JPS6320509A - Position detector - Google Patents

Abstract

PURPOSE:To eliminate the need for wiring, etc., such as a signal line from an initial position and to eliminate a mechanical contact, etc., by detecting counter electromotive force generated when a body conveyed by being driven by a stepping motor abuts on a stopper to reverse, and detecting the arrival of the driven body at a specific position. CONSTITUTION:The upward raised part 26 of a stop ring 25 is pressed against an initial stopper 29 and inhibited from further rotating as shown by an arrow. Then, the upward raised part t is held in the pressed state at the position of the initial stopper 29 even through the excitation of phases 9-11 because the stopper position is closer. In the excitation state of a phase 12, the motor is caused to reverse at positions (c) and (k) as stable points of B-phase excitation because a position (c) is closer, so that counter electromotive force is generated in a phase A as a nonexcitation phase. This counter electromotive force is detected by a counter electromotive force detecting circuit 5 and recognized by a control part to detect the stepping motor reaching the initial position.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a position detection device for a driven body moved by a stepping motor.

[Prior art and its problems] Conventionally, in a positioning device using a stepping motor, in order to detect the initial position, a photo sensor is provided at the initial position, and a protruding piece or the like is provided on the driven body to block the optical path of the photo sensor. The protruding piece blocks the optical path of the photosensor, thereby detecting the initial position sb of the driven body. However, a photo sensor requires a driving signal line and a detection signal line, and it is troublesome to wire these signal lines. Further, there is a drawback that detection errors occur when dust or the like adheres to the photo sensor.

In addition, there was a device that replaced the photo sensor with a micro switch at the initial position and detected the initial position by turning on/off the micro switch, but wiring the signal line from the micro switch was also avoided. I couldn't. Additionally, the fibroswitch has mechanical contacts, which poses a problem in reliability.

[Object of the invention] The present invention has been made in view of the problems of the prior art described above.
Eliminates the need for wiring signal lines from the initial position.
Another object of the present invention is to provide a highly reliable position detection device that does not have mechanical contacts or the like.

[Summary of the Invention] As a means for achieving the above-mentioned object, a stopper is provided at a positioning location of a driven body driven by a stepping motor to prevent further movement of the driven body;
a driving means for supplying electric power to each excitation phase of the stepping motor to rotate the motor; a first detection means for detecting a specific time after a drive signal of a predetermined excitation phase by the driving means is turned off; and a second detection means for detecting a back electromotive force generated in the predetermined excitation phase within the detection time of the detection means, the second detection means being transferred by rotation of a stepping motor driven by a drive means. The arrival of the driven body at a predetermined position is detected by detecting the back electromotive force generated when the driven body contacts the stopper and then reverses to a stable position determined by the exciting phase of the stepping motor.

[Example 1] Hereinafter, an example according to the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of a motor control circuit section according to an embodiment of the present invention. In the figure, 1 is a control section that performs drive control of a stepping motor 4, and 2 is a control section that drives the stepping motor 4 under the control of the control section 1. 3 is a phase excitation control circuit that controls the excitation phase of the stepping motor 4 and outputs phase excitation signals A, λ, B, r3 of the stepping motor 4; 5 is a phase excitation control circuit that controls the excitation phase of the stepping motor 4; This is a back electromotive force detection circuit that detects the back electromotive force generated in the phase, and in this embodiment, the back electromotive force of the A phase can be detected.

The stepping motor 4 is a PM type motor that rotates 18 degrees per step, and its rotation is controlled by 1-2 phase excitation.

Details of the back electromotive force detection circuit 5 are shown in FIG.

In FIG. 2, 3 indicates a driver circuit portion of the stepping motor 4 of the phase excitation control circuit shown in FIG. 1, and 4 is the stepping motor. 11 is an edge detection unit A that detects the negative edge of the A-phase drive signal from the phase excitation control circuit 3; 13 is an edge detection unit B that detects the negative edge of the B-phase drive signal from the phase excitation control circuit 3; 115 is an edge detection unit A gate pulse generator 17 is set by the A-phase detection signal 12 from the edge detector B13 and reset by the B-phase detection signal 14 from the edge detector B13. This is a gate section that detects the back electromotive force pulse generated in the

When driving the stepping motor 4, the drive signal A
Inductive impulses may occur when switching between phase and A phase, and between B phase and 100 phase.

An example of the generation of this induced impulse is shown in FIG.

