Spot welding apparatus

• US 5,484,975 A
• Filed: 07/15/1994
• Issued: 01/16/1996
• Est. Priority Date: 07/22/1993
• Status: Expired due to Term

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Itatsu, Makoto
• Primary Examiner(s): Shaw, Clifford C.
• Application Number:
  US08/272,988
• Time in Patent Office: 550 Days
• Field of Search: 219/86.51, 219/110, 219/117.1, 219/86.25, 219/86.7
• US Class Current: 219/86.7
• CPC Class Codes: B23K 11/115 by means of two electrodes placed opposite one another on both sides of the welded parts
• CPC Class Codes: B23K 11/24 Electric supply or control circuits therefor

Abstract

A spot welding apparatus comprises a welding gun having a pair of opposing welding electrodes either one of which is movable towards the other to apply a pressure onto a work and away from the other to release the pressure, a servomotor attached to the welding gun for adjusting the pressure applied to the work through movement of the movable welding electrode, a servomotor controller for controlling an operation of the servomotor, a welding current regulator for adjusting a value of welding current applied through the opposing electrodes to the work, a weld-interval timer arranged for adjusting at least one weld time interval and weld timing for the welding current and the pressure both applied to the work, and a spot welding controller electronically connected to the servomotor controller, the welding current regulator and the weld-interval timer, for simultaneously and arbitrarily adjusting a welding condition, namely the welding current, the pressure, the weld time interval and the weld timing, during a cycle of spot welding at every welding point on the work or at one specified welding point on the work.

Claims

1. A spot welding apparatus comprising:

a welding gun having a pair of opposing welding electrodes either one of which is movable towards the other to apply a pressure onto a work and away from the other to release the pressure;

a servomotor attached to said welding gun for adjusting the pressure applied to the work through movement of said movable welding electrode;

a servomotor controller for controlling an operation of said servomotor;

a welding current regulator for adjusting a value of welding current applied through the opposing electrodes to the work;

a weld-interval timer arranged for adjusting at least one weld time interval and weld timing for said welding current and said pressure both applied to the work; and

a spot welding controller electronically connected to said servomotor controller, said welding current regulator and said weld-interval timer, for simultaneously and arbitrarily adjusting the welding current, the pressure, the weld time interval and the weld timing, based on teaching data, during one cycle of spot welding at one specified welding point on the work.

2. A spot welding apparatus comprising:

a welding gun having a pair of opposing welding electrodes either one of which is movable towards the other to apply a pressure onto a work and away from the other to release the pressure;

a servomotor attached to said welding gun for adjusting the pressure applied to the work through movement of said movable welding electrode;

a servomotor controller for adjusting a rotational movement of said servomotor to produce the movement of said movable welding electrode;

a welding current regulator for adjusting a value of welding current applied through the opposing electrodes to the work;

a weld-interval timer arranged for adjusting at least one weld time interval and weld timing for said welding current and said pressure both applied to the work; and

a spot welding controller electronically connected to said servomotor controller, said welding current regulator and said weld-interval timer, for simultaneously and arbitrarily adjusting the welding current, the pressure, the weld time interval and the weld timing, based on teaching data,

wherein said spot welding controller includes means for providing a given welding mode for one specified welding point on the work, in which (a) a first pressure having a given pressure level and a first welding current having a given low current value are applied to the work for a first period of weld time, (b) a second pressure having a higher pressure level than said first pressure and a second welding current which current increases in proportion to an elapsed time after said first period has elapsed, are applied to the work for a second period of weld time, (c) a third pressure having a predetermined medium pressure level midway between said first and second pressures and a third welding current having a given high current value are applied to the work for a third period of weld time, (d) a fourth pressure having a higher pressure level than said third pressure and a fourth welding current which current decreases in proportion to an elapsed time after said third period has elapsed, are applied to the work for a fourth period of weld time, and (e) a fifth pressure having a given lower pressure level than said third pressure and a fifth welding current having a given low current value are applied to the work for a fifth period of weld time, and said first to fifth periods are arrayed in that order.

3. A spot welding apparatus, comprising:

a welding gun having a pair of opposing welding electrodes either one of which is movable towards the other to apply a pressure onto a work and away from the other to release the pressure;

a servomotor attached to said welding gun for adjusting the pressure applied to the work through movement of said movable welding electrode;

a servomotor controller for adjusting a rotational movement of said servomotor through a numerical control to produce the movement of said movable welding electrode;

a welding transformer for adjusting a value of welding current applied through the opposing electrodes to the work;

a weld-interval timer arranged for adjusting at least one weld time interval and weld timing for said welding current and said pressure both applied to the work; and

a spot welding controller electronically connected to said servomotor controller, said welding transformer and said weld-interval timer, for simultaneously and arbitrarily adjusting the welding current, the pressure, the weld time interval and the weld timing, based on teaching data,

wherein said spot welding controller includes a spatter-loss reduction means for reducing spatter loss by stepping up the pressure applied to the work to a greater pressure level than a predetermined medium pressure applied to the work for a predetermined intermediate weld time interval, for a predetermined first time period shorter than the predetermined intermediate weld time interval just after starting to apply the welding current and for a predetermined second time period shorter than the predetermined intermediate weld time interval just before terminating to apply the welding current, during one cycle of spot welding at one specified welding point on the work.

4. A spot welding apparatus as recited in claim 3, wherein said spot welding controller operates for simultaneously and arbitrarily adjusting the welding current, the pressure, the weld time interval and the weld timing based on the teaching data during one cycle of spot welding at one specified welding point on the work.

5. A spot welding apparatus comprising:

a welding gun having a pair of opposing welding electrodes either one of which is movable towards the other to apply a pressure onto a work and away from the other to release the pressure;

a servomotor attached to said welding gun for adjusting the pressure applied to the work through movement of said movable welding electrode;

a servomotor controller for controlling an operation of said servomotor;

a welding current regulator for adjusting a value of welding current applied through the opposing electrodes to the work;

a weld-interval timer arranged for adjusting at least one weld time interval and weld timing for said welding current and said pressure both applied to the work; and

a spot welding controller electronically connected to said servomotor controller, said welding current regulator and said weld-interval timer, for simultaneously and arbitrarily adjusting the welding current, the pressure, the weld time interval and the weld timing, based on teaching data, during one cycle of spot welding at one specified welding point on the work, so that the pressure is stepped up and down to a plurality of pressure levels and that the welding current is linearly increased for a predetermined short time duration after initiation of application of the welding current and is held constant at a predetermined current level for a predetermined time duration after reaching the predetermined current level, and is then decreased linearly to zero for a predetermined short time duration until termination of application of the welding current.