JPH0695207A - Diaphragm - Google Patents

Abstract

PURPOSE:To eliminate the need for a position detecting element and to miniaturize a device by connecting a positional detection circuit with a damping coil as a position detecting means and differentiating the output of the circuit so that it is fed back to a driving coil control circuit. CONSTITUTION:An ac voltage generated in the damping coil 15 is detected as the position signal of a rotor (permanent magnet 2) by a signal detection circuit system in accordance with a change in a mutual inductance between a magnetic material piece 63 and the damping coil 15. The speed of the rotor 2 is controlled by differentiating the position signal and feeding it back to a control amplifier 25 for a driving coil 14 as a speed signal. Thus, the need of making the damping coil 15 function as a speed detecting means is eliminated, and also, the need of setting Hall element as the position detecting means is eliminated, so that the number of pins for a connector are reduced, and then, the packaging area can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a diaphragm device used for optical equipment such as video cameras.

[0002]

2. Description of the Related Art The structure of a conventional diaphragm device is shown in FIGS. In FIGS. 6 and 7, reference numeral 1 is a rotary shaft of an electromagnetic actuator for driving the diaphragm blades, 2 is a permanent magnet fixed to the rotary shaft 1 (a rotor of the actuator for driving the diaphragm blades), 5
Is a yoke that forms a magnetic circuit with the permanent magnet 2, 6 is a coil frame in which the braking coil 15 of the actuator and the drive coil 14 of the actuator are mounted, and 7 is the drive coil 14
A terminal board to which the coil terminals of the braking coil 15 are connected, and 8 is provided with guide pins 8b and 8c for guiding the diaphragm blades 11 and 12, and a diaphragm opening 8a, and holds the rotating shaft 1 rotatably. The blade case, 9 is fixed to the rotary shaft 1 at the central portion, and the diaphragm blades 11 and 12 are pivotally attached to pins 9a and 9b projecting from both ends of the blade case.
It is a case back, which is fixed to. Linear grooves 12b and 11b, through which guide pins 8b and 8c are slidably inserted, are formed in the diaphragm blades 11 and 12, respectively. Reference numeral 16 designates a bearing case that holds the rotary shaft 1 rotatably and is fixed to the blade case 8 together with the coil frame 6 and the yoke 5 by screws 8d. Reference numeral 14 designates a drive coil that applies a rotational force to the permanent magnet 2 by energizing it. Reference numeral 15 denotes a braking coil that detects the rotating speed of the permanent magnet 2 and brakes the permanent magnet 2, and 17 is inserted into the groove portion 6a of the coil frame 6 and fixed with tape or the like, and the rotation direction of the permanent magnet 2 Hall element, which detects the position of.

In the above arrangement, the Hall element 17 detects an arbitrary position during the opening / closing operation of the diaphragm blade. (Because the permanent magnet 2 is magnetized so that the magnetic flux density passing through the Hall element 17 changes depending on the position of the permanent magnet 2, the position of the diaphragm blade is detected by the output voltage of the Hall element 17.) The speed of the opening / closing operation of the blades of the device is detected by the braking coil 15. That is, when the permanent magnet 2 is rotated, a voltage is induced in the braking coil 15, and information on the speed of the diaphragm blade can be obtained from the magnitude of the induced voltage.

FIG. 8 is a diagram showing a control circuit of an actuator of the above-mentioned conventional diaphragm device. In the figure, 4
Reference numeral 0 denotes an operational amplifier (hereinafter abbreviated as an operational amplifier) that constitutes an inverting amplifier circuit for controlling the voltage applied to the drive coil 14, and forms an inverting amplifier circuit together with the feedback resistor 27, the resistor 28, and the variable resistors 37 to 39. I am configuring. Reference numeral 36 denotes a diaphragm control signal generated from a camera control circuit or an exposure control circuit provided in an optical device such as a video camera. The signal control circuit 36 amplifies the signal 36 and applies it to the drive coil 14 to rotate the rotor of the actuator. (That is, the permanent magnet 2) is rotated.

