JPS589219Y2 - Overload detection device for electric hoisting device - Google Patents

Description

[Detailed Description of the Invention] The invention is to detect the overload applied to the motor of the electric winding device for the camera by electrical means when winding of the film is completed and at the end of the film. Even if the load on the motor fluctuates due to temperature changes, film type, etc., the completion of winding and the end of the film can always be detected in the optimal condition, and overload on the film winding member and camera can be detected. Regarding an overload detection device for an electric hoisting device to minimize the

2. Description of the Related Art Conventionally, motorized camera playback devices have been known that use a mechanical latch or a timer as a means for detecting the completion of film playback and the end of film playback.

In such a detection means 1, when the photographing operation is completed, a signal for commanding film winding is sent from the camera body side to the electric winding device, and this signal starts the motor to start the film winding device. Carry out hoisting.

When the film is finished being played, the motor is overloaded, so the clutch is activated to control the opening and closing of an overload switch, etc., and cut off the power to the motor.

Furthermore, since the latch means alone can detect the completion of film winding but cannot detect the end of the film, a timer separate from the clutch means is used to detect the end of the film.

If the time required for normal film winding is, for example, 0.5 seconds, this timer should be set in advance so as to output an output signal in about 0.7 seconds. At the same time, start a timer, and as soon as the film has finished playing (reset this timer once). During normal winding, for example, 0.5 seconds have passed from the start of film winding, the film will start winding. is completed,
At the same time, the timer is running, so no timer output is output.

However, when the film ends, the timer starts simultaneously with the start of film winding, but since the film stops midway, no reset signal is generated, and the timer is not reset even after 0.5 seconds have elapsed.

Therefore, the timer continues to operate and generates an output signal after a preset period of time (e.g., fc_O, 7 seconds as described above) has elapsed.

This output signal detects that the film has finished,
For example, the display device may be activated to indicate that the photographer has finished shooting the film.

However, in such conventional devices, even if the load on the motor fluctuates widely due to temperature changes, film type, etc., the detection level at the completion of film winding or the end of the film remains unchanged. Because this was constant, there were many drawbacks, such as an abnormal overload being applied to the hoisting member of the electric hoisting device and the camera body.

The idea was to improve these conventional drawbacks by automatically adjusting the detection level at the end of the film or when the film has finished, even if the temperature changes, the type of film (and therefore the load on the motor) fluctuates. By controlling the winding mechanism so that it can always operate in the optimal condition, it minimizes the overload of the winding member and camera body, and reduces the overload of the motorized drive unit, which has been designed to be able to handle a wide range of usage conditions. A detection device is provided.

Hereinafter, an unconceived embodiment will be explained with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of the invention, where E is a power source, So is a power switch, 1 is a motor switching circuit, M is a film winding motor, and 2 is a torque Et flow level of the motor M. Load current level detection circuit to detect,
3 is a timer, 4 is a gate circuit, 5 is a memory circuit, 6 is an overload level setting circuit, 1 is a comparison detection circuit, and 8 is a protection safety circuit.

Next, the operation of fC1 in FIG. 1 will be explained.

Power switch S.

FI: With FI turned on, the release button is pressed on the camera body to take a picture, and when the shutter curtain finishes running, the film is rolled from the camera body. A signal is issued to command the top.

When this signal is output, the motor switching circuit 1 enters the on state and maintains the on state even if the signal instructing the film to play is removed.

Therefore, the motor M is energized and started, and starts playing one film.

When the motor M is started, the torque of the motor M is detected as a load current level by the load current level detection circuit 2f, and its output signal is input to the gate circuit 4.

However, since the gate circuit 4 is off during the initial period of energization to the motor M, the output of the load current level detection circuit 2 cannot pass through the gate circuit 4, and the voltage is applied to the memory circuit 5 and the protection safety circuit 8. Not done.

On the other hand, when the motor switching circuit 1 is turned on, voltage is applied to the timer 3, so the timer 3 starts operating.

After a certain period of time, when the time set in the timer 3 has elapsed, the timer 3 outputs an output and turns the gate circuit 4 into an on state.

Therefore, the output of the load current level detection circuit 2 is input to the storage circuit 5, the protection safety circuit 8, and the comparison detection circuit 7, and the output signal of the load current level detection circuit 2 during winding is stored in the storage circuit 5. be done.

The signal stored in the storage circuit 5f is input to an overload level setting circuit 6f and converted, and the comparison detection circuit 7f sets an overload level value.

This set overload level value is compared by the comparison detection circuit 7 with the output signal of the load current level detection circuit 2 while the motor M is energized.

Then, when the output signal of the load current level detection circuit 2 exceeds a set overload level value, the comparison detection circuit T outputs an output signal, turns off the motor switching circuit 1, and stops energizing the motor M.

