JPH0313802A - Method for judging position of iron core of solenoid - Google Patents

Abstract

PURPOSE:To detect the positions of iron cores without using a special detector by detecting the ratio between AC voltages which are applied to two driving coils. CONSTITUTION:The linking point of a pair of driving coils 4 and 5 is grounded through a resistor R. When transistors Tr1 and Tr4 or Tr2 and Tr3 are conducted, a DC power source +B for excitation is applied to the driving coils 4 and 5 in the reverse direction, and iron cores are driven. Capacitors C1 and C2 are provided in parallel with the driving coils 4 and 5. An AC power source Vx is applied to the central point between the capacitors C1 and C2. The difference between the AC voltages generated at a point A and a point B is obtained with a differential amplifier circuit 15. In this way, an AC bridge is formed, and the difference between the impedances of the driving coils 4 and 5 is obtained. Since the impedances of the driving coils 4 and 5 are changed in response to the positions of the iron cores, the positions of the iron cores can be obtained in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for determining the iron core position of a bistable solenoid.

(Prior Art and Problems to be Solved) Solenoids have advantages such as quick response, simple configuration, and miniaturization, and are used as actuators in many devices. The solenoid has one coil and a return spring, and when the coil is energized, the iron core is attracted and moved by electromagnetic force against the spring force, and when it is deenergized, the spring is released. It has a monostable solenoid that returns the iron core to its original position using a spring force, a set of coils, and one permanent magnet, and the magnetic force of the permanent magnet allows one end of the iron core to be moved to either side of the casing. The iron core is held by suction at one end, and when the iron core is moved to the other end, the coil is energized, and after moving to the other end in cooperation with the permanent magnet, the coil is deenergized, and the magnetism of the permanent magnet is again turned off. There is a type of bistable solenoid that attracts and holds an iron core at the other end using force.

When a bistable solenoid is used in an automatic control device or the like, it is necessary to determine in which position the iron core of the solenoid is located.

Conventionally, as a method for determining the position of the iron core of such a bistable solenoid, for example, a laser is emitted onto both ends of the iron core, and the reflected light is detected to determine the presence or absence of the ends of the iron core, i.e., A laser position sensor is used to detect the position of the iron core.

However, such a laser position sensor is not only very expensive, but also difficult to miniaturize, and especially when used in small automatic equipment, there is a problem in that space is difficult.

The present invention has been made in view of the above-mentioned points, and an object of the present invention is to provide a method for determining the position of the iron core of a solenoid, which allows the position of the iron core to be easily determined without using a special position sensor. do.

(Means for Solving the Problems) In order to achieve the above object, the present invention includes a casing formed of a magnetic member, an iron core movably disposed on the axis of the casing, and an abbreviation of the casing. A permanent magnet is placed in the center and attracts and holds one end of the iron core to the casing, and a permanent magnet is placed on both sides of the permanent magnet and is connected in series with both ends connected to an excitation power source to cooperate with the permanent magnet when energized. An AC excitation power source is connected to the connection end of each of the coils to the excitation power source via a capacitor, respectively, of a solenoid equipped with a set of coils that act to drive the iron core. The electric potential difference between the connection points is detected, a voltage signal with a polarity corresponding to the difference is obtained, and the position of the iron core is determined based on the voltage signal.

(Function) When the coil is deenergized, one end surface of the iron core is attracted to one end surface of the casing by the magnetic force of the permanent magnet, and the other end surface is separated from the other end surface of the casing with a gap. In this state, the magnetic resistance of one half of the iron core that is attracted to the casing is smaller than the magnetic resistance of the other half, and the magnetic permeability in the coil on the negative side is higher than the magnetic permeability of the coil on the other side. is also large, the magnitude of the inductance of a coil is proportional to the magnetic permeability within the coil, and therefore the inductance of the coil on one side of the iron core is greater than the inductance of the coil on the other side, resulting in an alternating current The voltage (divided voltage) at the connection point between the negative side coil and the capacitor due to the excitation power source is higher than the voltage at the connection point between the other side coil and the capacitor. Therefore, the position of the iron core is determined by detecting the difference between these voltages and obtaining a voltage signal with a polarity corresponding to the magnitude thereof.

