US20010054603A1 - Resistance welding power supply apparatus - Google Patents
Resistance welding power supply apparatus Download PDFInfo
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- US20010054603A1 US20010054603A1 US09/884,015 US88401501A US2001054603A1 US 20010054603 A1 US20010054603 A1 US 20010054603A1 US 88401501 A US88401501 A US 88401501A US 2001054603 A1 US2001054603 A1 US 2001054603A1
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- welding
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- switching
- power supply
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/24—Electric supply or control circuits therefor
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K11/00—Resistance welding; Severing by resistance heating
- B23K11/24—Electric supply or control circuits therefor
- B23K11/25—Monitoring devices
- B23K11/252—Monitoring devices using digital means
- B23K11/257—Monitoring devices using digital means the measured parameter being an electrical current
Definitions
- the present invention relates generally to a power supply apparatus for resistance welding, and more particularly, to a power supply apparatus designed to supply a controlled welding current via a switching element to workpieces from a capacitor storing welding energy as electric energy therein.
- Such a resistance welding power supply apparatus has employed switching transistors as the switching element to provide a switching control of the switching transistors by pulse-width modulation (PWM).
- PWM pulse-width modulation
- the PWM is a technique for variably controlling the pulse width of an active level (e.g., high level) within each cycle at every fixed switching cycle defined by a clock.
- the PWM is used to effect a constant-current control allowing the welding current to conform to a set current value so that a switching control can be provided for correcting a deviation of the welding current relative to the set current value for each switching cycle.
- the above transistor-based resistance welding power supply apparatus has often been applied to precision spot welding whose workpieces are mainly precise small-sized metal members such as electronic components.
- desired welding energy must properly be supplied to the workpieces within an extremely brief weld time (e.g., 10 ms or below), which needs a finer and more rapid constant-current control.
- the present invention was conceived in view of the above problem involved in the prior art. It is therefore the object of the present invention to provide a resistance welding power supply apparatus capable of implementing a fine and rapid constant-current control and ensuring an improved resistance welding work quality.
- a resistance welding power supply apparatus having a pair of welding electrodes through which a welding current flows, the pair of welding electrodes adapted to come into pressure contact with workpieces to effect a resistance welding on the workpieces
- the power supply apparatus comprising a capacitor which stores electric energy for resistance welding in the form of electric charges; switching means for the supply of current electrically connected between the capacitor and one electrode of the pair of welding electrodes; and switching control means which, for the purpose of controlling the welding current during the supply of current for resistance welding, provide a control of the switching means such that, if the welding current is less than a set current value at a point of time of monitoring defined to occur at every predetermined time interval, then the switching control means keep the switching means in ON-state from the point of time of monitoring till the time when the welding current exceeds the set current value and that, if the welding current exceeds the set current value at the point of time of monitoring, then the switching control means keep the switching means in OFF-
- the switching element is continuously kept in ON-state from that monitoring point till the time when the welding current exceeds the set current value without being affected by the clock cycle, whereas if the welding current exceeds the set current value at the monitoring point, then the switching element is continuously kept in OFF-state till the next monitoring point.
- Such a switching control allows the switching element to be turned on or off at an unfixed (non-cyclic) timing which is not restrained by the clock cycle to thereby correct (approximately to zero) the deviation or error of the welding current relative to the set current value in a minimum time and realize the rapid and fine constant-current control.
- FIG. 1 is a circuit diagram showing a configuration of a resistance welding power supply apparatus in accordance with an embodiment of the present invention
- FIG. 2 is a flowchart showing a procedure of a welding current control effected in the embodiment
- FIG. 3 illustrates waveforms of currents or signals which may appear at major parts of the embodiment
- FIG. 4 is a circuit diagram showing a configuration of a resistance welding power supply apparatus in accordance with another embodiment of the present invention.
- FIG. 5 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment
- FIG. 6 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment
- FIG. 7 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment.
- FIG. 8 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment.