In addition to the above operation, in the protection safety circuit 8, the timer 3 outputs an output, and the gate circuit 4 turns on (from the moment it turns on,
The output signal of the load current level detection circuit 2 is continuously compared with a preset reference value, and when the output signal of the load current level detection circuit 2 exceeds the reference value, an output is output and the motor switching circuit 1 is turned off. However, this protective safety circuit 8 has the above reference value set so that it operates in reverse around the maximum rated current value of the motor M, and for example,
When the film ends while the timer is running, or in the case of an abnormal accident, the above overload level setting value is set to an abnormal value, the comparison detection circuit does not output an output signal, and the motor rotation stops. If the motor M continues to be energized despite the It is something to do.

The above action has been explained briefly, but the action will be explained in more detail.

FIG. 2 illustrates the state in which the current flowing through one motor changes with the passage of time after energization of the motor starts, and shows the state in which the current flowing through one motor changes as time passes.

When the motor starts to be energized and starts at , a large starting current flows in the initial state (here, a large starting current flows, and at time t1f, it becomes a steady current).

Then, at time t2f, the winding of the film is completed and the motor suddenly becomes overloaded, and at time t3 the motor current reaches several times the steady current shown between times t0 and t2.

In addition, temperature changes, film types, etc. (Thus, the motor current changes as shown in the figure, for example, A, C, C).

As can be seen from this figure, at time t.

If the starting current that flows between t and tl is input to the memory circuit 5 or the protection and safety circuit 8f, normal operation will not be possible. Therefore, as mentioned above, the f timer 3 is provided, and the set value of this timer 3 is set to an appropriate value longer than t0 time. Set the time to time t1
Output the output of timer 3 at an appropriate time between t2 and t2,
The motor current value between times t1 and t2, that is, the steady current value of the motor during film winding, is stored in the memory circuit 5f and is input to the protective safety circuit 8.

Therefore, in the overload level setting circuit 6,
The above-mentioned steady current value stored in the memory circuit 5i is multiplied by n (
n>1)' is converted and input as an overload level value to the comparison detection circuit 7t.

In this way, even if the motor current changes as shown in the curves A, 8 and 8 in Figure 2 due to temperature changes, for example, the comparison will always be made with the changed steady current value as the standard. Detection is performed.

Then, when the film has finished playing at time t3f, the output of the load current level detection circuit 2 exceeds the overload level value set by the comparison detection circuit 7f.
The comparison detection circuit 7 outputs an output, which turns off the motor switching circuit 1 and stops energizing the motor.

Next, a concrete example shown in FIG. 3 will be explained.

First, to explain it in correspondence with the block diagram shown in FIG. 1, the motor switching circuit 1 includes a transistor TR.
2, a transistor TR1 for self-holding this transistor TR2, etc., the load current level detection circuit 2 consists of a resistor R6, and the timer 3 consists of a resistor R2.
1, a time constant circuit consisting of capacitor C3, and resistor R25
and a bias circuit consisting of R24, and a programmable
It is composed of a unijunction transistor PUT.

The gate circuit 4 includes a three-terminal thyristor SCR and a relay RL,
and contacts RL1 and RL2 of relay RL.

Furthermore, the memory circuit 5 is composed of an operational amplifier 0PA1, a resistor R2, and a capacitor C1, the overload level setting circuit 6 is composed of an operational amplifier 0PA2 and resistors R3 and R4f, and the comparison detection circuit 1 is composed of an operational amplifier 0PA3 and resistors R3 to R8f. be done.

Furthermore, the protective safety circuit 8 is composed of an operational amplifier 0PA4, resistors R17 and R18, a transistor TR3, and the like.

Note that S is a winding command switch that is temporarily turned on in order to command film winding when the photographing operation is completed on the camera body side 1, and then immediately turned off.

Further, ZD is a zener diode for obtaining a constant voltage, Co is a capacitor for smoothing the terminal voltage of the resistor R8, and OPA and OPAC) are power supplies for operating the operational amplifier.

Next, the function of the power switch S will be explained.

When the hoisting command switch S is temporarily turned on while the power source E such as a battery is applied to the circuit, the transistor TR2 is turned on.

Therefore, current flows through the motor Mf through the resistor R6, and the motor M starts.

At this time, the input side of the operational amplifier 0PA4 is connected to the contact RL2f of the relay RL, so the voltage is O volts, and the input side is connected to the zener voltage of the zener diode ZD through the resistor R15.
Since a positive voltage divided by and R16 is applied, a negative voltage is generated at the output side of the operational amplifier OPA.

Therefore, transistor TR3 is turned off.

On the other hand, as a current flows through the resistor R8, a voltage is generated, the contact RL1 is closed during the timer operation, and the operational amplifier 7'0PA1 generates a negative output.