(Example) An embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 shows a bistable solenoid to which the present invention is applied, and the solenoid 1 includes a casing 2 formed of a magnetic member and also serving as a yoke, and a permanent magnet 3 disposed approximately in the center of the casing 2. , a set of coils 4.5 are arranged along the axial direction on both the left and right sides of this permanent magnet 3, and the axes of these permanent magnets 3 and each coil 4.5 are loosely fitted, and axially It is composed of a movable iron core 6.

The permanent magnet 3 has an outer surface and an inner surface each having a magnetic pole, one magnetic pole is in contact with the inner surface of the casing 2 and is magnetically connected, and the other magnetic pole is opposed to the iron core 6 with a slight gap. .

For convenience of explanation, the iron core 6 is 6a on the left side from the center.

Let the right side be 6b. The iron core 6 is configured such that an end surface 6a' on the left side 6a or an end surface 6b' on the right side 6b can selectively abut against either the opposing end surface 2a or 2b of the casing 2, and the end surface on the left side When 6a' is in contact with the end surface 2a of the casing 2, the right end surface 6b' is separated from the end surface 2b of the casing 2 by a predetermined distance d; The left end surface 6a'' is spaced apart from the end surface 2a of the casing 2 by a predetermined distance Md. Further, a rod (not shown) formed of a non-magnetic member such as a stainless steel member is fixed to the axis position of one or both end faces 6a' and 6b' of the iron core 6. It can be connected to automatic equipment.

FIG. 2 shows a drive circuit 10 and an iron core position determination circuit 11 for the solenoid L, and the drive circuit 10 includes four transistors T.
It is equipped with ri to Tr4. Transistors Tri and Tr
3 connects each emitter to power supply B and each base to the control circuit (
(not shown), each collector is connected to a transistor Tr2 and a transistor Tr2.
4 collectors. Transistor Tr2
and T'4, each emitter of which is grounded, and each base of which is connected to the control circuit.
Diodes D1 to D4 are connected between the emitters and collectors of ri to Tr4.

Coils 4 and 5 of the solenoid 1 are connected in series, one end of the coil 4 is connected to the connection point a between the collector of the transistor Tri and the collector of the transistor Tr2, and one end of the coil 5 is connected to the connection point a between the collector of the transistor Tr3 and the collector of the transistor Tr4. The other ends are connected to each other and grounded via a resistor R. These coils 4.5 are formed to have the same electrical characteristics.

AC excitation power supply circuit (oscillation circuit) 12 of the position discrimination circuit 11
The output terminal of is connected to the connection points a, b and the phase shift circuit 13 via capacitors CI and C2. This AC excitation power supply circuit 12 outputs an AC voltage (8) with a low frequency of about 300 Hz. Further, the capacitors C1 and C2 have the same capacitance. The output voltage x of the excitation power supply circuit 12 is applied to the comparator I4 via the phase shift port ll513. The comparator 14 forms a sampling pulse P based on the input voltage VX.

A connection point A between the capacitor C1 and the coil 4 is connected to an input terminal of the differential amplifier circuit 15, and a connection point B between the capacitor C2 and the coil 5 is connected to one input terminal of the differential amplifier circuit 15. The differential amplifier circuit 15 has potentials VA and V at connection points A and B.
, and a voltage signal VC having a phase and magnitude corresponding to the difference between the two is output and applied to the sample and hold circuit 16.

The output of this sample-and-hold circuit 16 is smoothed through a low-pass filter 17 and applied to a comparator 18 as a DC voltage (2o).

The action will be explained below.

As shown in FIG. 1, the end face 6a' of the iron core 6 of the solenoid 1
is attracted to the end surface 2a of the casing 2, and the end surface 6b'
are spaced apart from the end surface 2b, and the DC magnetic flux Φ, , Φ2 due to the permanent magnet 3 is assumed to be flowing as shown by the dotted line. In this state, the magnetic resistance R1 on the left side 6a of the iron core 6
is smaller than the magnetic resistance R2 on the right side 6b (R1<R,
), and each transistor Tri-Tr of the drive circuit lO
4 is off and coils 4.5 are both deenergized.

