner peripheral surfaces of the electromagnetic coils 4 and 5 are connected to the first and second fixed electrodes 3.
1 and 32, the configuration is simpler than when a fixed electrode is provided separately.

FIG. 4 is a vertical cross section showing an example of a radial magnetization type reciprocating drive actuator according to the present invention, and FIG. Since it is the same as that, the same reference numerals are given and the explanation thereof will be omitted.

FIG. 5 is a block diagram showing an example of a control section of a reciprocating drive actuator embodying the present invention.

In the figure, a control circuit 40 inputs various parameters, for example, when this reciprocating drive actuator is used in an internal combustion engine, a signal Sn (n= ₁ ...n) indicating various operating parameters of the engine, and controls the driven object. The output signal of the arithmetic circuit 41 that calculates the specified position of
Do and the detection position signal Vo of the sensor circuit 42 that detects the position of the movable element 11 are input, and the excitation current of the electromagnetic coils 4 and 5 is applied via the drive circuit 43 so that the driven body is at the specified position. Control the mover 11
Displace.

FIG. 6 is a circuit diagram showing an example of the sensor circuit of FIG. 5.

In the figure, capacitors C ₁ and C ₂ are electrostatic capacitances between the first and second fixed electrodes 31 and 32 and the movable electrode 33 of the reciprocating drive actuator shown in FIG. 5, respectively.

These capacitors C ₁ and C ₂ are connected in series to form an AC bridge circuit 45 with resistors R ₁ and R ₂ , and an AC power source 46 is connected to points a and b of this AC bridge circuit 45 . AC voltage is applied. (Terminals 36, 34, and 35 in FIG. 5 correspond to points c, a, and b in FIG. 6, respectively.) The unbalanced voltage output from points c and d of this AC bridge circuit 45 is converted into a full-wave rectifier circuit. After full wave rectification with 47 and amplification with differential amplifier 48, the diode
A peak hold circuit 49 consisting of a resistor R ₃ , a resistor R 3 , and a capacitor C ₃ holds the peak value _, and outputs an analog voltage V ₀ via a buffer circuit 50 .

Here, the principle of detecting the amount of displacement of the movable element 11 will be explained.

In general, the capacitance C between two concentric cylindrical electrodes in a dielectric is determined by the dielectric constant of vacuum (8.85×10 ^-12
[F/m]) is εo, the dielectric constant is εs, the area of the electrode is S [m ² ], and the distance between the electrodes is d [m], then C=8.85×10 ^-12・εs・It is expressed as S/d [F].

In this circuit, the capacitance between the first fixed electrode 31 and the movable electrode 33 is _C1 , and the capacitance between the second fixed electrode 32 and the movable electrode 33 _{is C2.}
As such, it is inserted into one piece of the AC bridge circuit 45.

Therefore, the unbalanced voltage e output from this AC bridge circuit 45 is expressed as e=-KC ₁ -C ₂ /C ₁ +C ₂ ·Vs (K is determined by R ₁ and R _{2 )} , where Vs is the applied voltage. In this case, if the opposing distances between the first and second fixed electrodes 31 and 32 and the movable electrode 33 are respectively l ₁ and l ₂ (see Fig. 5), the unbalanced voltage e
The relationship between and the facing distances l ₁ and l ₂ is expressed as e=-Kl ₁ -l ₂ /l ₁ +l ₂ (l ₁ +l ₂ = constant).

Therefore, by determining the unbalanced voltage e, the amount of displacement of the movable element 11 can be obtained.

In addition, the output voltage in the sensor circuit in Fig. 6
An example of the relationship between Vo and the displacement amount of the mover 11 is shown in the seventh example.
It is shown in the figure.

Furthermore, the detection of each capacitance between the first and second fixed electrodes 31 and 32 and the movable electrode 33 can be performed, for example.
It is also possible to configure a CR oscillator to detect a change in frequency, or to configure a delay circuit to detect a change in delay time, and is not limited to the above detection method.

In addition, in the above embodiment, an example was described in which the fixed electrode is composed of first and second fixed electrodes that hold the inner peripheral surfaces of a pair of electromagnetic coils, but it is needless to say that the present invention is not limited to this. .

For example, the fixed electrode may be constituted by first and second fixed electrodes that hold each outer peripheral surface of a pair of electromagnetic coils, and one fixed electrode may be configured to hold one fixed electrode on the inner peripheral surface side of a pair of electromagnetic coils or The fixed electrode may be provided on the outer peripheral surface side, and the point is that the fixed electrode may be provided so that the capacitance changes depending on the displacement of the movable electrode accompanying the displacement of the movable element.

As explained above, according to the present invention, the capacitive displacement sensor is integrated into the reciprocating drive actuator, so the amount of displacement of the mover can be detected with high accuracy without increasing the size of the device. .

[Brief explanation of the drawing]

FIGS. 1 and 2 are longitudinal sectional views showing different examples of conventional reciprocating drive actuators. FIG. 3 is a longitudinal sectional view showing one embodiment of the present invention, FIG. 4 is a longitudinal sectional view showing another embodiment of the invention, and FIG.
The figure is a block diagram showing an example of the control section of the reciprocating drive actuator shown in Fig. 3, Fig. 6 is a circuit diagram showing an example of the sensor circuit, and Fig. 7 shows the output voltage Vo and displacement amount of the mover. FIG. 2 is a diagram showing an example of the relationship between 1... Yoke, 4, 5... Electromagnetic coil, 6, 1
9,20...Magnet, 7,8...Magnetic pole, 9,
10... Shaft, 11, 21... Mover, 18
... Cylindrical yoke, 31 ... First fixed electrode, 3
2... Second fixed electrode, 33... Movable electrode, 37
...Insulating film.

Claims (1)

[Claims] 1. A movable element including a permanent magnet is disposed so as to be displaceable in the axial direction within a pair of cylindrical electromagnetic coils wound so that the same polarity occurs in adjacent parts. In the reciprocating drive actuator, a cylindrical fixed electrode made of a conductive material is provided on the inner peripheral surface side or the outer peripheral surface side of the pair of electromagnetic coils, and a cylindrical fixed electrode made of a conductive material opposite to the fixed electrode is provided on the outer peripheral surface of the movable element. A reciprocating drive actuator characterized by having movable electrodes each having a shape. 2. The reciprocating drive actuator according to claim 1, wherein the fixed electrode comprises first and second fixed electrodes each holding the pair of electromagnetic coils.