JP2001025880A5 - - Google Patents

Claims (25)

In a spot welding apparatus in which a material to be welded is pressed with an electrode tip attached to each opposing clamping part and welded by resistance heating, welding vibration detecting means for detecting vibration of the electrode tip during welding, and welding vibration detecting means A welding quality determining means for judging whether or not the detected welding vibration waveform is a welding vibration pattern satisfying a predetermined design value of welding strength , wherein the welding vibration detecting means is a non-consumable pressurizing member in the vicinity of the electrode tip It is attached to the spot welding apparatus characterized by the above-mentioned.   The spot welding apparatus according to claim 1, wherein the welding quality determination means performs quality determination of the welding state based on the amplitude level of the welding vibration waveform detected by the welding vibration detection means.   The spot welding apparatus according to claim 1, wherein the welding quality determination unit performs the quality determination of the welding state based on a temporal change pattern of an envelope of the welding vibration waveform detected by the welding vibration detection unit.   The spot welding apparatus according to claim 1, wherein the welding quality determination unit performs the quality determination of the welding state based on a temporal change in the frequency distribution of the welding vibration waveform detected by the welding vibration detection unit.   The spot welding apparatus according to claim 1, wherein the welding quality determination unit performs the quality determination of the welding state based on the natural vibration frequency of the material point of the pressing side clamping portion detected by the welding vibration detection unit.   Welding control means for controlling at least one of welding current, energizing time, and applied pressure to the electrode tip is provided, the welding pass / fail judgment means detects the amplitude level of the welding vibration waveform detected by the welding vibration detection means, welding vibration A welding state based on at least one of a time variation pattern of a waveform envelope, a time variation of a frequency distribution of a welding vibration waveform, a natural vibration frequency of a material point of a pressing side holding portion, and a time series change of the natural vibration frequency The spot welding apparatus according to claim 1, wherein at least one of welding current, energization time, and pressurizing force by the welding control means is feedback-controlled based on the determination result.   The electrode tip shaping / replacement determining means includes the electrode tip shaping / replacement determining means, and the electrode tip shaping / replacement determining means determines whether the natural vibration frequency of the material point of the pressing side holding portion reaches the predetermined frequency from the start of welding current application. The spot welding apparatus according to claim 5 or 6, wherein the time for shaping or replacement is determined.   2. The welding quality determination unit according to claim 1, wherein the welding quality determination unit performs the quality determination of the welding state based on a result obtained by integrating the envelope of the welding vibration waveform detected by the welding vibration detection unit within a predetermined period. Spot welding equipment.   The welding quality determination means performs quality determination of the welding state based on a result of definite integration within a predetermined period of an envelope of the natural vibration frequency or higher-order vibration frequency of the mass point of the pressing side clamping portion. Item 10. The spot welding apparatus according to Item 1.   The spot welding apparatus according to claim 8 or 9, wherein the definite integration period is between the nugget formation start time and the nugget growth saturation time.   A time counter that measures the time from the welding current energization start time to the amplitude expansion start time of the welding vibration waveform detected by the welding vibration detection means; and the welding pass / fail judgment means at the time measured by the time counter. The spot welding apparatus according to claim 1, wherein the quality of the welding state is determined based on the determination.   The electrode tip shaping / replacement determining means is provided, wherein the electrode tip shaping / replacement determining means determines the shaping or replacement time of the electrode tip based on the time measured by the time counter. The spot welding apparatus as described.   A time counter that measures the time from the welding current energization start time to the amplitude expansion start time of the welding vibration waveform detected by the welding vibration detection means, and a means for calculating the current amount of the welding current energized within the time 2. The spot welding apparatus according to claim 1, wherein the welding quality determination means performs quality determination of the welding state based on the amount of current.   The welding pass / fail judgment means performs the pass / fail judgment of the welding state when at least one of a signal indicating energization of the welding current to the electrode tip or a signal indicating pressurization to the electrode tip is valid. The spot welding apparatus according to claim 1, wherein   A welding current stop instruction circuit for outputting a welding current energization stop command is provided, and the circuit detects the welding current after a predetermined time has elapsed from the amplitude expansion start time or amplitude saturation time of the welding vibration waveform detected by the welding vibration detection means. The spot welding apparatus according to claim 1, wherein energization is stopped.   The spot welding apparatus according to any one of claims 1 to 15, wherein the welding vibration detection means includes an acceleration sensor that detects acceleration of the electrode tip during welding.   The spot welding apparatus according to any one of claims 1 to 15, wherein the welding vibration detection means includes a displacement sensor that detects displacement of the electrode tip during welding.   The spot welding apparatus according to any one of claims 1 to 15, wherein the welding vibration detecting means includes a pressure sensor that detects a pressure applied to the electrode tip during welding.   The spot welding apparatus according to any one of claims 1 to 15, wherein the welding vibration detection means includes a strain gauge for detecting strain between the electrode tip and the pressure source during welding.   16. The welding vibration detecting means includes two acceleration sensors for detecting acceleration of each electrode tip, and detects vibration during welding from a difference between outputs of both acceleration sensors. The spot welding apparatus in any one.   The spot welding apparatus according to any one of claims 1 to 15, wherein the welding vibration detecting means includes a vibration sensor that detects an electrode tip vibration frequency during welding.   The spot welding apparatus according to claim 1, wherein the welding vibration detection means includes a resonance mechanism that resonates with a detection target frequency.   23. The spot welding apparatus according to claim 22, wherein the welding vibration detection means includes a resonance frequency variable mechanism that can change a resonance frequency.   The spot welding apparatus according to any one of claims 16, 21 and 22, wherein the sensitivity axis of the welding vibration detecting means is aligned with an in-plane direction of a current loop plane formed by an energization path for welding current.   The spot welding apparatus according to any one of claims 1 to 15, wherein a welding vibration detecting means is attached to the grounded electrode side in the spot welding apparatus in which the secondary circuit of the welding current is grounded.