JPS6356124B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a conveyor and ancillary equipment protection device.

Conventionally, protection devices such as shear pin types, floating types, and time-limited relay types installed on conveyors are mainly intended for overload protection of conveyor chains (protection against heavy overloads that may lead to chain breakage, etc.). However, in operating processes that use conveyors, such as painting processes and cleaning processes, if the conveyor or the conveyed object interferes with ancillary equipment such as automatic painting machines or automatic washing machines, even if the conveyor does not become overloaded, the said ancillary equipment An excessive force that is smaller than that in the case of the overload may be applied to the conveyed object, which may cause damage to incidental equipment and the like. In this case, conventional protection devices may operate if the conveyor is under heavy load, but cannot protect when the conveyor is under light load.

In order to solve this situation, the present invention detects the current of the conveyor drive motor to distinguish between conveyor overload and load increase due to interference with the above-mentioned auxiliary equipment, and provides a conveyor with protection functions for each. To provide a protective device for incidental equipment.

In order to achieve the above object, the present invention has been developed so that the current of an induction motor for driving a conveyor falls within a heavy load range defined by the intermediate value between the maximum actual load current (the current at the maximum load of the conveyor) and the no-load current. It discriminates which of the light load range it is in, and according to the discrimination result, it switches between a protection device that protects the conveyor and a protection device that protects ancillary equipment. The feature is that a dead zone does not occur in the area.

Embodiments of the present invention will be described below with reference to the drawings.

Fig. 1 shows the overall connection diagram of the device of the present invention, in which the main circuit of a three-phase induction motor 1 for driving a conveyor connected to a power source S is connected to contacts MG of an electromagnetic switch MG and three CTs.
2, 2h, and 2l, and connect the discrimination switch 3, heavy load protection device 4H, and light load protection device 4L to the control circuits u and v.

The discrimination switch 3 inputs the secondary current of the CT 2 and starts the first relay 5 or the second relay 6 depending on whether the current of the motor 1 belongs to a heavy load range or a light load range, which will be described later. Energize after an hour.

Heavy load protection device 4H and light load protection device 4L are
Input the secondary current of CT2h or 2l respectively,
These inputs are normally short-circuited by the normally closed contacts rh and rl of relays RH and RL, respectively, and are in an inactive state. However, when the discrimination switch 3 is activated and the relay RH or RL is energized by the relay 5 or 6,
Contact rh or rl opens and becomes operational. In the operating state, the protection device 4H energizes the auxiliary relay AH when the motor current exceeds the maximum actual load current that is less than the rated current and flows for a set time or more. Similarly, the protection device 4L energizes the auxiliary relay AL when the motor current exceeds the set excessive value in the light load state and flows for a set time or longer. The normally closed contacts ah and al of the auxiliary relays AH and AL are connected in series with the starting device 7, the electromagnetic switch MG and its overcurrent relay contact olr, and the contact ah
Or when al opens, the electric motor 1 stops.

FIG. 2 shows the block circuit of the discrimination switch 3.
The secondary current of CT2 is rectified and converted into a load current signal by the current detection circuit 8, and this is sent to the heavy load comparator 9.
and the light load comparator 10.

The operating current setting device 11 is used to set the intermediate value t of the actual load current range of the motor 1. If the maximum actual load current is 80% of the rated current, the no-load current is approximately 30% of the rated current. Therefore, the intermediate value is set to, for example, a signal level corresponding to 55% of the median value. However, the intermediate value can be set as appropriate depending on the conditions of the conveyor, the conveyed object, ancillary equipment, etc.

The upper limit current circuit 12 and the lower limit current circuit 13 each output a first current signal h that is several percent larger than the intermediate value t, and a second current signal l that is also smaller, and compare the signals Ih and Il, respectively. Vessels 9, 10
Compare with signal I at. As shown in FIG. 3, when the signal I is less than Il, the comparator 10 does not output and the relay 5 is de-energized, but the comparator 9 outputs and energizes the relay 6. . When the signal I increases and reaches point A, the comparator 10 outputs an output and the relay 5 is energized after a time equal to or longer than the motor starting time. Further, when the point B is reached, the comparator 9 has no output and the relay 6 is deenergized. Next, when the signal I decreases to below point C, the comparator 9 outputs an output and the relay 6 is energized after a time equal to or longer than the motor startup time.When the signal I decreases further to point D, the comparator 10 loses its output and the relay 5 disappears. The reason why the energization of the relay 6 is delayed by more than the motor starting time is as follows.

