Method and apparatus for controlling resistance welding

• US 4,503,312 A
• Filed: 02/08/1983
• Issued: 03/05/1985
• Est. Priority Date: 06/10/1981
• Status: Expired due to Fees

• Current Assignee: Nippon Avionics Company Limited (NEC Corporation), Nissan Motor Co., Ltd.
• Original Assignee: Nippon Avionics Company Limited (NEC Corporation), Nissan Motor Co., Ltd.
• Inventors: Kawaguchi, Yoshio, Aono, Susumu, Nakata, Shuji
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US06/466,348
• Time in Patent Office: 756 Days
• Field of Search: 219/117.1, 219/110, 219/114, 219/108, 219/86.41
• US Class Current: 219/117.1
• CPC Class Codes: B23K 11/255 the measured parameter being a force B23K11/253 takes precedence

Abstract

Method of controlling resistance welding to obtain high quality welds in which the pressure between the electrodes (2a, 2b) holding the materials (1a, 1b) to be welded is controlled so that the resistance value between the two electrodes (2a, 2b) is a predetermined value, and the welding current is regulated so that the voltage between the electrodes is a predetermined value, and the time during which the welding current flows is controlled to a fixed period.

Claims

1. A method for controlling resistance welding comprising the steps of:

holding the portion of a material to be welded between a pair of electrodes under a pressure;

applying an initial current having a magnitude less than that of a welding current for said electrodes in advance of performing welding;

detecting the resistance between said electrodes in the presence of said initial current;

controlling the pressure on said electrodes on the basis of the detected resistance so as to adjust the resistance between said electrodes to a predetermined resistance;

applying a welding current between said electrodes to perform resistance welding;

detecting the voltage between said electrodes while the welding current is applied thereto;

controlling the welding current flowing between said electrodes to adjust the voltage detected between said electrodes to a predetermined voltage; and

measuring the period during which said welding current is applied and interrupting said welding current when said measured period reaches a predetermined time period.

2. A method for controlling resistance welding comprising the steps of:

holding a welding site of a material to be welded between a pair of electrodes;

applying an initial current smaller than a welding current to perform resistance welding between the electrodes in advance of performing welding;

detecting a resistance value between said electrodes under the presence of the initial current;

controlling the pressure of the electrodes on the basis of the detected resistance value to adjust the resistance value between said electrodes to a predetermined initial resistance value;

applying the welding current between said electrodes;

detecting the resistance value between said electrodes while the welding current is applied;

controlling the pressure in accordance with the resistance value during application of the welding current to maintain the resistance value between said electrodes to a given resistance value having a given relationship to said initial resistance value;

detecting the voltage between said electrodes while the welding current is applied;

controlling the current value to be applied between said electrodes to adjust the voltage detected between said electrodes to a predetermined voltage; and

measuring a time period during which said welding current is applied and interrupting the welding current when the measured time period reaches a predetermined time period.

3. A method for controlling resistance welding comprising the steps of:

holding a welding site of a material to be welded under pressure between a pair of electrodes;

applying an initial current between said electrodes, which initial current has a value smaller than that of a welding current, before applying said welding current;

detecting an initial resistance value between said electrodes with respect to said initial current before applying said welding current;

controlling the pressure between said electrodes to a controlled pressure depending upon the detected initial resistance value to adjust the initial resistance value to a predetermined resistance value;

applying said welding current between said electrodes in the presence of the controlled pressure between said electrodes;

continuously detecting the resistance value between said electrodes while applying said welding current thereto;

continuously controlling said pressure on the basis of the detected resistance value to adjust the resistance value between said electrodes so as to be constantly maintained within a given allowable range with respect to a given resistance value having a given relationship to said predetermined resistance value;

continuously detecting the voltage between said electrodes while applying said welding current during application of the controlled pressure;

controlling the current value applied between said electrodes on the basis of the detected voltage to adjust the voltage so as to be constantly maintained within a given allowable range with respect to a predetermined voltage; and

measuring the time period during which the welding current is applied and interrupting the welding current when the measured time period reaches a predetermined time period.

