JPH0686592A - Electromagnetic driving apparatus - Google Patents

Abstract

PURPOSE:To improve reliability and accuracy of a position detecting signal of an electromagnetic driving apparatus by providing a means for cancelling noise due to excitation of coil which gives adverse effect on a magnetic sensor in such an apparatus for electromagnetically driving a control member to be controlled such as a light quantity control member or the like. CONSTITUTION:A driving current proportional to a coil excitation signal VS is inputted to a driving coil 24 through a buffer circuit 25 and when a rotor magnet 22 is excited, a member to be controlled is driven. In this case, a change of magnetic flux density of the rotor magnet 22 is detected by a Hall element 23 constituting a motor section 21 as a magnetic sensor 2 and its output is inputted to an adder circuit 27 through an amplifier 26. In this adder circuit 27, such a change of magnetic flux density is added to a coil excitation signal VS proportional to magnetic flux density due to excitation of coil outputted from the buffer circuit 25 in view of obtaining a position detecting signal VO from which noise element has been filtered. With this position detecting signal VO, the electromagnetic driving apparatus of a member to be controlled such as an aperture of a camera can be controlled.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electromagnetic drive device for controlling a member such as a light amount control member of a light amount control device as a controlled member and electromagnetically driving the controlled member.

[0002]

2. Description of the Related Art Conventionally, such an electromagnetic drive device has a drive coil as a drive source for driving a controlled member, and in order to obtain a feedback signal, how much the controlled device drives. Some have a position detecting means for detecting whether or not it has been hit. As the position detecting means, there is a magnetic generator and a magnetic sensor that senses the magnetism of the generator, so that the magnetism corresponding to the driven amount of the controlled member reaches the magnetic sensor from the magnetic generator. There is something I did. An example of an electromagnetic drive device having such a position detection means is shown in FIG. FIG. 5 is a diagram showing a cross section of a portion where the driving force generating portion and the position detecting means of the electromagnetic driving device including the yoke 31, the rotor magnet 32, the hall element 33, and the driving coils 34a and 34b are coupled.

In this device, for example, as shown in FIG. 3, the drive coil 4 (corresponding to 34a and 34b in FIG. 5) is energized in accordance with a coil excitation signal V _S , so that the rotor magnet 2 (32 in FIG. 5) is energized. Drive control). This rotor magnet is magnetized as shown in FIG. 5, and when it is rotated from the state shown in FIG. 5 by a certain angle, the magnetic flux density given to the Hall element 33, which is a magnetic sensor, changes, and the rotor magnet rotates by the magnetic flux density. The angle, that is, the amount of rotation can be detected. Since this Hall element 33 is represented by 3 in FIG. 3 and the other input V _DD given to this Hall element 3 is kept constant,
The output of the Hall element 3 represents the amount of rotation of the rotor magnet. The output of this Hall element 3 is the differential amplifier 6
The signal is amplified by and output as the position detection signal V ₀ .

[0004]

However, in such a prior art device, the energizing current of FIG. 3, that is, FIG.
The magnetic flux generated by the current flowing through the drive coils 34a and 34b shown by not only rotates the rotor magnet 32 but also jumps into the Hall element 33 (Hall element 3 in FIG. 3) to some extent. The effect of this, that is,
Not the original magnetic flux of the rotor magnet 32, but the magnetic flux from the drive coils 34a and 34b becomes unnecessary for the Hall element 33. For this reason, a signal appears as a noise component in the position detection signal V ₀ based on this unnecessary signal, which seriously adversely affects the position detection accuracy, and, in turn, this device and a system equipped with this device. There is a drawback that causes deterioration of reliability and malfunction.

The present invention seeks to overcome the above drawbacks by canceling or minimizing this noise.

[0006]

According to the present invention, a magnetic sensor, a means for canceling noise by excitation of a driving coil that affects the magnetic sensor, a typical example of which is a Hall element, or the noise is made extremely small. The problem is to be solved by providing means.

Specifically, for example, the size of a hole through which light is emitted, such as a diaphragm of a camera, can be adjusted, and a blade that is provided near the hole and shields the hole by an appropriate amount is controlled. The present invention relates to a member that is driven by the electromagnetic drive device of the present invention. This electromagnetic drive device is provided with a magnetic generator such as a permanent magnet and a magnetic sensor such as a Hall element that senses a magnetic amount that changes due to movement of the magnetic generator. The present invention relates to an electromagnetic drive device that also includes a drive coil for driving the. In such an electromagnetic drive device, a coil excitation signal for exciting the drive coil, in other words, means for feeding forward a compensation amount based on the magnitude of the current flowing in the drive coil to the output of the magnetic sensor is provided, or a Hall element is provided. In the case of using a magnetic sensor, it is possible to cancel or extremely reduce the above noise by providing a means for feeding forward the compensation amount to the reference input current to the Hall element.

