JPS61236311A - Torque limiter of conveying motor in conveying apparatus - Google Patents

Abstract

PURPOSE:To suppress an impact force at stopping time by switching the set level of a torque limiter to a low level when a rotating speed signal substantially comes to constant value and a low speed feed designation signal is input. CONSTITUTION:An instruction unit 22 outputs a speed command value V on the basis of an operation designation signal from a sequence instruction unit 20 and a speed set value from a speed setter 21. A differential amplifier 23 applies a control signal in response to a deviation between a speed command value V and a speed signal to a power amplifier 2. A torque limiter 28 applies a signal voltage -V' of the prescribed value indicated in advance when a current I flowed to a conveying motor 10 exceeds the prescribed level to limit a current I. A torque limiter switch 40 outputs a switching signal S5 when a speed signal comes to substantially constant value and a low speed feed designation signal from the unit 20 is output, thereby reducing the limit value of the limiter 28.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a torque limiting device for a conveying motor in a conveying device installed, for example, in an assembly line for automobile bodies, and more specifically, a torque limiting device for a conveying motor of a variable speed amount. This is a transport device that switches the transport speed from high speed to low speed while applying K feed (a transport unit carrying a vehicle body to be assembled, etc.), and then stops this transport unit by pressing it against a stopper, and the shaft of the transport motor The present invention relates to a conveyance device equipped with a torque limiter that regulates the current flowing through the motor according to a set level in order to limit the torque to a predetermined value or less.

(Prior Art) FIG. 4 illustrates a conventional conveyance device equipped with the torque limiter.

In the figure, 1 is a transport unit, 2 is a rack attached to this transport unit, 3 is a rank binion meshed with this rank, and 4 and 5 are front (right side in the drawing) and rear of the transport unit. Shock absorbers 16 and 7 attached to the left side (same as above) are a forward limit stopper and a backward limit stopper respectively attached to the fixed bed 8.

Reference numeral 10 denotes a reversible/variable conveyance motor, and the rank pinion 3 is driven from this conveyance motor in forward and reverse directions via a reduction gear 11 and a mechanical torque limiter 12, whereby the conveyance unit 1 is fed forward and backward. After this conveyance unit is decelerated before reaching the forward limit or the backward limit, it is pressed against the forward limit stopper 6 or the backward limit stopper 7 via the shock pumper 4 or 5, respectively, and is stopped. 13 and 14 are a forward limit sensor and a backward limit sensor of the transport unit, respectively, and 15 and 16 are the forward deceleration position sensor and backward deceleration position sensor, respectively.

On the other hand, 20 is a sequence indicator, and based on the position signals detected by the sensors 13 to 16, the relay 20f
, 20r, 20h, and 20k output operation instruction signals for forward, backward, high-speed feed, and low-speed feed, respectively. 21 is a speed setting device, and the above-mentioned high and low feeding speeds are set in this setting device 21. 22 is a direction and speed command device, and a sequence command device 20
The rotational direction of the transport motor 10 at the time of startup is commanded by the operation instruction signal and the speed value set in the speed setting device 21, and the speed command is performed by outputting a voltage V according to the speed value.

This speed command signal voltage V is input to the power amplifier 24 via the amplifier 23 . The power amplifier 24 controls the current I flowing through the transport motor 10 by performing, for example, phase control based on this input, and controls the current I flowing through the transport motor 10.
Rotate at high or low speed. The rotational speed is detected by a rotational speed detector 26 using, for example, a tacho generator, and the detected value (voltage) is transmitted to the differential amplifier 23.
feedback control is performed so that the deviation from the signal voltage V of the speed command is reduced to zero.

Therefore, the conveyance motor 10 rotates at a predetermined rotational speed, either high or low, according to the command from the command unit 22.

27C is a current sensor that detects the current flowing through the transport motor 10, and 28 is a torque limiter configured using a comparison circuit, etc., in case abnormal resistance occurs in the transport unit 1 and it suddenly stops. That is, when the current flow becomes excessive and the output of the current sensor 27 exceeds a predetermined level,
Torque limiter 28 detects this state and outputs a signal voltage -V' of a predetermined value instructed in advance. Then, the power amplifier 24 adds this signal voltage -V' to the signal voltage V to lower its output. Since the electric current is limited by this, the conveyance motor 10 is controlled by the torque limiter 12.
protected against overcurrents in cooperation with

FIG. 5 is a graph showing the above-mentioned operation when transporting the transport unit 1 forward.