501J (induction impulse) shown in the figure.As shown in Figure 3, the induction impulse generated in the A phase is at the falling edge of the A phase, and is far from the generation timing of the back electromotive force to be detected that occurs in the A phase. The gate signal 16 of the back electromotive force detection circuit 5 removes the distortion of this induced impulse.

The gate signal 16 is the A phase detection signal 12 and the B phase detection signal 14.
If a back electromotive force I is generated during that time, a back electromotive force detection signal 18 is output as shown in the figure.

In addition, the gate part 17 is connected to the A phase and B phase when switching between phase input and 100 phase.
In order to also eliminate the influence of the induced impulse induced in the phase, the gate signal 16 and the B phase signal are further ANDed,
By the AND of this and the counter electromotive force detection signal 18, it is determined that the desired initial position has been reached.

FIG. 4 shows an example in which the stepping motor driven by the above configuration is applied to aperture control of a camera.

In FIG. 4, 6 is a drive shaft of the stepping motor 4, and a gear 7 is pivotally supported on the drive shaft 6. Reference numeral 20 denotes an automatic diaphragm mechanism of the camera, and a drive ring 21 is rotatably disposed at the outermost periphery of the automatic diaphragm mechanism 20 and includes an outer periphery gear portion 23 that is constantly engaged with the gear 7 on a part of the outer periphery. and rotates according to the rotation of the stepping motor 4. This drive ring 21 is provided with a protruding piece 22 that protrudes from the inner circumference, and the protruding piece 22 is apertured by the elastic force of a spring 28 that presses the aperture ring 25, which opens and closes the aperture blades 31, in the direction of arrow B. Upper rising portion 2 at the tip of the protruding portion 25a of the ring 25
6, and rotates the aperture ring 25 in accordance with the rotation of the drive ring 21. The rotation of the drive ring 21 and the aperture ring 25 is regulated by an initial stopper 29 disposed on the base 35 at an initial position in an open aperture state and an aperture position stopper 30 disposed in a position in a narrowed state.

Further, aperture blades 31 are rotatably attached to pins 32 implanted in the base 35, and the aperture blades 31
An aperture blade drive pin 27 embedded in the aperture ring 25 is inserted into a long hole 33 provided in the aperture blade 3 .
1, the aperture is opened by rotating the aperture ring 25 in the direction of arrow A, and is brought into a narrowed state by rotating in the direction of arrow B. One end of a spring 28 that presses the aperture ring 25 in the direction of arrow B is engaged with the aperture ring 25, and the other end of the spring 28 is engaged with the base 35.

When power is not supplied to the stepping motor 4, the automatic diaphragm mechanism 20 uses the spring 28 according to this embodiment, depending on the balance between the spring force of the spring 28 and the so-called detent stop torque when the stepping motor is not energized. Since the main function is to remove play in the mechanical transmission mechanism, its spring force is small, and the position of the aperture ring 25 is determined by the balance between the spring force and the detent stop torque, and this position is arbitrary. When the release switch or the like of the camera is pressed to start the release, the control section 1 first controls the drive circuit 2 to fully open the aperture. To fully open the aperture, the stepping motor 4 is rotated in the reverse direction, and the drive ring 21 is moved in the direction of the arrow in FIG.
This is done by rotating it until it touches 9. Details of this fully open aperture position detection will be described later.

Then, a photometry section (not shown) performs photometry and sends photometry information to the control section 1. Upon receiving the photometry information, the control unit 1 rotates the stepping motor 4 forward by an amount corresponding to the photometry result from the aperture fully open (initial position) position, and controls the aperture mechanism 20.
The drive ring 21 is rotated in the direction of arrow B to obtain an appropriate aperture. Then, the shutter is operated to expose the film and the photographing is completed. Then, in preparation for the next photograph, the stepping motor 4 is reversed again, and the aperture ring 25
Rotate until it contacts the initial stopper 29.

Here, the process of detecting contact with the initial stopper 29 will be described below with reference to the timing chart of FIG. 5(A).

The stopping position of the rotor magnet in this case is shown in Figure 5 (B).
The relationship is as shown in FIG. 2, and will be explained using an example in which the C position is set to the initial position.

In this case, the initial stopper 29 position can be set between the f position and the g position, or between the g position and the h position depending on the relationship between the spring force of the spring 28 and the motor torque.

