JPH085135B2 - Electric welding equipment - Google Patents

Description

TECHNICAL FIELD The present invention relates to a surface of a joint member that comes into contact with a pipe member when joining a pipe member made of a thermoplastic resin and a joint member also made of a thermoplastic resin. The present invention relates to an electric welding device in which a heating element is provided, and an electric current is supplied to the heating element to weld the pipe member and the joint member, and more specifically, an abnormal welding of the pipe member and the joint member is detected. Related to the device.

(Prior Art) Conventionally, various devices have been proposed for detecting abnormal welding of a pipe member and a joint member.

The welding abnormality referred to here is, for example, that both ends of the pipe member are not fully inserted to the depth of the joint member, or the insertion tip of the pipe member is cut obliquely,
When a gap is generated between the tips of both pipe members inserted into the joint member, it means an abnormality that occurs when the heating element is energized in this state.

That is, in the part where the pipe member is not inserted,
The heating element provided on the surface of the joint member may not move with the melting of the resin, resulting in a short circuit.
For this reason, the resistance value becomes small, so that the current flowing through the heating element increases, and as a result, sufficient welding strength between the pipe member and the joint member cannot be obtained.

As a conventional electric welding device for detecting such a welding abnormality, for example, JP-A-61-274920 (hereinafter referred to as Reference 1) and JP-A-62-116128 (hereinafter referred to as Reference 2) are disclosed. Things have been proposed.

The device shown in Reference 1 measures the current flowing through a heating element provided in a pipe joint at regular time intervals in order to monitor abnormalities in the welding process. When the measured data exceeds a certain range from the data at the time of normal welding, it is judged to be abnormal.

In addition, the device shown in Reference 2 constantly monitors changes in the supply current as a method for detecting a welding abnormality, and compares the current value measured immediately before and the current value measured this time at any time. When the current value has increased more than the previous current value, it is judged as abnormal.

(Problems to be Solved by the Invention) However, in the electric welding device of the above-mentioned reference 1,
The current data of the normal welding process must be stored in advance in the memory of the computer, but this data must be prepared for each heating element and for each time, so the amount of data stored in the memory is enormous. There was a problem that became. Further, the resistance value of the heating element changes depending on the outside air temperature at the time of welding, and the current value flowing through the heating element also changes accordingly.

In addition, the electric welding device of Reference 2 is to compare the current value measured immediately before and the current value measured this time, as occasion demands.
If the current increases little by little, it is difficult to determine the abnormality.

The present invention has been made in view of the actual situation, and its object is to always store the minimum value of the measured value of the current flowing through the heating element, and determine that the welding abnormality occurs when a current larger than the minimum value flows. By doing so, it is an object of the present invention to provide an electric welding device that enables more accurate detection of normal welding.

(Means for Solving the Problems) In order to solve the above problems, the present invention provides a joint member that comes into contact with a pipe member when joining a pipe member made of a thermoplastic resin and a joint member made of the same thermoplastic resin. A heating element is provided on the surface of, and in the electric welding device for welding the pipe member and the joint member by supplying an electric current to the heating element, current measuring means for measuring a current supplied to the heating element, While temporarily storing the first measured value by the current measuring means, when the current value measured by the current measuring means after a predetermined time is smaller than the previous measured value temporarily recorded, by updating the stored content, Storage means for storing the current measured value as the minimum value, a current value indicating the minimum value stored in the storage means, and a current value measured after a predetermined time. And when the current value measured after a predetermined time is larger than the current value showing the minimum value stored in the storage means, a counting means for counting plus 1 is provided, and one or more of the counting means are provided. When the number of times is counted up, it is determined that the welding abnormality of the pipe member and the joint member.

(Operation) The supply current to the heating element measured by the current measuring means is once stored in the storage means as a comparison reference value when the measurement is the first measurement. Then, the current value measured by the current measuring means after a predetermined time is compared with the previous current value stored in the storage means, and the current value measured this time is smaller than the previous current value according to the comparison result. Sometimes, by updating the stored content, the current value of this time is stored in the storage means as the minimum value. And
As a result of comparing the current value showing the minimum value stored in the storage means with the current value measured after the predetermined time, the current value measured after the predetermined time shows the minimum value stored in the storage means. When it is larger than 1, the count means increments the plus one. Then, when the counting means counts up one or more times, it is determined that there is a welding abnormality between the pipe member and the joint member, and subsequent processing, for example, processing for stopping the welding work or sounding a buzzer for notifying the welding abnormality, is performed. To do.

