JP3095567B2 - Electric diaphragm device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric diaphragm device configured to drive a diaphragm blade or a diaphragm mechanism by an electromagnetic actuator.

[0002]

2. Description of the Related Art An electric diaphragm device for driving a diaphragm blade or a diaphragm mechanism by an electromagnetic actuator is known. Hereinafter, the mechanical and electrical configuration of a known electric throttle device will be described with reference to FIGS. 5 and 6.

FIG. 5 is an exploded perspective view showing an electromagnetic actuator and a diaphragm blade driving mechanism of a conventionally known electric diaphragm device. In FIG. 5, reference numeral 1 denotes a rotor of the electromagnetic actuator, which is made of a permanent magnet having an N-pole region and an S-pole region formed on a surface thereof, and a shaft 5 protruding from an end surface. Reference numeral 3 denotes a drive coil for generating an electromagnetic force for rotating the rotor 1, and is fixedly arranged at a predetermined gap from the surface of the rotor. Reference numeral 2 denotes a braking coil that generates an induced voltage when the rotor 1 is rotated, and is fixedly disposed at a predetermined gap from the surface of the rotor 1. Numeral 4 denotes a magnetically responsive detection element such as a Hall element for detecting the rotational position of the rotor 1 when the rotor 1 is rotated, and is fixed to a mounting member (not shown) and has a predetermined position with respect to the outer peripheral surface of the rotor. They are arranged facing each other with a gap. Reference numeral 6 denotes a diaphragm blade drive lever that can rotate about the shaft hole 6c, and the shaft 5 of the rotor is inserted and fixed in the shaft hole 6c. Reference numerals 7 and 8 denote aperture blades, which are pivotally mounted on the lever 6 by pins 6a and 6b projecting from both ends of the drive lever 6, and are driven in the direction of the arrow in accordance with the rotation of the lever 6. Reference numeral 18 denotes a return spring that constantly urges the lever 6 in a counterclockwise direction (that is, the diaphragm blades 7 and 8 are in the diaphragm closing direction).

FIG. 6 is a schematic diagram showing a configuration of an electromagnetic actuator drive circuit of the electric diaphragm device. In the figure, 1 is the rotor, 2 is the braking coil, 3 is the drive coil, and 4 is the magnetically responsive detection element. An amplifier 23 is connected to the coil 3 as a drive circuit for applying a drive voltage to the coil, and an input terminal of the amplifier 23 receives a luminance signal 15 from an exposure control circuit 17 such as a video camera. It has become. The amplifier 23
Is composed of an operational amplifier 9, a feedback resistor 10 and a resistor 11, and the braking coil 2 is connected to a non-inverting input terminal of the operational amplifier 9 (hereinafter abbreviated as an operational amplifier) and the resistor 11. When the rotor 1 rotates, an induced voltage (a voltage proportional to the rotation speed of the rotor 1) is generated in the braking coil 2, and the induced voltage is negatively fed back to the operational amplifier 9, and the amplifier 23 is generated from the exposure control circuit 17. The speed of the rotor 1 is controlled by applying a drive voltage to the drive coil 3 in accordance with the difference between the luminance signal 15 and the induced voltage of the braking coil 2. Note that the induced voltage generated in the braking coil 2 generates a magnetic field in a direction opposite to the magnetic field generated by the driving coil 3, so that the rotor 1 is braked.

On the other hand, the above-mentioned magnetically responsive element 4 (generally a Hall element is used) outputs an output corresponding to a change in the magnetic field due to the movement of the magnetized surface of the rotor 1 when the rotor 1 is rotated. The output and the rotation position and amount of rotation of the rotor 1 are detected by a detection circuit (not shown) incorporated in the exposure control circuit 17 based on the output.

[0006]

The above-mentioned conventional electric throttle device has the following problems.

(A) In the above-described conventional diaphragm device, when opening and closing the diaphragm, a hysteresis of the operating load is mechanically generated in the direction in which the diaphragm blades are opened and closed, and therefore the voltage applied to the drive coil is also reduced. Hysteresis occurs in the opening and closing directions of the aperture.

For this reason, when the aperture is set to the small aperture state, hunting occurs in the aperture blade, and controllability of the aperture blade is deteriorated.

(B) When the aperture is in the small aperture state for the above-mentioned reason, hunting tends to occur, so that the operating speed of the aperture blades cannot be increased, and a high-speed aperture device cannot be realized.

An object of the present invention is to solve the above-mentioned problems inherent in the conventional apparatus, and to provide an electric diaphragm apparatus which does not cause hunting of the diaphragm blades and can operate at high speed.

[0011]

According to the present invention, there is provided an electric diaphragm device provided on an input side of a signal amplifier circuit for driving a driving coil.
An AC oscillator for applying an AC signal having an amplitude larger than a difference between an applied voltage for driving the aperture in the opening direction and an applied voltage for driving the aperture in the closing direction, and an output of the AC oscillator. And a control circuit for controlling, wherein an AC signal output from an AC oscillator is superimposed on a DC voltage applied to the drive coil.

[0012]

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a diaphragm device according to an embodiment of the present invention. Since the gist of the present invention is not in the mechanical structure of the diaphragm device but in the control system of the actuator for driving the diaphragm blades, the description of the mechanical structure other than the actuator is omitted as far as necessary. Also in the electrical configuration, the same components as those of the conventional device are denoted by the same reference numerals as those in FIGS. 5 and 6, and description thereof is omitted.