Now the relays 20f1 and 20 of the sequence indicator 20
h is closed and the forward and high-speed feed command signals Sf and sh are output as shown in A in the same figure, and at the same time, as shown in B in the same figure,
As shown in Figure B, the signal voltage V of the command unit 22 rises at a high potential ■1 in the acceleration period Xo - (omitted). Therefore, forward/high speed feed is applied to the transport unit 1, and this is the deceleration position X.
2, the position signal from the forward deceleration sensor 15 opens the relay 20h and closes the relay 20h, causing a low-speed feed command signal S! is issued, and at the same time, the signal voltage V of the command unit 22 falls from vh to ■ through the deceleration section X2 to X3 (period T2). Therefore, the transport unit 1 is fed at low speed, and when it reaches the forward limit X4, the forward limit stopper 6
The forward limit sensor 13 detects this state. After this sensing, a predetermined timer amplifier period T3
When , the relays 20f, 20-6 open, the command signal Sf, 8.6 disappears, and at the same time, the signal voltage V becomes zero.

Figure C shows the state of the electric current flowing through the conveyance motor 10, which exhibits a positive beat II in the acceleration section XO-Xl, and then almost partially changes to the value 2, and after passing the forward deceleration position X2. A negative peak value of 3 is exhibited, and then approximately a part of the value of 4 (I2>I4) is maintained until reaching the forward limit X4. Thereafter, during the timer up period T3, as the transport unit 1 is stopped, the rotation of the transport motor is restricted while being excited, so that the current I suddenly decreases and rises, and a positive beak error 5 occurs again.

Ih shown in FIG. C is an upper limit current value regulated based on the signal voltage -V' of the torque limiter 28, and this upper limit current value is higher than the peak Il because it does not restrict the starting current of the transport motor 10. Set to high.

The reason why the timer up period T3 is provided is that even after the transport unit 1 collides with the forward limit stopper 6, the shaft torque is applied for a while, thereby preventing the unit from bouncing back and reaching the forward limit. This is to ensure that it stops.

The above operations are the same in the case of backward feeding.

(Problem) Although such a conveyance device has the advantage of being able to stop the conveyance unit in a fixed position using a simple mechanical means such as a stopper, it has the disadvantage that the conveyance speed is restricted. . The reason is as follows.

That is, when the conveyance unit is pressed against the forward limit or backward limit stopper, the pressing force due to the shaft torque of the conveyance motor acts impulsively on the stopper in addition to the impact force from the conveyance unit.

This is because, as mentioned above, the upper limit value of the electric current flowing to the transport motor must be set to a high level, so that the peak I5 rises to a high level at the beginning of the timer amplifier period, and correspondingly, the current flow to the transport motor increases. This is because the shaft torque increases rapidly.

For the above reasons, these stoppers or the fixed bed fatigue early, and it is often impossible to remove and reinforce them due to space constraints.

Therefore, in order to prevent early fatigue, it is necessary to limit the speed of low-speed feed, and accordingly, the speed of high-speed feed is also restricted.

Therefore, an object of the present invention is to suppress the impact force at the time of stopping even if the feeding speed is increased.

(Means of the Invention) The means of the present invention which solves the above-mentioned problems distinguishes the state of the rotation speed detector of the conveying motor and the state when the detected value of the rotation speed detector becomes almost a constant value, and generates a discrimination signal. It is equipped with a discriminator that outputs an output, and a torque limit switch that outputs a switching signal when this discrimination signal and at least a low-speed feed instruction signal are input, and sends this switching signal to the torque limiter to change the setting level. The switch is made to switch to a lower position.

(Function) According to the above means, when the detection value of the rotational speed detector becomes approximately fixed in the low speed feed region, that is, when the conveyance unit is fed at low and constant speed, collision with the stopper occurs.
When ready, the torque limit switch outputs a switch signal which causes the torque limiter to switch its current setting level to a lower level. Therefore, the upper limit of the current flowing through the transport motor is further regulated to a lower level. Therefore, the peak of the current that occurs during the timer up period is cut off at the regulated upper limit, and as a result, the shaft torque of the transport motor is suppressed. Therefore, by appropriately setting this upper limit value, the shaft torque can be suppressed to an extent that can suppress the rebound of the transport unit.