The above-mentioned braking coil 15 is connected to the non-inverting input terminal of the operational amplifier 40 and the resistor 28, and the induced voltage induced in the coil 15 according to the rotating operation of the permanent magnet 2 (the rotational speed of the permanent magnet 2 is increased). The proportional voltage) is fed back to the operational amplifier 40. Further, the induced voltage generated in the braking coil 15 causes a magnetic field in the opposite direction to the magnetic field generated by the driving coil 14, so that the permanent magnet 2 is braked.

The above-mentioned Hall element 17 is arranged at a position facing the magnetized surface (that is, the outer peripheral surface) of the permanent magnet 2 in order to detect the instantaneous rotation position (rotational phase) of the permanent magnet 2. An output is generated in response to a change in the magnetic field due to the movement of the magnetized surface of the permanent magnet 2 when the rotor 2 is rotated about the rotary shaft 1.

FIG. 9 shows a circuit connected to the hall element 17 as an instantaneous position detecting element of the permanent magnet 2 (rotor). In the figure, 41 is a Hall element 17
Is an operational amplifier that constitutes a Hall element driving circuit for driving the Hall element with a constant current. The output terminal of the operational amplifier 41 is connected to the drive current input terminal a of the Hall element 17, and the inverting input terminal of the operational amplifier 41 is the Hall element 17. It is connected to the drive current output terminal b and is connected in parallel to the ground resistance 46. Variable resistors 43 to 45 are connected to the non-inverting input terminal of the operational amplifier 41, and the variable resistors 43 to 45 are adjusted so that the current flowing from the operational amplifier 41 to the hall element 17 is always constant.

Reference numeral 42 is an operational amplifier which constitutes a differential amplifier for detecting the output voltage of the hall element 17.
Op-amp 42, feedback resistor 52, and resistors 50 and 5
1 and the variable resistors 47 to 49 configure the differential amplifier. This differential amplifier has a function of removing the in-phase component from the voltage output generated from the output voltage terminals c and d of the Hall element 17 to obtain a true output (an output representing a magnetic field change due to the rotation of the permanent magnet 2). There is. The inverting input terminal of the operational amplifier 42 is connected to one output voltage terminal d of the hall element 17 via the resistor 51, and the non-inverting input terminal of the operational amplifier 42 is connected to the other output voltage terminal c of the hall element 17 via the resistor 50. It is connected.

When the permanent magnet 2 rotates about the rotary shaft 1, a change in the magnetic field with respect to the Hall element 17 due to the permanent magnet 2 occurs, and a voltage output is output to the output voltage terminals c and d of the Hall element 17 due to the change in the magnetic field. This voltage output is input to a camera control circuit or an exposure control circuit (not shown) after the in-phase component is removed by a differential amplifier including an operational amplifier 42. The camera control circuit or the exposure control circuit detects the stop position and the rotation angle of the rotor (permanent magnet 2) based on the output of the operational amplifier 42, and the stop position and the rotation angle detect the opening degree of the diaphragm device. The operation amount is determined and the driving of the operational amplifier 40 is determined.

[0010]

The diaphragm device having the above-mentioned conventional structure has the following drawbacks because the position detection and the speed detection are detected by separate detecting means.

(1) When connecting the braking coil, the driving coil, and the hall element to the circuit, an 8-pole connector is required, which is disadvantageous to the recent high-density mounting.

(2) If the diaphragm device is miniaturized, position detecting elements such as Hall elements cannot be mounted.

An object of the present invention is to provide a diaphragm device which solves the above problems without increasing the number of parts.

[0014]