Therefore, since this signal is applied to one input terminal of the operational amplifier oPA2, the operational amplifier OPA2 generates a positive output, and a positive voltage is input to the input side of the operational amplifier OPA3.

Further, since an O volt potential is applied to one input terminal of the operational amplifier 0PA3 via the contact RL2 of the relay RL, a positive voltage is generated on the output side of the operational amplifier 0PA3.

Therefore, transistor TR is turned on.

Therefore, even if the hoisting command switch S is temporarily turned on and then turned off, the transistors TR1゜TR2
f thus constitutes a self-holding circuit, and transistor TR2
remains on.

Simultaneously with this operation, when the transistor TR2 turns on, current flows through the time constant circuit consisting of the resistor R21 and the capacitor C3, starting a timed operation.

After a certain period of time, when the capacitor C3 is charged to a predetermined value, the programmable unijunction transistor PUT turns on, turning on the three-terminal thyristor SCR.

As a result, relay RL is energized, and its contact RL1
When the resistor R8 is opened, the contact RL2 is switched and connected from the ground side to the non-ground side of the resistor R8.

As a result of this operation f, the voltage generated by the resistor R8f is cut off and stored in one input terminal of the operational amplifier 0PA1, and is applied to the input terminal of the operational amplifier 0PA4 and one input terminal of the operational amplifier 0PA3, respectively.

This state is a state in which the motor current during winding of the film after t1 time or more in FIG. 2 is a steady load current.

Now, the voltage at point a in Fig. 3 is Va, and the voltage at point b is V.
Assuming that the voltage at points b and c is Vc, Va is applied to one input terminal of the operational amplifier 0PA1, and is integrated by the integrating circuit 1 consisting of the operational amplifier OP A1 and the capacitor C1.
The capacitor C1f stores a voltage proportional to Va immediately before the contact RL1 opens.

Therefore, the voltage vb at point b is Vb = -K Va
(V] (K is a positive constant), and this voltage vb
is applied to one input terminal of the operational amplifier 0PA2.

Furthermore, Vb is inverted and once amplified by the operational amplifier 0PA2, and a voltage R3 of Vc - vbCV is generated at point C.

At this time, resistor R3s R4 so that R4/R3>1
If we choose the value of and set K>1, then Vc---””・Vb
=(-current) ・(-KVa)K-”' ・V”a=nV
a(V) (where n = -”')3R3.

That is, the voltage Vc at point C is n times the voltage Va at point a (n>
1) A voltage of the same polarity is generated, and this voltage at point C is divided by resistors R6 and R6, and is input as an overload level setting value to the input side f of the operational amplifier 0PA3.

On the other hand, since the voltage at point a is applied to one input terminal of the operational amplifier 0PA3 via the relay contact RL2, the operational amplifier 0PA3 continuously compares it with the above-mentioned overload level setting value during winding.

Furthermore, a voltage obtained by dividing the zener voltage of the zener diode ZD by resistors R15 and R16, that is, a voltage Vd at point d, is applied to one input terminal f of the operational amplifier OPA4. Here, since the voltage Va at point a is applied, va and Vd are always at the operational amplifier 0P.
A-Thus, the comparison continues throughout the winding.

Then, if the voltage Vd at point d is selected to be an appropriate value f that is almost equal to Va when a current equivalent to the maximum rated current of the motor M flows through the motor M, then from time t1 to time t2 in FIG. During the period f, the voltage at point f is a negative voltage, and the transistor TR3 maintains the off state.

Moreover, between time t1 and t2 in FIG. 2, since the voltage at one input terminal of the operational amplifier 0PA3 is selected to be lower than the voltage at the tenth input side, the 0 point (this is a positive A voltage is generated and the transistor TR1 continues to be in the on state.

Next, at time 13F in FIG. 2, when the film has finished playing, the motor Mf is overloaded.
Therefore, an overcurrent flows through the motor M.

Therefore, an overcurrent also flows through the resistor R8, and the voltage Va at point a
to rise.

Therefore, the voltage Va applied to one input terminal of the operational amplifier 0PA3 is larger than the overload level value applied to the input side (the overload level value applied to this side), and the negative voltage is applied to the output side of the operational amplifier 0PA3, that is, the 0 point 1. Occur.

Therefore, since a negative voltage is applied to the base f of the transistor TR1, the transistor TR1 is turned off.

When transistor TR1 turns off, transistor TR
The base current of transistor TR2 stops flowing, and transistor TR2 also turns off.

Therefore, the power to the motor M is cut off, and everything is restored to the state before the power was applied.

When the camera's release button is pressed in this state, a picture is taken, and when the picture-taking operation is completed, the output command switch S is pressed again.
is turned on, and the above operation is repeated.