On the other hand, the output voltage vx of the AC excitation power supply circuit 12 is applied to the coil 4.5 via the capacitors CI and C2.
The voltages VA and Vs at connection points A and B are the voltage divisions between capacitor C1 and coil 4 of voltage ■8, and capacitor C2 and coil 5, and the inductance of coil 4.5 is ZLI, ZL.
When each impedance of I, capacitor CI, and C2 is Zc, it is expressed by the following formula.

VA-Vx (ZLl+R) / (ZC+ZL, +
R)...(1) Vm -VW (ZL*+R)/ (Zc +Z
L! +R)...(2) Inductance of coil 4.5 Z L I % Z L
* is proportional to the magnitude of the magnetic permeability μ, μ° within these coils 4.5. As mentioned above, the magnetic resistance R8 of the iron core 6a in the left coil 4 is the same as that of the iron core 6b in the right coil 5.
The magnetic permeability μ of the left side 6a of the iron core 6 is larger than the magnetic permeability μ of the right side 6b (μ〉μ゛).As a result, the inductance Z of the coil 4
LI is larger than the inductance ZL1 of the coil 5 (ZLl>ztt), and the voltage Va at connection points A and B (7)
, Vm is from the above formulas (1) and (2) D, V4 > Vm
(Fig. 3 (b), (C)), the differential amplifier 15 outputs a signal VC (Fig. 3 (d)) according to the difference (VA-■,) between the input voltage vA and ■6. do.

Incidentally, the capacitors CI and C2 cooperate with the coil 4.5 to divide the excitation voltage V and also have the function of cutting the DC component.

The phase shift circuit 13 is a comparator 1 that adjusts the phase of the output voltage V of the excitation power supply circuit 12 to be as close to the phase of the output voltage VC of the differential amplifier circuit 15 as possible, and outputs the adjusted phase.
4 compares the voltage V manually inputted from the phase shift circuit 13 with a threshold value vN set to a value slightly smaller than the approximate peak value of the voltage vx, and outputs an open signal of V,>V. Then, a sampling pulse P (FIG. 3(a)) is formed. This sampling pulse P is synchronized with the period of the voltage v8, and its timing is controlled by the differential amplifier circuit 15 by the phase shift circuit 13.
The output voltage is set approximately near the peak value of the output VC (FIG. 3(c)).

The sampling hold circuit 16 holds and outputs the peak value +VCP of the voltage vc input from the differential amplifier circuit 15 using the sampling pulse P input from the comparator 14. This positive output voltage +VCP is smoothed through a low-pass filter 17 and output as a DC voltage +Vl (FIG. 3(e)). The comparator 18 is
This voltage +■. Enter each darkness value (+V, □, +V,
lsm) compared to +■llll1〈+v,ku+v,1
．． 8, it is determined that the iron core 6 of the solenoid 1 is in the left position as shown in FIG.

Next, when switching the iron core 6 of the solenoid 1 from the left side to the right side as shown in FIG. 1, transistors Tr3 and Tr2 of the drive circuit 10 (FIG. 2) are turned on. As a result,
From power supply 1B to transistor Tr3 → coil 5 → coil 4
Excitation current flows through the path of →transistor Tr2 →ground and the path of coil 5 →resistance R →ground, and coils 5 and 4 are energized. The resistor R is connected in parallel with the coil 4.