Generally, an electric motor overload protection device is set not to operate during the electric motor startup time. However, even if the load current signal I becomes smaller than the first current signal Ih after the start-up time, it may not continue to decrease and may become larger than Ih again. In this case, I<
If the Ih time is as short as a few seconds, it is reasonable to conclude that the conveyor is in a heavy load state, so the switch to the light load state is not performed immediately, but is delayed for at least the startup time. It is done from

As mentioned above, Ih and Il are used to switch relays 5 and 6.
The two switching levels are provided for protection device 4.
This is to prevent H and 4L from operating within the motor startup time and to prevent a dead zone from occurring during switching.

Figure 4 shows the block circuit of the protection device 4H or 4L, 14 and 15 are comparators, and 16 is a variable resistor.
This is a delay circuit having Rv and a capacitor C.

In the case of the protection device 4H, the signal I and the motor rated current signal _I1 are input to the comparator 14, and the output of the comparator 14 when I> _I1 is integrated in the delay circuit 16, and the charging voltage of the capacitor C is The time required for the signal I to reach the reference signal Is is set as the permissible time for the signal I, that is, the permissible time _t1 for an overload current exceeding the rated current. At that time, comparator 15 outputs an output after the above-mentioned allowable time to energize auxiliary relay AH.

In the case of the protection device 4L, the comparator 14 receives the signal I and a set current signal that is less than the maximum actual load current signal of the motor.
I ₂ and the time it takes for the charging voltage of capacitor C to reach the reference signal Is. The allowable duration time _t2 is set.

Other points are the same as in the case of the protection device 4H. However, _t2 shall be within the switching time of the discrimination switch 3. This is because if t ₂ is larger than this, the signal I will exceed Ih and the protection device 4L will become inactive before it is activated. When the motor current continues for more than the time _t2 defined above, comparator 15 outputs and energizes auxiliary relay AL.

Electrical protection devices for electric machines that include protection devices 4H and 4L with a circuit that prohibits operation during motor startup time are commercially available, so if this is used, ordinary relays can be used as relays 5 and 6.

The present invention has the above configuration, and provides protection against overload exceeding the rated output of the conveyor drive motor, that is, the risk of damaging the motor or the conveyor, and protection against the risk of damage to the conveyor ancillary equipment due to interference with the conveyor or conveyed objects. This is achieved by detecting the motor current, and has the effect of quick recovery after activation of the protection device.Furthermore, there is no unprotectable dead zone between the protection range of the former and the protection range of the latter. The effect is that it can operate with a continuous protection range. In addition, ready-made devices can be used as the protection devices that share each protection range, and the discrimination switch has a simple structure, so there is an advantage that it can be manufactured at low cost.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is an overall circuit diagram, FIG. 2 is a block circuit diagram of a discrimination switch,
FIG. 3 is an explanatory diagram of the operation of the first and second relays, and FIG. 4 is a block circuit diagram of the heavy and light load protection device. 1... Induction motor for conveyor drive, 3... Discrimination switch, 4H... Heavy load protection device, 4L... Light load protection device, 5... First relay, 6... Second,
MG...Control device, I...Load current signal, _I1 ...
Rated current signal, I ₂ ... Setting current signal, It ... Intermediate setting value signal, Ih ... First current signal, Il ... Second
current signal.

Claims (1)

[Claims] 1 A first current signal that is slightly larger and a second current signal that is slightly smaller than an intermediate setting value signal between the maximum actual load current signal and the no-load current signal of the induction motor for driving a conveyor are respectively set to the load current of the motor. When the load current signal increases more than the second current signal, the motor is energized with a time limit longer than the starting time of the motor, and when the load current signal becomes smaller than the second current signal, the motor is deenergized. a first relay; and a second relay that deenergizes when the load current signal becomes greater than the first current signal and energizes with the time limit when the load current signal decreases less than the first current signal. a heavy load protection device that is activated by energizing the first relay and outputs the load current signal when the rated current signal of the motor exceeds a set allowable time; and energizing the second relay. a light load protection device that is activated and outputs a set current signal in which the load current signal is smaller than the maximum actual load current signal for a set permissible time; and an output of the heavy load protection device or the light load protection device to protect the motor. A protection device for a conveyor and ancillary equipment having a control device for stopping the conveyor and ancillary equipment.