When the number of counts by the counting means for determining the welding abnormality is set to one, all the abnormalities can be surely detected, but the error or abnormality of the measuring device itself may be determined as the welding abnormality. is there. Such erroneous detection can be prevented by setting the number of times of counting by the counting means to 2 or more. However, if the number of times of counting is increased too much, it may be judged that a defective product is a good product. Therefore, if the time required for detection is also considered, the number of times is preferably about 2 to 5.

Incidentally, FIG. 4 to FIG. 6 show an example of the result of an experiment conducted by the present inventors to determine the welding abnormality.

FIG. 4 shows a state in which the insertion amount of both ends of the pipe member into the joint member is about half of the insertion amount at the time of proper insertion into the approximate center position (more specifically, the inner diameter is about 6 cm and the length is about 6 cm). About 10c
(A state in which it is inserted approximately 2.4 cm shallower from the center position of the m joint member)
Fig. 5 shows the change in current when the heater is energized. Fig. 5 shows a state in which the insertion amount is made one step shallower than the condition shown in Fig. 4 (specifically, the center of the joint member). When inserted about 2.8 cm shallowly from the position),
The change in current when the heater is energized is shown. In addition, FIG. 6 shows that the insertion amount of the pipe member is an appropriate amount, that is, the fitting member is inserted to a substantially central position and the pushing tip end portion of the pipe member is obliquely cut (specifically, about 18
The graph shows the change in current when the heater is energized in the state of being cut at an angle of °.

As is clear from each data, the current value that surely decreases in the normal state (not shown) tends to increase in the abnormal state. This allows the minimum value of the supply current to be used as a comparison reference value, and a current value that exceeds the allowable range (for example, + 10% of the minimum value) from this value can be judged to be abnormal when measured for a certain period of time. It turns out that

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a schematic block diagram of an electric welding device of the present invention, and FIG. 2 shows a bonding structure of a pipe member and a joint member which are welded by the device.

In FIG. 1, 1 is a coil-shaped heater, 2 is a power supply unit that supplies power to the heater 1 via power supply lines 2a and 2b, and 3 is a current sensor provided in the power supply line 2b. The current sensor 3 detects an output current, converts the output current into a voltage proportional to the current, and outputs the voltage. Further, 4 is an AC / DC converter for converting an AC voltage into a DC voltage proportional to its effective value, 5 is an A / D converter for converting the DC voltage into a digital code that can be read by the microprocessor 6, and 7 is the microprocessor. 6 is a memory for storing the information processed by 6.

That is, the output of the power supply unit 2 that supplies a constant voltage is led to both ends of the heater 1 through the power supply lines 2a and 2b, and the current sensor provided in one of the power supply lines 2b. The output of 3 is led to an AC / DC converter 4 which converts its input into a DC voltage. The output of the AC / DC converter 4 is the A / D converter 5
Is led to the control input of the microprocessor 6. The microprocessor 6 and the memory 7 are bidirectionally connected, and the memory 7 is the A / D converter 5
The information processed based on the input from is appropriately stored, and the microprocessor 6 appropriately reads the information stored in the memory 7. The output of the microprocessor 6 is used as a control signal for the power supply unit 2
Have been led to.

In the electric welding device configured in this manner, the ends of the two pipe members 11, 11 made of a thermoplastic resin such as polyethylene are respectively provided from the both end openings of the joint member 12 made of the same thermoplastic resin to the substantial center. The pipe members 11, 11 and the joint member 12 are inserted and welded to each other by the heat generation action of the heater 1 provided on the inner peripheral surface side of the pipe receiving opening of the joint member 12. The power supply line
Connection terminals 13a, 13b are provided at the tips of 2a, 2b, and the connection terminals 13a, 13b are connected to the voltage application terminals 1a, 1b of the heater 1 formed on the outer peripheral surface of the joint member 12 in a protruding shape. Each is detachably connected.

Next, the operation of the electric welding device having the above structure will be described with reference to the flowchart of FIG.

An electric current is supplied from the power supply unit 2 to the heater 1 through the power supply lines 2a and 2b. Current sensor 3
Detects the supply current at this time, converts it into an AC voltage proportional to the detected current, and outputs it to the AC / DC converter 4. The AC / DC exchanger 4 converts the AC voltage into a DC voltage proportional to its effective value and supplies the DC voltage to the A / D converter 5, and the A / D converter 5 reads the DC voltage by a code that the microprocessor 6 can read. And is supplied to the control input of the microprocessor 6.