4. A method for controlling resistance welding comprising the steps of:

pressing a pair of electrodes under pressure onto a welding site of a material to be welded;

applying an initial current having a magnitude smaller than that of a welding current between said electrodes, before applying said welding current;

presetting a predetermined resistance value and a predetermined voltage;

applying said welding current between said electrodes;

detecting the magnitude of said welding current and said initial current at given times;

detecting the voltage between said electrodes at the given time;

arithmetically determining an initial resistance value on the basis of a detected initial current value and the detected voltage and comparing the determined initial resistance value with said predetermined resistance value to obtain the difference therebetween;

adjusting said pressure between said electrodes depending upon the determined difference between said determined and predetermined resistance values so that said difference is maintained smaller than a given value;

comparing the detected voltage with said predetermined voltage to determine a voltage difference;

controlling the welding current to be applied on the basis of the determined voltage difference so as to keep the difference smaller than a given value; and

measuring a period of time during which said welding current is applied and interrupting said welding current when the measured period of time reaches a predetermined period of time.

5. A controlling apparatus for resistance welding comprising:

first means for detecting a first resistance between a pair of welding electrodes by applying an initial current having a value smaller than that of a welding current before supplying the welding current to the welding electrodes, between which members to be welded are pinched, comparing the detected resistance to a predetermined reference resistance to control the pressure between the welding electrodes on the basis of the difference between the detected and predetermined resistances, detecting a second resistance between said welding electrodes while supplying the welding current, and comparing the detected second resistance with a given resistance having a given relationship to said predetermined resistance to control the pressure between said welding electrodes on the basis of the difference of the detected second and given resistances;

second means for detecting the voltage between said welding electrodes while supplying the welding current, comparing the detected voltage with a predetermined reference voltage and controlling the welding current on the basis of the difference between the detected and reference; and

third means for interrupting the welding current when a predetermined current supply time has elapsed to control the period of time for carrying out resistance welding.

8. A controlling system in resistance welding according to any one of claims 5, 6 and 7 which further comprises means (32, 33, 34) for detecting a current supply path on the basis of the resistance between the above welding electrodes and displaying the arrival of replacement timing for the welding electrodes when the free end diameter of the welding electrode indicated by the detected supply path has reached a predetermined free end diameter of the welding electrode.

6. A controlling apparatus for resistance welding which comprises first means for detecting a first resistance between a pair of welding electrodes by supplying an initial current having an amplitude smaller than that of a welding current before the start of supply of welding current to the electrodes between which members to be welded are pinched, comparing the detected first resistance to a predetermined first reference resistance to control the pressure between the welding electrodes in accordance with the difference between said detected and reference first resistances, detecting a second resistance between said welding electrodes while supplying the welding current thereto, and comparing the detected second resistance to a predetermined second reference resistance having a given relationship to said first predetermined reference resistance to control the pressure between the above welding electrodes in accordance with the difference between said detected second resistance and second predetermined reference resistance, means for detecting the voltage between said welding electrodes while supplying the welding current, comparing the detected voltage to a predetermined reference voltage and controlling the welding current in accordance with the difference between said detected and reference voltages, means for interrupting the welding current when a predetermined current supply time has elapsed to control the supply time, and means for detecting the time integral of said detected welding electrode voltage, and interrupting the welding current when the detected integral has reached a predetermined reference integral voltage to control the supply time.

7. A controlling system in resistance welding which comprises:

first means for detecting the resistance between a pair of welding electrodes by supplying an initial current having an amplitude smaller than that of a welding current before supplying of the welding current to the electrodes between which members to be welded are pinched, comparing the detected resistance to a predetermined reference resistance to control the pressure between the welding electrodes on the basis of the difference between the resistances, detecting the resistance between the welding electrodes while supplying the welding current thereto, and comparing the detected resistance with a predetermined reference resistance to control the pressure between the welding electrodes on the basis of the difference between the detected and reference resistances;

second means for detecting the voltage between the welding electrodes while supplying said welding current, comparing the detected voltage with a predetermined reference voltage and controlling the welding current on the basis of the difference between said detected and reference voltage; and

third means for integrating said difference voltage when the detected electrode voltage exceeds a predetermined reference voltage and interrupting the welding current when the integral has reached a predetermined reference integral to control supply time.