The magnetic flux Φ generated in the right side coil 5 by this excitation current is in the same direction as the DC magnetic flux Φ flowing on the right side 6b of the iron core 6, and is added to the DC magnetic flux Φ. As a result, iron core 6
More magnetic flux flows to the right side 6b of the figure, and the magnetic flux density increases accordingly, and the attractive force toward the right in the figure becomes thicker.
On the other hand, the direction of the magnetic flux Φ11 generated in the left coil 4 is opposite to the DC magnetic flux Φ1 flowing through the left side 6a of the iron core 6, and acts to cancel the DC magnetic flux Φ. At this time, the value of the resistance R should be set so that the magnitude of the magnetic flux Φ11 caused by the coil 4 is approximately the same as the magnitude of the DC magnetic flux Φ1! Ji! ff
Then, the excitation current of the coil 4 is adjusted. As a result, the magnetic flux on the left side 6a of the iron core 6 becomes approximately O, and accordingly, the magnetic flux density becomes approximately 0, and the attractive force of the iron core 6 also becomes approximately 0. As a result, the iron core 6 rapidly moves rightward from the position due to the unbalanced force, the end surface 6a' separates from the end surface 2a of the casing 2, and the end surface 6b' moves away from the end surface 2b of the casing 2.
is adsorbed to.

The transistors Tr2 and Tr3 of the drive circuit 10 are turned off immediately after the end surface 6b' of the iron core 6 is attracted to the end surface 2b of the casing 2, and the coil 4.5 is deenergized. Therefore,
The magnetic flux inside the casing 2 is the DC magnetic flux Φ caused by the permanent magnet 3.
8, only Φ□, and the magnetic resistance R8 on the right side 6b of the iron core 6 is smaller than the magnetic resistance R on the left side 6a (R
1), the magnetic flux density on the right side 6b becomes larger than the magnetic flux density on the left side 6a. As a result, the end surface 6b' of the iron core 6 is attracted and held on the end surface 2b of the casing 2.

When the iron core 6 is switched from the left side position to the right side position in this way, the left side 6a
The magnetic resistance R1 of the right side 6b is thicker than the magnetic resistance R8 of the right side 6b (R1>Rx), and the magnetic permeability μ in the coil 4 is
As a result, the inductance ZLI of coil 5 is larger than the inductance ZLI of coil 4 (Zti>ZL+).
Therefore, the voltage v1 at the connection point B is higher than the voltage vA at the connection point A < (V, > VA) (Fig. 4(b)).
, (C)) The single dynamic amplifier 15 has these input voltages vA and ■
, the voltage VC (Figure 3 (
mountain) is output. At this time, the voltage ■. The phase of is shifted by 180 degrees with respect to the state jEl of the iron core 6 before movement (FIG. 3 (b)), and becomes a negative minimum value -VCP at the timing of generation of the sampling pulse P.

The sampling hold circuit 16 holds and outputs the negative peak value -Ver of the voltage vc input from the differential amplifier circuit 15 using the sampling pulse P input from the comparator 14. This output voltage -VCP is smoothed through a low-pass filter 17 and output as a DC voltage -vn (FIG. 4(e)).
Input this voltage -vo and set each threshold value (-V, □, VHst
), −■. , <-V, <-V. 1, it is determined that the iron core 6 of the solenoid 1 has been switched from the left position to the right position as shown in FIG.

In addition, when switching the iron core 6 of the solenoid 1 from the right-hand position to the original left-hand position, the drive circuit 10 (FIG. 2)
transistors Tri and Tr4 are turned on, and the coil 4 is turned on.
．． 5, the magnetic flux Φ4.5 generated by the left coil 4. is in the same direction as the DC magnetic flux Φ1 generated by the permanent magnet 3, and as a result, the magnetic flux density on the left side 6a of the iron core 6 becomes thicker (and the attractive force becomes very large).On the other hand, the magnetic flux Φ generated by the right side coil 5 is in the opposite direction to the DC magnetic flux Φ due to the permanent magnet 3, and accordingly, the right side 6b of the iron core 6
The magnetic flux density becomes very small, and the attractive force becomes approximately O.

As a result, the iron core 6 is attracted to the coil 4 side and rapidly moves to the left. The drive circuit 10 then immediately turns off the transistors Tri and Tr4 and deenergizes the coil 4.5. The iron core 6 is held by the permanent magnet 3 with its end surface 6a'' attracted to the end surface 2a of the casing 2.