(Embodiment) FIG. 1 shows an embodiment of the present invention, and the device of this example has a discriminator 30 and a torque limit switch 40 compared to the conventional device.
In addition to additionally installing the rotation speed detector 26, the rotation speed detector 26 is also used.

The discriminator 30 is configured using, for example, a differential circuit, and when the conveyance motor 10 changes at a constant rotational speed after being accelerated or decelerated as described above, that is, the rotational speed detector 26
When the detected value of is approximately a constant value, the determination signal Sl is output.

FIG. 2 shows an example of the torque limit switching device 40. In the same figure, 41 is an AND gate, which is output when the low-speed feed instruction signal Sl from the sequence indicator 20 and the discrimination signal 81 are input, and this output is outputted as a switching signal S3 via a delay timer 42. . The delay timer 42 is set with a delay time corresponding to the timer amplifier period T3, so that even if the transfer motor stops and the discrimination signal S1 disappears, the output state of the discrimination signal S3 remains until the period T3 elapses. is retained.

This embodiment also includes another AND gate 43, which outputs a switching signal S4 when the high-speed feed instruction signal sh and the discrimination signal S1 are input.

Reference numeral 44 denotes a delay timer with an input circuit trap for the instruction signal sh, and this delay timer has a timer corresponding to the acceleration period T1;
This also sets a somewhat large delay time. 45 is an OR gate which outputs a switching signal S5 while the switching signal S3 or S4 is input, and sends this signal S5 to the torque limiter 28 to determine the supply value of the output signal voltage -V' of the limiter. Switch to something bigger. This lowers the current upper limit value set by the power amplifier 24. FIG. 3 shows this embodiment.

This figure corresponds to the above-mentioned figure 5C, and the acceleration section Xo
-XI (acceleration period Tl), the transport motor 10
The upper limit of the electric current flowing into the current is still at the high level Ih
When the delay timer 44 becomes conductive and the switching signal 54 (85) is output, the switching signal 5a (S
s) is output, and the current upper limit value is regulated in the same way as above. In this example, these upper limit values I2 and p are set to the same value, but it is also possible to set IA'>XA according to the current values p and p during high-speed and low-speed feeding, respectively.

In this way, the electric current is regulated by its upper limit and changes through positive peak Il, constant value Ia, negative peak Ia, constant value ■4, etc., and then when the transport unit 1 collides and stops,
Since the current I at this time cannot rise above the upper limit value k, the shaft torque of the transport motor 10 also does not rise.

As described above, in the embodiment, the current upper limit value is switched to a low value during high-speed feeding, so that when resistance occurs in the transfer unit, the transfer motor can be more protected from overcurrent than before.

(Effects) As explained above, the present invention suppresses the rapid increase in the shaft torque of the transport motor when the transport unit is stopped, thereby alleviating the impact, so it is possible to increase the feed speed by that amount. This can reduce takt time and increase operating efficiency.

[Brief explanation of the drawing]

Fig. 1 is an overall explanatory diagram showing one embodiment of the present invention, Fig. 2 is a detailed explanatory diagram of the main parts of Fig. 1, Fig. 3 is an explanatory diagram of the operation of the present invention, and Fig. 4 is an overall illustration of the conventional device. The explanatory diagram, FIG. 5, is an explanatory diagram of the operation of the apparatus shown in FIG. 4. 1...Transportation unit 6...Advance limit S)7 paT・
・Reverse limit stopper 10 ・Transport motor 26 ・・
・Rotation speed detector 28...Torque limiter 30...
Discriminator 40...Torque limit switch

Claims (1)

[Claims] A conveyance device that uses a variable speed conveyance motor to feed a conveyance unit, switches the feed speed from high speed to low speed, and then presses the conveyance unit against a stopper to stop the conveyance unit. In a device equipped with a torque limiter that regulates the current flowing through the motor according to a set level in order to limit the torque to a predetermined value or less, the detection value of the rotation speed detector of the conveyance motor and the rotation speed detector are approximately constant values. This switching device is equipped with a discriminator that discriminates this state and outputs a discrimination signal when this occurs, and a torque limit switch that outputs a switching signal when this discrimination signal and at least a low-speed feed instruction signal are input. A torque limiting device for a conveying motor in a conveying device, which inputs a signal to a torque limiter to switch the setting level to a lower level.