JPS6340558B2 - - Google Patents

Description

Detailed Description of the Invention The present invention enables constant high-speed operation by energizing a built-in clutch coil to press and engage the clutch friction member provided on the motor shaft side and the clutch lining provided on the output shaft side. The present invention relates to a sewing machine drive device having an electromagnetic clutch mechanism for transmitting the rotational force of a motor to an output shaft, which detects the wear margin of the clutch lining and performs a predetermined protective operation.

Conventionally, motors with the above-mentioned electromagnetic clutch structure have been mainly used as motors for driving sewing machines, and this causes accelerated wear of the clutch lining.
If the clutch connecting member carrying the clutch lining comes into contact with the clutch friction member, the speed of the output shaft may become unstable, or the metal may come into contact with metal at the pressure welding part, resulting in meshing. Eventually, the speed could not be controlled, and in some cases, it would rotate at high speed and would not stop, making it dangerous for sewing work. As mentioned above, the temperature rises significantly due to metal-to-metal contact, which is dangerous.On the other hand, the friction member of the clutch may be damaged due to metal-to-metal contact, which may require repair, which is a problem in terms of after-sales service. There were also problems.

However, the current situation is that no countermeasures have been taken to address the above-mentioned drawbacks.

The present invention detects the above-mentioned wear allowance before metals come into contact with each other, and if the wear allowance is abnormally large, it notifies the sewing manufacturer, eliminates the above-mentioned danger or malfunction, and provides a safe electromagnetic drive device. That is.

FIG. 1 shows an example of the structure of the motor and the electromagnetic clutch mechanism used in the present invention, and the structure will be explained according to the drawing.

A flywheel 1 is fixed to a motor shaft 2 and constantly rotates at high speed. A clutch friction member 3 made of magnetic metal is attached to the flywheel 1.
A magnetic circuit shown by a broken line is formed between the clutch fixing iron core 4 and the clutch connecting member 5 made of magnetic metal, and the excitation of the clutch coil 6 generates a magnetic flux φ _A. The clutch lining 7 is usually made of cork and is adhered to and carried by the clutch connecting member 5. The clutch connecting member 5 is movable on a spline shaft 9 fixed to the output shaft 8, with the thrust direction being free and the rotational direction being fixed.

A brake mechanism consisting of a brake coil 10, a brake fixed iron core 11, a brake friction member 12, a brake lining 13, and a brake connecting member 14 is arranged symmetrically with the clutch mechanism, and when the brake coil 10 is excited, φ _B is obtained. Magnetic flux is generated as shown by the broken line.

The operation configured as described above is performed as follows.

First, when the clutch coil 6 is energized, a magnetic flux φ _A is generated, and the clutch connecting member 5 moves toward the clutch friction member 3 which is constantly circuited at high speed, and the clutch lining 7 is pressed into contact with the clutch friction member 3. The rotational force is transmitted to the output shaft 8 via the clutch connecting member 5 and the spline shaft 9, and the output shaft 8 is rapidly accelerated.

On the other hand, when the speed increases higher than the set speed, the brake coil 10 is excited and a magnetic flux φ _B is generated as shown by the broken line, the brake connecting member 14 moves toward the brake friction member 12, and the brake lining 13
The static force is transmitted to the output shaft 8 via the spline shaft 9, and the output shaft 8 is decelerated.

In this way, a predetermined speed can be obtained, but in normal stable operating conditions, the excitation force of the clutch coil 6 is adjusted, and therefore the magnetic flux φ _A is adjusted to increase the speed at the surface of the clutch lining 7. The operation is performed so that a constant speed is maintained by adjusting the pressure contact force and creating an appropriate slippage.

As mentioned above, since the clutch lining 7 is constantly sliding on its surface and its speed is controlled, wear is inevitably accelerated, and eventually the height Gc ( (hereinafter referred to as clutch lining height) is 0
As a result, the clutch friction member 3 and the clutch connecting member 5 come into direct contact with each other, and as mentioned above, heat is generated, resulting in a dangerous situation, and due to their engagement, the engine may not be able to stop at high speed. There was a risk of an abnormal situation.

In the present invention, a predetermined wear amount of the clutch lining 7 is detected before entering the abnormal state,
This system not only informs the operator of the dangerous situation, but also prevents the dangerous situation from occurring.

Here, wear of the brake lining 13 accelerates as well, but since the other brake friction member 12 that is press-fitted is always stationary, there is no danger, or as mentioned above, the intermediate speed operation is usually performed on the clutch side. The object of the present invention can also be achieved by a method of detecting only a specified wear amount of the clutch lining 7, since the clutch lining 7 wears out more quickly than the clutch lining 7. An example of this will be explained below using FIG. 2.