Then, as mentioned above, the voltage vA at the connection point A becomes the voltage vA at the connection point B.
is higher than the voltage V□<(VA>Vs), and the DC voltage +vll is input to the comparator 18. The comparator 18, as described above, inputs the input voltage +vIl and the threshold value (
+V++at, +Vx*z) and +■
When the function □<+v, <+VHsm, it is determined that the iron core 6 has been switched from the right-hand position to the left-hand position.

In addition, if one of the coils 4.5, for example, the coil 4, is disconnected, the voltage vA at the connection point A becomes approximately the excitation voltage vx, which is significantly higher than the voltage at the connection point B.
(Va >> Vs), and as a result, the differential amplifier 1
As a result, the input voltage +V of the comparator 18 became higher than the normal input voltage +V (Fig. 3(e)), and the coil 5 was disconnected. In this case, the input voltage to the comparator 18 -■, ゛ becomes smaller than the normal input voltage -■ (Fig. 4(e))
.

Therefore, the comparator 18 input voltage +■o゛ or -y
, + with the threshold value +V++az or =v08, it is possible to determine whether the coil 4 or the coil 5 is disconnected. That is, the input voltage of the comparator 18 is +■.

'> + V When Het, coil 4 is disconnected,
When Ve'<Vllllll, it is determined that the coil 5 is disconnected.

Furthermore, when both coils 4.5 are disconnected, the voltages (1, 2) at the connection points A, , and B both become approximately the excitation voltage v8, and the output V of the differential amplifier circuit 15.

is approximately O. As a result, the input voltage ±v of the comparator 18 falls between the threshold value +vMs+ and -VMBI, and +VMIl>±Vms>-VHst.
Thereby, the comparator 18 determines that both coils 4 and 5 are disconnected.

(Effects of the Invention) As explained above, according to the present invention, there is provided a casing formed of a magnetic member, an iron core movably disposed on the axis of the casing, and an iron core disposed approximately in the center of the casing. A permanent magnet that attracts and holds one end of the casing to the casing, and a permanent magnet arranged on both sides of the permanent magnet and connected in series, with both ends connected to an excitation power source, respectively, and cooperates with the permanent magnet when energized to excite the iron core. An AC excitation power source is connected via a capacitor to the connection end of each of the coils to the excitation power source of a solenoid equipped with a set of coils to be driven, and the potential difference between each connection point between these coils and the capacitor is calculated. By detecting and obtaining a voltage signal with a polarity corresponding to the difference, and determining the position of the iron core based on the voltage signal, the position of the iron core of the solenoid can be easily determined without using a special position sensor, etc. This has the effect that the solenoid can be made smaller, and that it can also be placed in a narrow space where the equipment used is restricted.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a bistable solenoid to which the solenoid iron core position detection method according to the present invention is applied, and FIG. A block diagram showing one embodiment, FIGS. 3 and 4, are diagrams showing signal waveforms at various parts in the circuit of FIG. 2. 1... Solenoid, 2... Casing, 3... Permanent magnet, 4.5... Coil, 6... Iron core, IO...
- Drive circuit, 11... Position discrimination circuit, 12... AC excitation power supply circuit, 13... Phase shift circuit, 14.18...
Comparator, 15... Differential amplifier circuit, 16... Sample hold circuit, 17... Low pass filter.

Claims (1)

[Claims] A casing formed of a magnetic member, an iron core movably arranged on the axis of the casing, a permanent magnet arranged approximately in the center of the casing that attracts and holds one end of the iron core to the casing, and a permanent magnet. each of the coils of a solenoid comprising a set of coils arranged on both sides of the magnet and connected in series, both ends of which are connected to an excitation power source, respectively, and which cooperate with the permanent magnet to drive the iron core when energized; An AC excitation power source is connected to the connection end of the excitation power source through a capacitor, and the potential difference between each connection point between these coils and the capacitor is detected to obtain a voltage signal with a polarity corresponding to the difference. A method for determining the position of an iron core of a solenoid, characterized by determining the position of the iron core based on a voltage signal.