[0008]

FIG. 4 is an exploded view of the structure of an example in which the controlled object is a member of the light quantity control device. The central part has the same structure as shown in FIG. 5, and the rotor magnet 32 drives and controls the blades 39 and 40 of the light quantity control device, and is magnetized into two poles in the radical direction. ing. The Hall element 3 is prepared to receive the magnetic flux of the rotor magnet 32 and detect the amount of rotation (rotational position) of the rotor magnet 32 from the amount of the magnetic flux. When the amount of rotation of the rotor magnet 32 is 0, the Hall element 33 is provided on the surface of the Hall element 33. It is arranged so that magnetic flux does not enter. The drive coil for rotating the rotor magnet 32 is divided into 34a and 34b and cooperates to give a rotational force to the rotor magnet. And, as shown in FIGS. 5 and 4, these are yokes 31 of ferromagnetic material.
The magnetic circuit is configured with and is structurally integrated.

This light quantity control device has a diaphragm base plate 37 for supporting each component, and also has an opening 41a together with a PCB substrate 35 and a meter cap 36, and blades 39, 4
A diaphragm case 41 for supporting 0 is attached, and further, a drive arm 38 for transmitting the drive force of the rotor magnet 32 to the blades 39, 40 is attached as shown in FIG. Then, the blades 39 and 40 have openings 39a and 40, respectively.
a, the opening 41a of the diaphragm case 41 and the diaphragm base plate 3
It can be regarded as a light quantity control member adapted to control the quantity of light passing through the opening 37a of the No. 7 opening. This feather 3
The magnets 9 and 40 are controlled by the rotor magnet 32 driven by the drive coils 34a and 34b via the drive arm 38 so that the light amount or the aperture value, which is a control amount, reaches a target value.

In the case of this embodiment, the controlled member is a member of the light quantity control device, but a circuit for giving an appropriate amount of movement to this member and electrically detecting the position of the controlled object which is this member, that is, aperture value information. An example of the above is shown in FIG. In the figure,
A drive coil for passing a drive current is indicated by 24, a rotor magnet is indicated by 22, and a controlled member coupled to the rotor magnet 22 is not indicated in the figure. The magnetic sensor that detects the magnetic flux density of the rotor magnet 22 and detects the moving position of the rotor magnet 22 constitutes the motor unit 21 with the Hall element 23. The drive coil 24 for rotating the rotor magnet 22 is energized by the buffer circuit 2 that amplifies the coil excitation signal V _S according to the coil excitation signal V _S.
It is designed to be performed through 5. The reference input current to the hall element 23 is performed by the constant voltage V _DD , and the output of the hall element 23 is input to the adder circuit 27 through the differential amplifier 26 which is an amplifier.

The differential amplifier 27, which is an adder circuit for receiving the output from this amplifier, is a circuit newly added in the present invention, and the output of the amplifier 26 which amplifies the output of the hall element 23 and the coil excitation signal V _S are obtained. This is an adder circuit for adding a proportional output from the buffer circuit 25 to cancel noise to generate a noise-free position detection signal V ₀ .

As described above, in the present embodiment having the configuration shown in FIG. 1, the coil excitation signal V _S passes through the buffer circuit 25 and the drive current proportional to V _S flows through the drive coil 24 to drive the rotor magnet 22. A controlled member (not shown) is controlled to detect a position which is a control amount as a rotation angle position of the rotor magnet 22, and the control amount is brought close to a target value. Since the rotor magnet 22 is magnetized like the rotor magnet 32 in FIG. 5, for example, when it rotates, the Hall element 23, which is a magnetic sensor, detects a change in the magnetic flux density of the rotor magnet 22 and sends it to the adding circuit 27 through the amplifier 26. Output. At this time, the magnetic flux density due to the excitation of the drive coil 24 is also detected by the Hall element 23, so that the addition circuit 2 is added as a noise component through the amplifier 26.
It is output to 7. Therefore, if the output to the adder circuit 27 is directly used as the position detection signal as in the conventional technique, the output naturally includes noise. Therefore, in this embodiment, the coil excitation signal V _S, which is proportional to the magnetic flux density due to the excitation of the coil, is output from the buffer circuit 25 to the adder circuit 27 and is added to or subtracted from the output of the amplifier 26 to cancel the noise component. The detection signal V ₀ is obtained.

In order to cancel this noise component, the resistance value of the adder circuit 27 must be set appropriately. I will describe how to determine it.

V _h is the Hall element output voltage V _DD which is the output of the amplifier 26, the reference drive voltage B _M for driving the Hall element is the magnetic flux density B _C at the Hall element position by the rotor magnet 22, and the drive coil 24 is the magnetic flux density B _C When the magnetic flux density I _C at the Hall element position is the drive current R _C flowing in the drive coil and the drive coil resistance is α and β are proportional constants, the following equation holds: V _h = α (B _M + B _C ) V _DD B _C = βI _C At this time, the relation between the resistance R ₃ and the resistance R ₂ of the adding circuit is shown.