FIG. 1 shows an embodiment of a control circuit of an electromagnetic actuator used in the diaphragm device of the present invention.

In FIG. 1, an AC oscillator 12 supplies an AC signal to the drive coil 3 in addition to a DC component. The AC component supplied to the drive coil 3 by the AC oscillator 12 is set within a range in which the rotor 1 can respond. 13
Is an AC oscillator control circuit for controlling the output of the AC oscillator 12 (hereinafter abbreviated as OSC control circuit). The O
The SC control circuit 13 responds to a control signal 16 (a control signal output from a camera control circuit or an exposure control circuit 17 incorporated in a camera or the like as an aperture position) by the AC oscillator 1.
2 or the amplitude of the AC oscillator 12 can be changed by the control signal 16 in accordance with the position of the diaphragm. Reference numeral 14 denotes a low-pass filter which cuts off the AC component of the output of the braking coil 2 when an AC component applied to the drive coil 3 is induced in the braking coil 2.

FIG. 4 shows a waveform of a voltage applied to the drive coil 3 of the conventional diaphragm device. In the conventional diaphragm device, a hysteresis voltage 22 is generated in the drive coil applied voltage 19 during the opening direction operation and the drive coil applied voltage 20 during the closing direction operation due to an operation loss of the diaphragm blades or the like generated in the mechanism of the diaphragm device. 2, the drive coil applied voltage waveform of the aperture device of the present invention is an AC voltage superimposed waveform 21, and its amplitude is slightly larger than the hysteresis voltage 22, so that the hysteresis of the drive coil applied voltage at the time of opening and closing the aperture is almost zero. Will not occur.

It is desirable that the frequency of the AC component of the AC voltage superimposed waveform 21 is within a range that the rotor 1 can follow, and is set higher.

FIG. 3 shows a drive coil voltage waveform when an AC voltage is superimposed on a drive voltage only in a range where the aperture of the diaphragm is small, and a control signal 1 which is positional information of the diaphragm.
6, the OSC control circuit 13 turns on the AC oscillator 12 so that the AC voltage is superimposed only in the area on the small aperture side.
/ OFF control.

[0019]

As described above, the electric diaphragm device according to the present invention drives the input voltage of the diaphragm in the opening direction and the diaphragm in the closing direction on the input side of the signal amplifier circuit for driving the driving coil. An AC oscillator for applying an AC signal having an amplitude larger than the difference between the applied voltage and a control circuit for controlling the output of the AC oscillator, and applying an AC oscillator to the DC voltage applied to the drive coil. By superimposing the AC signal output from, the mechanical hysteresis that occurs when the aperture is opened and closed can be reduced, so the hysteresis of the voltage applied to the drive coil is reduced, and the control performance especially in the small aperture state is improved. Also, the speed of the opening / closing operation of the aperture can be set to be high.

[Brief description of the drawings]

FIG. 1 is a diagram showing an electromagnetic actuator control circuit of a diaphragm device according to the present invention.

FIG. 2 is a diagram showing a drive coil applied voltage waveform of the aperture device of the present invention.

FIG. 3 is a diagram showing a drive coil applied voltage waveform when the superposition of the AC voltage is turned on and off based on the position information of the diaphragm blades in the diaphragm device of the present invention.

FIG. 4 is a diagram showing a drive coil applied voltage waveform in a conventional diaphragm device.

FIG. 5 is an exploded perspective view of a part of a conventional diaphragm device.

FIG. 6 is a diagram showing an electromagnetic actuator control circuit of a conventional diaphragm device.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rotor 2 ... Brake coil 3 ... Drive coil 4 ... Hall element 5 ... Shaft 6 ... Drive lever 7 ... Aperture blade 8 ... Aperture blade 9 ... Operational amplifier 10, 11 ... Resistance 12 ... AC oscillator 13 ... AC oscillator control circuit 14 ... Low-pass filter 15 ... Luminance signal (light amount control signal) 16 ... Control signal (aperture position control signal) 18 ... Return spring 19 ... Drive coil applied voltage in opening direction operation 20 ... Drive coil applied voltage in closing direction operation 21 ... AC voltage superimposed waveform 22: hysteresis voltage 17: camera control circuit or exposure control circuit

Claims (2)

(57) [Claims] A rotor made of a permanent magnet having an N-pole region and an S-pole region formed on a surface thereof; a drive coil fixedly disposed to face the rotor surface with a predetermined gap; An electric diaphragm device including an electromagnetic actuator having a drive circuit for applying a drive voltage to a drive coil, wherein an input side of the drive circuit includes an applied voltage for driving the diaphragm in an opening direction. An AC oscillator that generates an AC signal whose amplitude is set to be larger than a difference between the applied voltage when the diaphragm is driven in the closing direction and a control circuit that controls an output of the AC oscillator is connected to the drive. An electric throttle device, wherein a voltage obtained by superimposing an AC signal output from the AC oscillator on a driving DC voltage is applied to the coil. 2. The electric diaphragm device according to claim 1, wherein the control circuit controls the AC oscillator to output an AC signal only when the diaphragm is in a small diaphragm region.