According to the present invention, in order to realize the downsizing of the diaphragm device, the braking coil 15 is used as a position detecting means, a position detecting circuit is connected to the coil 15, and the output of the position detecting circuit is It is characterized in that the Hall element as the position detecting means, which is required in the conventional diaphragm device, is eliminated by differentiating and feeding back to the drive coil control circuit. In the diaphragm device of the present invention shown in the following examples,
In order to superimpose an AC signal on the voltage applied to the drive coil of the actuator while attaching the magnetic material piece to a position (end surface) different from the magnetized surface (outer peripheral surface) of the rotor (permanent magnet) of the diaphragm blade drive actuator Connected to the drive operational amplifier for controlling the drive coil, and detects the AC voltage generated in the braking coil according to the change in mutual inductance due to the approach and separation of the magnetic material piece and the braking coil. Signal detection circuit system (for example, high-pass filter, AC amplifier, rectifier circuit, low-pass filter, offset adjusting amplifier, dynamic range adjusting amplifier) connected to the braking coil, and the input of the driving amplifier for controlling the driving coil. A differentiating circuit for differentiating the output of the signal detecting circuit system is connected to the terminal. That is, in the diaphragm device of the present invention, an AC voltage generated in the braking coil according to a change in mutual inductance between the magnetic material piece and the braking coil is applied to the rotor (permanent magnet 2) by the signal detection circuit system. Since the position signal is detected, and the position signal is differentiated and fed back to the control amplifier of the drive coil as a speed signal to control the speed of the rotor, it is not necessary to use the braking coil as a speed detecting means. Further, it is no longer necessary to install a hall element as a position detecting means.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A diaphragm device as an embodiment of the present invention will be described below with reference to the drawings. Since the present invention is not in the mechanical structure of the diaphragm device but in the control system of the diaphragm blade driving actuator, the description of the mechanical structure other than the actuator is omitted unless it is necessary.
Further, also in the electrical configuration, the same components as those of the conventional device are indicated by the same reference numerals as those in FIGS. 8 and 9, and the description thereof will be omitted.

FIG. 1 shows an embodiment of a control circuit for an electromagnetic actuator used in the diaphragm device of the present invention. In addition, in FIG. 1, description of the components indicated by the same reference numerals as those in FIGS. 8 and 9 is omitted. In FIGS. 3 and 4, 63 and 64 are magnetic material pieces, which are fixed to both end surfaces of the permanent magnet 2 by adhesion or the like.

In the present invention, in order to detect an arbitrary position of the opening / closing operation of the diaphragm device, the magnetic material pieces 6 are provided on both end surfaces of the permanent magnet 2.
Since 3 and 64 are provided, the mutual inductance between the drive coil 14 and the braking coil 15 changes depending on the arbitrary stop position of the permanent magnet 2, and the inductance change is detected as the output of the braking coil 15.

The magnetic material piece 63 and the magnetic material piece 64 may have the same shape. The positional relationship between the drive coil 14 and the braking coil 15 of the magnetic material piece 63 and the magnetic material piece 64 is as shown in FIG. 2, for example. FIG. 2C shows a state in which the diaphragm device is fully opened, and FIG. 2B shows a state in which it is fully closed. If the magnetic material piece 64 at this time is placed in the same phase as the magnetic material piece 63, the change in mutual inductance between the drive coil 14 and the braking coil 15 from the fully opened to the fully closed state of the diaphragm device can be made larger. The same effect can be obtained even if the positional relationships among the magnetic material pieces 63 and 64, the drive coil 14, and the braking coil 15 are reversed by 180 °. The change in mutual inductance with respect to the rotation angle of the permanent magnet 2 can be changed linearly or non-linearly by arbitrarily changing the shape of the magnetic material piece.

Next, the configuration of FIG. 1 will be described. Figure 1
In FIG. 2, reference numeral 25 is an operational amplifier, the amplification degree of which is determined by fixed resistors 28 and 29, and the drive coil 14 is controlled by a control signal 36.
Supply power to. An AC oscillator 26 supplies an AC signal to the drive coil 14 in addition to the DC component. The AC component supplied to the drive coil 14 by the AC oscillator 26 is set to a frequency at which the permanent magnet 2 cannot respond, and the voltage amplitude and frequency are constant. 18 is an AC oscillator 2
6 is a high-pass filter for detecting the AC component supplied to the drive coil 14 at 6 and generated in the braking coil 15 by mutual induction. Reference numeral 19 is an AC amplifier that amplifies the AC component detected by the high-pass filter 18, and 20 is a rectifier circuit. Reference numeral 21 is a low-pass filter for further smoothing the output of the rectifier circuit 20 to direct current, and 22 and 23 are operational amplifiers, which are amplification circuits composed of fixed resistors 29, 30, 31, 33, 35 and variable resistors 32, 34. The output of the low-pass filter 21 can be adjusted to an appropriate signal level, and the output signal of the operational amplifier 23 can be used as position information. 24 is a differentiating circuit, which is an operational amplifier 23
Of the output change of the operational amplifier 2
The speed can be controlled by connecting 5 so that negative feedback is applied.