In Fig. 2, numeral 15 indicates a speed setting circuit, which converts the depression position of the sewing machine pedal (not shown) into an electrical signal using a combination of a magnet and a magnetic sensor, or a shield plate and an optical sensor, etc., and starts the sewing machine. Outputs a command signal P _D and a speed setting signal P _S. 16 is a control circuit, which is a logic centering on a microcomputer (hereinafter referred to as microcomputer).
Consists of an IC circuit. 17 is a wear detection circuit, which is composed of a circuit centered on an OP amplifier IC as described later, and is configured to detect the clutch lining height Gc.
This is a circuit that measures whether or not the value has reached a specified value.
18 is a motor that is constantly rotating; 19,
Reference numerals 20 denote drivers for the clutch coil 6 and brake coil 10, respectively, which start and stop the sewing machine 21. 22 indicates a needle position detector that outputs a pulse signal Nu corresponding to the needle position of the sewing machine;
Reference numeral 3 denotes a speed detector which detects the speed of the sewing machine and outputs an actual speed signal F _G to the control circuit 16.

FIG. 3 shows a normal sewing operation in the form of a time chart, and the normal sewing operation will be described below with reference to FIGS. 2 and 3.

First, when the sewing machine pedal is depressed, a sewing machine start command signal P _D is output, and the control circuit 16
excites the clutch coil 6 via the driver 19, the sewing machine 21 rapidly accelerates, and the speed detector 23
The actual speed signal _FG starts to be output to the control circuit 16.

The speed of the sewing machine 21 is determined by the speed setting circuit 15.
When the speed becomes higher than the speed set by the speed setting signal P _S from the driver 20, the brake coil 10 is excited via the driver 20, and the sewing machine 21 is operated to be decelerated, and the sewing machine 21 is operated to be normally stable. During operation, a constant speed is maintained only by excitation of the clutch coil 6.

Next, when the start command signal P _D from the speed setting circuit 15 switches to a stop command, the control circuit 16 first switches to a low speed setting, and the sewing machine 21 is rapidly decelerated. After the sewing machine 21 reaches the low speed N _P , the needle position detector 22 detects a predetermined needle position and outputs a needle position signal.
When Nu is output, the control circuit 16 excites the brake coil 10 for a certain period of time, and the sewing machine 21 stops at a predetermined needle position.

The above description has been about normal sewing, but next, the process when the clutch lining height reaches a specified value or less will be explained with reference to FIGS. 4 and 5.
FIG. 4 shows a flowchart of the microcomputer included in the control circuit 16, and FIG. 5 shows the operation at that time.

In FIG. 4, first, 24 indicates the start command signal.
It is checked whether P _D is input to the microcomputer and the specified wear of the clutch lining is detected. If the wear is not detected, normal sewing is performed, and if not, the following abnormality processing is performed. will be carried out.

That is, as shown in 25, a predetermined number of stitches A, for example, several stitches, is preset in a built-in counter, and the clutch coil is energized to perform speed control at a low speed N _P , and at the same time,
Start counting the number of stitches A mentioned above.

FIG. 5 shows a case where the counting is performed at the trailing edge of the needle position signal Nu and the number of stitches A is three.

After the above-mentioned counting of the number of stitches A is completed, as shown in 26, at the time when the needle position signal Nu is detected, the sewing machine stops even though the start command signal P _D is output. .

As described above, when wear of the clutch lining exceeding a specified value is detected, from the time when the pedal start signal P _D is output, the sewing machine starts
Constant low speed N _P that does not follow the speed setting signal P _S
The machine is driven by the clutch connecting member 5 or the brake connecting member. A series of repair work will be carried out, such as replacing 14 with a new one.

Here, the method of notifying the operator of wear through the operation of the sewing machine is the most reliable method compared to other methods, such as using light or sound.
Note that since the sewing machine described above is operated at a low speed N _P , it can be said that there is no danger.

Next, FIG. 6 shows a specific example of the construction of the wear detection circuit, and FIG. 7 shows its operation in the form of a time chart, and the following description will be given with reference to the same figures.

In FIG. 6, +V _DD represents the DC power supply voltage for driving the clutch coil 6, and +V _CC represents the DC stabilized power supply voltage for driving the IC circuit. Further, 27 indicates a microcomputer which is included in the control circuit 16 and plays a main role in its control, as described above, and IC1 is an inverter IC which switches the transistor TR1 through the diode D1 to drive the clutch coil 6. Note that the diode D2 and the resistor R1 are a flywheel circuit for suppressing the abnormal voltage generated at the collector when the transistor TR1 is turned off and protecting the transistor.