In the microprocessor 6, it is checked whether the current value input through the A / D converter 5 is a current value flowing during normal welding or a current value flowing during abnormal welding, and it is determined that the current value is during abnormal welding. When the determination is made, a process of stopping the operation of the power supply unit 2 is performed by sending a control signal indicating the operation stop to the power supply unit 2. Although not shown, processing such as sounding a buzzer for notifying a welding abnormality is performed. Such processing is performed by software in the microphone processor 6.

That is, when the current value input to the microprocessor 6 is the first measured value by the current sensor 3,
It is temporarily stored in the memory 7 as a subsequent comparison reference value.
In this state, when the current value detected by the current sensor 3 next is input to the microprocessor 6 through the AC / DC converter 4 and the / AD converter 5, the microprocessor 6 causes the A / The current value sent from the D converter 5 is once sampled (step), and then the sampled current value is compared with the previous current value stored in the memory 7 (step). And
As a result of the comparison, when the current value measured this time is smaller than the previous current value, the stored content of the memory 7 is updated so that the current measured value is set as the minimum value.
(Step).

On the other hand, in the step, as a result of comparing the current value showing the minimum value stored in the memory 7 with the current value measured by the current sensor 3 thereafter, the current value measured thereafter is stored in the memory 7. When the current value is larger than the current value, the operation moves to the step, and the measured current value is 11 than the current value showing the minimum value stored in the memory 7.
It is determined whether the value is 0% or more, and if it is 110% or more, the value of 1 is incremented. Then, in the next judgment, when the value is 110% or more again, it is incremented by 2 and when the count is 5 or more, it is judged that the welding is abnormal (step), and the step is performed. Move to. Then, when it is determined that there is an abnormality in this way, abnormality processing is performed in step. That is, the microprocessor 6 sends a control signal indicating an operation stop command to the power supply unit 2, stops the operation of the power supply unit 2, and stops the supply of power to the heater 1. Alternatively, although not shown, an alarm buzzer sounds to perform processing such as notifying an operator of a welding abnormality.

By running such an abnormality determination routine once a second, it is possible to determine an abnormality when a current of 110% or more of the minimum value flows for 5 seconds or more.

In addition, in the above embodiment, in order to improve the accuracy of the abnormality determination, the allowable range from the minimum value to + 10% is provided.
This permissible range is not limited to + 10%, but may be + 5% or 0%, for example. Further, in the above-described embodiment, the number of counts is described as 5. However, if it is necessary to strictly determine a welding abnormality according to the purpose of use, the number of counts is set to 1 and a relatively large margin is set. If it is possible to make a decision based on the above, it is possible to set the number of counts to 5 or more.

(Effect of the Invention) As described above, according to the electric welding apparatus of the present invention, the minimum value of the change in current is always stored, and the current value indicating the minimum value is used as a reference to increase the current thereafter. Since it is determined that, regardless of the degree of increase,
It is possible to reliably judge the welding abnormality.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical configuration of an electric welding apparatus of the present invention, FIG. 2 is a view showing a connecting structure between a pipe member and a joint member which are welded by the apparatus, and FIG. Flowcharts for explaining the operation, FIGS. 4 to 6
The drawing is a curve diagram showing the measurement results of the supply current in various poor connection states between the pipe member and the joint member. 1 ... Heating heater, 2 ... Power supply unit 3 ... Current sensor, 4 ... AC / DC converter, 5 ... A / D converter, 6 ... Microprocessor, 7 ... Memory

Claims (1)

[Claims] 1. When joining a pipe member made of a thermoplastic resin and a joint member made of a thermoplastic resin, a heating element is provided on the surface of the joint member in contact with the pipe member, and an electric current is applied to the heating element. In an electric welding device for welding the pipe member and the joint member by supplying, with the current measurement means for measuring the supply current to the heating element, and temporarily storing the first measurement value by the current measurement means, When the current value measured by the current measuring means after a predetermined time is smaller than the temporarily stored previous measured value, the storage content is updated to store the current measured value as the minimum value, and a storage means. The current value showing the minimum value stored in the storage means is compared with the current value measured after a predetermined time, and the current value measured after the predetermined time is recorded. When the current value stored in the means is larger than the minimum current value, a counting means for counting plus 1 is provided, and when the counting means counts up one to a plurality of times, the pipe member and the joint member An electric welding device characterized in that it is judged to be an abnormal welding.