JP3435907B2 - Camera electric hoist - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electric film winding apparatus for a camera which winds a film electrically. 2. Description of the Related Art FIG. 1 shows a conventional camera 1 in which electric driving of a camera mechanism such as a shutter and electric driving of film winding are performed by separate motors. A motor 2 drives a shutter 3 and the like via a speed reduction mechanism (not shown). The motor 4 drives the film take-up spool 5 via a speed reduction mechanism (not shown). 6 is a patrone and 10 is a film drawn from the patrone 6. As the film 10 is wound on the spool 5, the winding diameter of the spool 5 changes, and the winding diameter of the film increases from the initial diameter 11a to the diameter 11b. Since the film withdrawing force F from the patrone 6 is almost constant, the film winding torque (= radius of film winding diameter R ×
F) increases according to the number of winding frames. If the gear ratio K of the film winding mechanism is constant, the load torque T (= C × R × F / K, C is a coefficient) to the motor 4 increases. FIG. 2 shows the characteristics of the motor 4. The horizontal axis is the load torque T, and the vertical axis is the output P of the motor. Assuming that the load torque at the start of film winding is T1 (output P1), the load torque at the end of the film is T2 (output P2), and the output increases. The film winding time t is a value (= W / P) obtained by dividing the film winding work W (= F × length of one frame of film) by the output P (= W / P). Since the output P increases as described above, the winding time becomes shorter as the film winding advances. FIG. 3 shows the current I1 of the motor 2 for driving the shutter and the like and the current I2 of the motor 4 for driving the film winding. The motor 4 is started after a predetermined time t3 has elapsed from the start of the motor 2. This is to prevent the load on the power supply from increasing due to the overlap of the rush currents of the two. The drive time t 1 of the motor 2 is not significantly affected by the number of film windings. The film winding time t2 per unit length varies from the time t2,1 at the start of film winding to the time t2,2 at the end as described above. In order to shorten the photographing interval, it is desired that both are completed at substantially the same timing, so that the gear ratio must be set so as to be as shown in FIG. [0008] In this case, at the end of the film, the winding of the film is completed earlier, and the driving of the shutter or the like is awaited, so that time is wasted. If there is enough time for the hoisting, it is preferable to shift the timing of the rush current as much as possible from the viewpoint of load on the power supply. Alternatively, in order to secure the film stopping accuracy, it is preferable to drive the film as long as possible. SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems, and reduces a load applied to a power supply by a motor.
The purpose is to ensure film stop accuracy. In order to achieve this object, a first invention is a film winding mechanism (5) for winding a photographic film, and a first motor (4) serving as a driving source of the film winding mechanism. ), A camera mechanism (3) constituting a movable portion of the camera other than the film winding mechanism, a second motor (2) serving as a driving source of the camera mechanism, and a first motor after a set time from the start of the second motor. And a counting means (23) for counting the number of frames of the photographic film and outputting a signal corresponding to the number of shot frames, wherein the timer device responds to the output of the counting means. Thus, the setting time is changed. In the above-described electric motor winder for a camera, the timing of starting the rush current is shifted as much as possible by changing the start timing of the film wind motor in accordance with the number of winding frames. Thus, the load on the power supply can be reduced. Further, by changing the driving speed of the film winding motor according to the number of winding frames, the film winding motor can be driven at a low speed as much as possible, and the film stopping accuracy can be secured. Embodiments of the present invention will be described below with reference to the drawings. FIG. 5 is a block diagram showing an embodiment of an electric hoist for a camera according to the present invention. In FIG. 5, a control section 21 controls the entire apparatus. The power supply 22 is a power source for the entire apparatus, and power is supplied to the motors 2 and 4 via motor control units 25 and 26, respectively. The frame number counting unit 23
The number of winding frames of the film 10 is counted optically or mechanically, and a signal corresponding to the number of shooting frames is output to the control unit 21. The film moving amount detecting unit 24 detects the moving amount of the film and outputs a signal corresponding to the winding amount for one frame to the control unit 21. The motor control unit 25 controls driving of the motor 2. The motor control unit 26 controls driving of the motor 4. The control unit 21 changes the time difference between the activation of the motor 2 and the motor 4 based on a signal corresponding to the number of frames to be shot supplied from the frame number counting unit 23. That is, FIG.
As shown in (a), as the number of frames increases from N1 to N3, the control unit 21 increases the delay time from t3,1 to t3.
Control is performed so that the operation of the motor 4 is completed almost simultaneously with the completion of the operation of the motor 2. When the film winding amount reaches a predetermined value based on a signal corresponding to the winding amount for one frame supplied from the film moving amount detecting unit 24, the motor 4 is driven. The mode is changed from the full drive duty to a mode in which the speed is reduced by the PWM control. That is, as shown in FIG. 4B, as the number of frames increases from N1 to N3, the control unit 21 changes the duty of the PWM control from D1 to D3 to reduce the speed. Thereby, the control unit 21
Control is performed to ensure film stop accuracy. In this embodiment, the case where the frame number counting section 23 and the film moving amount detecting section 24 are provided independently has been described. However, the film moving amount detecting section 24 may be shared by the frame number counting section 23. it can. In the embodiment, the drive duty is changed as a method of changing the drive speed. However, the motor drive speed may be changed by changing the drive voltage or the drive current. As described above, according to the camera electric winder of the present invention, the timing of starting the film winding motor is changed according to the number of winding frames, so that an inrush current flows. The timing can be shifted as much as possible to reduce the load on the power supply. Further, by changing the drive duty of the film winding motor in accordance with the number of winding frames, the film winding motor can be driven at a low speed as much as possible to ensure film stop accuracy.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a cross-sectional view illustrating an example of a conventional electric hoist of a camera according to the present invention. FIG. 2 is a characteristic diagram showing an example of a conventional electric hoist for a camera according to the present invention. FIG. 3 is a characteristic diagram showing an example of a conventional electric hoist for a camera. FIG. 4 is a characteristic diagram showing an example of an electric hoisting device for a camera according to the present invention. FIG. 5 is a block connection diagram showing an example of a camera electric hoist according to the present invention. [Description of Signs] 1 Camera 2 Motor 3 Shutter 4 Motor 5 Spool 6 Patrone 10 Film 21 Control unit 22 Power supply 23 Frame number counting unit 24 Film movement detection unit 25 Motor control unit 26 Motor control unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G03B 17/00 G03B 17/26-17/34 G03B 17/38-17/46

Claims (1)

(57) [Claim 1] A film winding mechanism for winding a photographic film, a first motor serving as a drive source of the film winding mechanism, and a movable portion of a camera other than the film winding mechanism. A camera mechanism; a second motor serving as a drive source of the camera mechanism; a timer device for activating the first motor after a set time from the activation of the second motor; Counting means for outputting a signal corresponding to the number of completed frames, wherein the timer device changes the set time according to the output of the counting means.