The voltage across the resistor R2 connected to the emitter of the transistor TR1 is the voltage across the resistor R2 connected to the emitter of the transistor TR1.
1 changes in proportion to the current flowing through the clutch coil 6 when the clutch coil 6 is turned on. The resistance R2 and the resistance R
3, R4, R5 and the OP amplifier IC IC2 constitute a current measuring circuit, which outputs a signal Va obtained by amplifying the signal representing the current to the clutch coil 6 to a required level. Also, resistors R6, R7,
R8, variable resistor VR1, and OP amplifier IC IC3
constitutes a comparison circuit, and when the signal Va reaches the voltage Vc set by the variable resistor VR1,
The output Vb of the IC3 is inverted.

The operation for detecting the clutch lining height Gc configured as described above is as follows.

First, the microcomputer 27 excites the clutch coil 6 for a time T. After the time T has elapsed, the microcomputer 27 determines that if the input signal Vb is "H", it is "normal", and if it is "L", it is "small gap".

The principle of detecting the gap described above is as follows.
That is, the inductance L of the clutch coil 6 changes in proportion to the permeance P of its magnetic circuit, and the permeance P changes greatly in accordance with changes in the gap distance unless there is magnetic saturation in the iron core. In other words, the smaller the gap, the larger the permeance P, and the smaller the inductance L.
changes as it becomes larger. On the other hand, the time constant τ, which is a measure of the rise time of the excitation current of the clutch coil 6, is expressed by τ=L/R, and since the series resistance R in this equation is constant, it can be said that τ is proportional to the inductance L.

Therefore, when the clutch lining height Gc to be detected is set using a jig or the like,
If the signal Va after the elapse of time T is set in advance to match the reference voltage VC as shown by the chain line in Figure 7, it will be possible to detect when the wear has accelerated and the specified value has been reached during normal use. .

Here, when the clutch coil 6 is energized for the time T mentioned above, a phenomenon occurs in which the output shaft 8 slightly rotates, but as a countermeasure to this, the brake coil 10 is energized while the clutch lining height Gc is being measured. The present invention can be realized more effectively by using this method.

Further, normally the wear of the lining 7 does not occur suddenly, so the determination is made once immediately after the power is turned on, and thereafter the control circuit 16 drives the sewing machine according to the flowchart shown in FIG. It can be said that this method is one effective means for realizing the present invention.

As described above, the present invention treats the change in permeance due to the change in the clutch lining height Gc as a change in the inductance of the coil, and therefore calculates the change in the time course of the excitation current to the clutch coil over a predetermined period of time. Detecting the clutch lining height Gc by detecting after T,
If the Gc is detected to be below a specified value, the sewing machine is notified by the operation of sewing several stitches at low speed N _P and then stopping, thereby preventing the risk of heat generation or runaway output shaft as in the past. It is advantageous in servicing because it can prevent damage before it occurs and can detect it before the clutch friction member surface is damaged.Moreover, it has a simple circuit configuration.
This has the great effect of being able to be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an electromagnetic clutch motor used in a sewing machine drive device, FIG. 2 is a block diagram showing the basic configuration of the sewing machine drive device of the present invention, and FIG. 3 is an operational explanatory diagram showing the normal operation of the device. Fig. 4 is an explanatory diagram showing the operation of the microcomputer used in the same device, Fig. 5 is an explanatory diagram showing the operation when detecting wear on the lining of the same device, and Fig. 6 is an explanatory diagram showing the operation of the microcomputer used in the same device. The circuit diagram and FIG. 7 are operation explanatory diagrams showing the wear detection operation of the circuit. 1...Motor shaft, 3...Clutch friction member,
4...Clutch fixed iron core, 5...Clutch connecting member, 6...Clutch coil, 7...Clutch lining, 8...Output shaft, 15...Speed setting circuit,
16... Control circuit, 17... Wear detection circuit, 18
... Motor, 21 ... Sewing machine, 22 ... Needle position detector, 23 ... Speed detector.

Claims (1)

[Claims] 1. A motor that constantly operates at high speed, a clutch mechanism that transmits the rotational force of the motor to the output shaft through the clutch friction member, clutch lining, and clutch connecting member by energizing the clutch coil, and the wear allowance of the clutch lining. a wear detection means for detecting the sewing machine; a speed setting means for issuing a stop command or setting a speed ranging from low speed to high speed; a control means for controlling the sewing machine in accordance with a speed setting signal from the speed setting means; It consists of a speed detector that detects the speed and a needle position detector that detects the needle position and outputs a needle position signal, and the wear detection means detects that the wear amount of the clutch lining has reached a specified value. At this point, the control means performs low speed operation without following the speed setting signal from the speed setting means, and presets a prescribed value A in a counter included in the control means to count the needle position signal. The sewing machine driving device is configured to start the sewing machine and stop the sewing machine at a position corresponding to the needle position signal when the specified value A has been sewn.