Next, if the film ends in the middle of winding, the operation starts as described above, but since the film stops midway, the motor Mf goes overboard in the middle of film winding. A load is applied, and an overcurrent flows through the motor M before time t2 in FIG. 2.

Therefore, Va becomes a large value, and the output of the operational amplifier 0PA3 is inverted, turning off the transistors TR1 and TR2, as in the case where the film loading is completed.
Cut off the power to motor M.

However, if the film ends just before the start of winding, a voltage corresponding to the steady current is not detected at point a, and an appropriate overload level cannot be set.
There may also be a case where the operational amplifier 0PA3 cannot perform normal f comparison operation.

However, in such a case, the operational amplifier OP A4
d is applied as a reference voltage, and this reference voltage Vd is compared with the voltage Va at point a. When va>d, the voltage at point i is , the potential changes from negative to positive.

When the voltage at point f becomes a positive voltage, the base-emitter of the transistor TR3 is forward biased, and the transistor TR3 is turned on.

Transistor TR3 is on (then transistor T
The base voltage of R1 becomes approximately O, and transistor TR1 is turned off.

Therefore, similarly to the above, the transistor TR2 is turned off, the power supply is cut off, and the energization of the motor M is stopped, returning to the initial state.

Also, even if the film does not end, camera malfunctions may occur.
When winding of the film is no longer performed, the transistor TR3 is turned on in the same way as described above, and the power supply to the motor M is stopped.

In addition, taking into consideration the above explanation, we have omitted the explanation of the operation of the operating power supply of the operational amplifier, but as shown in the figure, the transistor TR4, the capacitor C4 to the resistor R261R2□
, diode D1, coil L1, diodes D2-D,
The negative power supply circuit of the operational amplifier is configured by a DC-DC converter using a full-wave rectifier circuit, etc.
A negative voltage is supplied from PA○, and a positive voltage is supplied from OPA■ to each operational amplifier.

FIG. 4 shows another specific embodiment of the present invention.
The difference from the circuit in Fig. 3 is that the voltage applied to the + side input terminal of the operational amplifier 0PA2 is connected to the zener diode Z as shown in the figure.
The only difference is that the voltage V9 at point g is obtained by dividing the Zener voltage at D by resistors R29 and R3o, and the other configurations and functions are the same as those in FIG. 3, so their explanation will be omitted.

In this way, the voltage Vc at the 0 point becomes Vc - V11 + R'4 Vb, and Vc
A constant bias value is added to , and if Vc does not become R4/ times as much as b and the steady current during hoisting is relatively large, the overload level setting value may be excessive.
You can prevent this from happening.

As explained above, in the unconventional system, the overload level value is always set by 1 times the motor current under steady load, so for example, the load applied to the motor may vary depending on temperature changes or the type of film. Even if the film is not played due to an accident, the overload level will always be accurately detected. It is possible to prevent abnormal overload from being applied to the motor and camera body, and furthermore, the end of the film can be accurately detected and proper operation can be carried out at all times.

In addition, in the above explanation, when motor M1 is overloaded, the motor current is detected and the power is cut off. However, for example, if the load on motor M suddenly decreases, If the circuit is changed to a circuit that cuts off the electric field at the end of the film, it will be possible to easily detect when the film has run out in a camera using film.

Moreover, according to such a circuit, if a film cutting accident occurs, it is possible to easily detect the state of the film cutting not only in the case of a 35% film, but also in the case of a 35% film.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing an uncontrived embodiment, Fig. 2 is a diagram showing how the motor current flowing through the motor for film presentation changes over time, and Fig. 3 is a specific example of the uncontrived embodiment. FIG. 4 is a circuit diagram of an embodiment in which the embodiment shown in FIG. 3 is partially modified. DESCRIPTION OF SYMBOLS 1... Motor switching circuit, 2... Load current level detection circuit, 3... Timer, 4... Gate circuit,
5... Memory circuit, 6... Overload level setting circuit, 7... Comparison detection circuit, 8... Protection safety circuit,
E...Power supply, So...Power switch.

Claims (1)

[Scope of utility model registration request] In the camera's electric winding device, the film winding command is turned on by a motor switching circuit that energizes the film winding motor, a load current level detection circuit that detects the torque of the motor as a current level, and the motor switching circuit. A timer that starts a timed operation when the circuit is turned on and outputs an output signal after a certain period of time, a gate circuit whose gate is opened by the output signal of this timer and allows the output of the load current level detection circuit to pass through, and this gate circuit. is opened, a storage circuit that stores the output of the load current level detection circuit, an overload level setting circuit that converts the output of this storage circuit into an overload level value, and this overload level setting circuit (which sets a comparison detection circuit that compares the output of the load current level detection circuit with the output of the load current level detection circuit from the time the gate is opened, and turns off the motor switching circuit when the latter value becomes larger than the former value; An over/under detection device consisting of.