Then, each excitation phase of the stepping motor 4 is sequentially excited as shown in FIG. 5(A). In this case, the excitation provides a reverse drive signal for rotation in the direction of arrow A in FIG. 4. The motor is driven in phases 1 to 7, and the stable position of the rotor of the motor 4 is set to the f position. Further, when phase 8 is reached, the upper rising portion 26 of the aperture ring 25 comes into pressure contact with the initial stopper 29, and subsequent rotation in the direction indicated by the arrow is prevented. Thereafter, even with the excitation in phases 9 to 11, since the stable point is closer to the stopper position, the state of pressure contact with the initial stopper 29 position is maintained. Furthermore, by setting the wJ magnetic state shown in phase 12, since the C position is closer to the stable point in B-phase excitation, the motor reverses, and the A-phase, which is the non-excited phase. A back electromotive force is generated. This back electromotive force is detected by the back electromotive force detection circuit 5.
, the controller 1 recognizes that the stepping motor 4 has reached the initial position.

After detecting that the initial position has been reached, the control unit 1 applies a holding voltage to the stepping motor 4 to maintain the initial position via the drive circuit 2 and the phase excitation control circuit 3, thereby ensuring that the initial position is maintained. , and waits for the start of forward rotation.

Thereafter, the control section 1 performs photometry as described above, instructs the drive circuit 2 to rotate the stepping motor 4 in the normal direction, and simply provides a predetermined amount of clock pulses to the phase excitation control circuit 3 based on the photometry results, and the stepping motor 4 in the forward rotation direction by a clock pulse amount from the initial position, and the aperture ring 25 is rotated in the direction of arrow B to obtain an appropriate aperture. Then, take a picture with the appropriate aperture.

If the back electromotive force detection circuit 5 can detect not only the back electromotive force generated in the A phase but also the back electromotive force generated in other phases,
The position and initial position of the initial stopper 29 can be set more freely.

Further, this embodiment can be applied not only to an aperture mechanism of a camera but also to mechanisms using various stepping motors. For example, the present invention is used in a floppy disk drive device for an electronic still camera, and can also be applied to a magnetic rad seek mechanism in a 2-inch magnetic disk device for recording imaged data.

[Effects of the Invention] As explained above, according to the present invention, there is no need to use a photo sensor or a microswitch to detect a predetermined position, there is no need to route unnecessary signal lines, and the configuration is simple and highly reliable. A position detection device with high performance can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a stepping motor control section according to an embodiment of the present invention, FIG. 2 is a detailed circuit diagram of a back electromotive force detection circuit of the stepping motor control section shown in FIG. 1, and FIG. Drive signal A phase, A phase, B
Figure 4 shows an example of the generation of induced impulses when switching between phase and 100 phases. Figure 4 is a diagram showing the application of the stepping motor control section shown in Figure 1 to the diaphragm mechanism of a camera. Figure 5 (A) is Predetermined position detection timing chart in 1-2 phase excitation of this embodiment. FIG. 5(B) is a PM type joke development diagram showing the stop position of the rotor magnet in 1-2 phase excitation of this embodiment. In the figure, 1... control unit, 2... drive circuit, 3... phase excitation control circuit, 4... stepping motor, 5...
Back electromotive force detection circuit, 6... Stepping motor drive shaft, 7... Gear, 11.13... Edge detection section, 15
... Gate pulse generating section, 17... Gate section, 21
... Drive culling, 22... Protruding piece, 23... Outer periphery gear part, 25... Aperture ring, 26... Upper rising part, 28... Spring, 29... Initial stopper, 3
1... Aperture blade, 41... Back electromotive force pulse, 50.
...It is an inductive impulse. Patent Applicant: Kobaru Co., Ltd. (Figure 1, Figure 3, Figure 5 Old) Figure 5 (A)

Claims (2)

[Claims] (1) A position detection device for a driven body moved by a stepping motor, which includes a stopper disposed at a positioning location of the driven body to prevent further movement of the driven body, and a stopper for preventing further movement of the driven body; a driving means for supplying power to each excitation phase to rotate the motor; a first detection means for detecting a specific time after the drive signal of a predetermined excitation phase by the driving means is turned off; and the first detection means a second detection means for detecting a back electromotive force generated in the predetermined excitation phase within a detection time of , the second detection means being transferred by rotation of a stepping motor driven by the drive means. The arrival of the driven body at a predetermined position is detected by detecting a back electromotive force generated when the driven body contacts the stopper and then reverses to a stable position determined by the excited phase of the stepping motor. A position detection device characterized by: (2) A patent claim characterized in that the first detection means detects between an edge portion where a predetermined excitation phase drive signal is OFF and an edge portion where a drive signal of another excited phase is partially superimposed and OFF. The position detection device according to item 1.