FIG. 2 shows the input waveform of the drive coil 14 and the output waveform of the braking coil 15. FIG. 2 (b) shows the throttle device fully closed and FIG. 2 (c) shows the throttle device fully open. Show. As can be seen in FIG. 2, the position of the magnetic material piece 63 and the output of the braking coil 15 in FIGS. 2B and 2C are shown from the experimental results. Reference numeral 53 is a composite wave synthesized by the AC oscillator 26 into a DC component, 54 is an output waveform of the braking coil 15 when the diaphragm device is fully closed, and 55 is an output waveform of the braking coil 15 when the diaphragm device is fully open. .

[0021]

As described above, according to the present invention, the position detecting element is not required, which is advantageous for downsizing the diaphragm device. Further, since the position detecting element is unnecessary, the number of pins of the connector can be reduced and the mounting area can be reduced.

[Brief description of drawings]

FIG. 1 is a diagram showing an electrical configuration of an actuator of a diaphragm device to which the present invention is applied.

2A is an input waveform of a drive coil 14 in the configuration of FIG. (B) is the braking coil 1 when the expansion device is fully closed.
Output waveform of 5. (C) is an output waveform of the braking coil 15 when the expansion device is fully opened.

FIG. 3 is a sectional view of a diaphragm device of the present invention.

FIG. 4 is a front view of the diaphragm device of the present invention.

FIG. 5A is a partial front view of the diaphragm device of the present invention when it is fully opened. (B) is a front view of a part of the diaphragm device of the present invention when it is fully closed.

FIG. 6 is a cross-sectional view of a conventional diaphragm device.

FIG. 7 is a front view of a conventional diaphragm device.

FIG. 8 is a schematic diagram of a control circuit of an actuator of a conventional diaphragm device.

FIG. 9 is a schematic diagram of a position detection system of a conventional diaphragm device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotating shaft 14 ... Drive coil 2 ... Permanent magnet 15 ... Braking coil 63 ... Magnetic material piece 16 ... Bearing case 64 ... Magnetic material piece 17 ... Hall element 5 ... Yoke 18 ... High pass filter 6 ... Coil frame 19 ... AC amplifier 7 ... Terminal board 20 ... Rectifier circuit 8 ... Blade case 21 ... Low-pass filter 9 ... Arm lever 10 ... Base plate 24 ... Differentiating circuit 11 ... Aperture blade 26 ... AC oscillator 12 ... Aperture blade 22, 23, 25, 40, 41, 42 ... Operational amplifier 32, 34, 38, 44, 48 ... Variable resistor 13 ... Bearing case 36 ... Control signal 27, 28, 29, 30, 31, 33, 35, 37, 3
9,43,45,46,47,49,50,51,52
… Fixed resistance

Claims (2)

[Claims] 1. A rotor made of a cylindrical permanent magnet in which an S pole and an N pole are magnetized on the outer peripheral surface, a driving coil arranged to face the outer peripheral surface of the rotor, and the rotor are separated from each other. In a diaphragm device including an electromagnetic actuator having a braking coil arranged at a position facing the driving coil and a driving circuit for applying a driving voltage to the driving coil, A piece of magnetic material that spreads in a direction intersecting with the magnetized area on the outer peripheral surface of the rotor is attached to the end surface of the rotor, and an AC oscillator for applying an AC signal to the drive coil is provided on the input side of the drive circuit. A position signal detection circuit, which is provided and detects a rotor position signal from a mutual inductance change between the braking coil and the magnetic material piece when the rotor rotates, is connected to the braking coil. Slight To throttle device, wherein a differentiating circuit for applying to the input of the driver circuit is connected between the input terminal of the output terminal and the drive circuit of the position detection circuit. 2. The diaphragm device according to claim 1, wherein the position detection circuit includes a high-pass filter, an AC amplifier, a rectifier, a low-pass filter, and the like.