[0015]

[Equation 1] And when the polarities of V _h and V _S are set to be inverted, the value of V _D in which the noise component due to the excitation of the drive coil is canceled can be obtained.

Since the value of R ₁ is not directly related to this cancellation, an appropriate value may be selected and defined. [Other Embodiments] FIG. 2 is a view showing another embodiment.
The motor unit is represented by 11, and its configuration is similar to that of the example of FIG. 1, and has a rotor magnet 12 for driving and controlling a controlled member (not shown) that is rotated by an electromagnetic force generated by the driving current of the driving coil 14. The Hall element 13, which is a magnetic sensor for detecting the magnetic flux density of the rotor magnet 12 to detect the rotation angle position of the rotor magnet, and thus the position of the controlled member, is provided. Then, a drive current is supplied to the drive coil 14 via the buffer circuit 15 that amplifies the coil excitation signal V _S. The output of the hall element 13 is amplified by the amplifier 16 and output as the position detection signal V ₀ .

In the case of this embodiment, an adder circuit 17 is provided to add the output of the buffer circuit 15 proportional to the coil excitation signal V _S and the constant voltage −V _DD, and the adder circuit 17 adds noise to the hall element 13. It is designed to generate a driving voltage for cancellation.

With this configuration, the coil excitation signal V_S The
V through the buffer circuit 15 _S Drive voltage proportional to
Current is applied to the drive coil 14, which causes the rotor magnet
The net 12 is driven to control a controlled member (not shown),
Bring the amount closer to the target value. Rotor magnet 12 rotates
When driven, the Hall element 13, which is a magnetic sensor, goes low.
Detects changes in the magnetic flux density of the tamagnet and outputs the detection
Position detection signal V through amplifier 16₀ Output as
It At this time, according to the conventional technique, the current is applied to the drive coil 14.
The density due to the drive current is also detected by the Hall element 13.
The position detection signal V is passed through the amplifier 16.₀ To noise
Will be output as. But this implementation
In the case of the example, it is proportional to the magnetic flux density due to the excitation of the drive coil.
Signal to coil excitation signal V_S Buffer circuit 15 passing signal
It is made from the signal No. and is added to the Hall element drive voltage through the adder circuit 17.
If added, it corresponds to Hall output due to excitation of the drive coil.
Hall element drive voltage corrected by
The output of the child can be adjusted, resulting in a drive current
Featuring a proportional signal to the Hall element drive voltage
Cancels noise due to drive current
It becomes possible to do. However, in the case of this embodiment, it is modified
Hall element drive voltage and magnetic flux density of rotor magnet
Depending on the frequency, new noise is generated, but the amount is extremely small.
So the cancellation above can be virtually achieved
It

[0019]

As described above, by providing the means for canceling or substantially canceling the noise due to the excitation of the coil which influences the magnetic sensor, the position detection signal of the electromagnetic drive device using the magnetic sensor is increased. reliability·
Not only can high accuracy be improved, but high performance and high reliability of this device and a system equipped with this device can also be realized.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of an embodiment implementing the present invention.

FIG. 2 is a circuit configuration diagram of another embodiment implementing the present invention.

FIG. 3 is a conventional circuit configuration diagram.

FIG. 4 is a partial disassembling component in which the controlled device is a light amount control device.

FIG. 5 is a sectional view of a central portion of an electromagnetic drive unit.

[Explanation of symbols]

1, 11, 21 motor unit 2,12,22,32 rotor magnet 3,13,23,33 Hall element 4,14,24,34a a magnetic sensor, 34b drive coils 17, 27 adder circuit V _S coil excitation signal V ₀ position detection signal

Claims (4)

[Claims] 1. A driven member for driving a controlled member, comprising: a magnetic generator and a magnetic sensor for sensing a magnetic amount of the magnetic generator; and a drive coil for driving the magnetic generator. In the electromagnetic drive device, by providing means for feeding forward the compensation amount based on the coil excitation signal for exciting the drive coil to the output of the magnetic sensor, the noise given by the magnetic force of the drive coil to the magnetic sensor is canceled. An electromagnetic drive device characterized by: 2. The electromagnetic drive device according to claim 1, wherein the magnetic sensor is a Hall element. 3. The magnetic sensor is a Hall element, and means for feeding forward a compensation amount based on a coil excitation signal for exciting a drive coil to a reference input current to the Hall element is provided. The electromagnetic drive device according to claim 1. 4. The electromagnetic drive device according to claim 1, wherein the controlled member is a member of a light amount control device.