- the resistance welding power supply apparatus comprises a large-capacitance capacitor 10 for storing resistance welding energy in the form of electric charges, a charging circuit 12 for charging the capacitor 10 to a predetermined voltage, a switching element Q electrically connected between the capacitor 10 and one electrode of a pair of welding electrodes 14 and 16 , and a control unit 20 which allows a switching operation of the switching element Q via a drive circuit 18 during the supply of welding current to provide a control of a welding current I.
- the welding electrodes 14 and 16 are coupled to a pressure mechanism not shown and come into pressure contact with workpieces (W 1 and W 2 ) during the welding work.
- the switching element Q of this embodiment consists of a single or a plurality of switching transistors, e.g., FETs (field effect transistors) TR 1 to TR n which are connected in parallel.
- the switching element Q has a current input terminal connected to a positive electrode of the capacitor 10 and has a current output terminal connected to the welding electrode 14 .
- a freewheeling diode D is connected between the current output terminal of the switching element Q and a negative electrode of the capacitor 10 .
- the control unit 20 is comprised of, e.g., a microprocessor (CPU) or a dedicated logic circuit and, in compliance with a predetermined program or procedure, provides controls of respective parts such as a welding current sequence control, a constant-current control and a capacitor charging control.
- the control unit 20 accepts various set values from an input unit 22 including e.g., a keyboard and accepts a clock signal CK of e.g., 250 kHz for switching control.
- a toroidal coil 26 acting as a current sensor is fitted to a conductor extending between the freewheeling diode D and one of the welding electrodes 14 and 16 so that on the basis of an output signal of the current sensor 26 , a current measuring circuit 28 can feed a current measured value (instantaneous value) MI of the welding current I as an analog signal to the control unit 20 in real time.
- the control unit 20 generates a non-cyclic control pulse CS as will be described later on the basis of the current measured value from the current measuring circuit 28 so as to provide a switching (ON/OFF) control of the switching element Q via the drive circuit 18 by use of the control pulse CS.
- the current measuring circuit 28 may give a digital current measured value MI to the control unit 20 at a higher clock rate than the clock signal CK.
- the charging circuit 12 receives a single-phase AC power supply voltage E of a commercial frequency from an AC power supply line 30 .
- the charging circuit 12 may be comprised of a single-phase rectifying circuit which serves to rectify a single-phase AC voltage from the transformer 32 into a DC voltage.
- a switching circuit for charging may be interposed between an output terminal of the rectifying circuit and the capacitor 10 to provide a finer and variable control of the charging voltage of the capacitor 10 .
- For the charging control there may further be provided voltage measuring means not shown which measure the charging voltage of the capacitor 10 .
- FIG. 2 depicts a procedure of the welding current control provided by the control unit 20 of this embodiment
- FIG. 3 depicts signal or current waveforms which may appear at major parts of this embodiment.
- FIG. 3 further shows as a comparative example a waveform of a control pulse and a waveform of the welding current (I′) in PWM control.
- control unit 20 When the control unit 20 accepts a start signal ST from an external device not shown of a work transfer system for example, it activates a pressure mechanism to allow the welding electrodes 14 and 16 to come into pressure contact with the workpieces (W 1 and W 2 ) by a predetermined pressing force and then executes supplying a welding current.
- the control unit 20 initializes the respective parts of the welding current control system (step A 1 ) and sets various set values (weld time T g , welding current value I s , etc.) of the welding schedules into respective predetermined registers. At this point of time, the switching element Q is left in OFF-state.
- control unit 20 compares a measured value MI of the welding current I acquired from the current measuring circuit 28 with a current set value I s in response to the leading edge of the clock CK (step A 4 ).
- the control unit 20 sets the control pulse CS active, e.g., high (step A 5 )
- the control pulse CS goes high, the switching element Q turns on to allow a DC welding current I to flow through a path or circuit extending from the positive electrode of the capacitor 10 , the switching element Q, the welding electrode 14 , the workpieces (W 1 and W 2 ), the welding electrode 16 and the negative electrode of the capacitor 10 .
- the welding current I is based on discharge of the capacitor 10 and transiently increases with the elapse of time.
- the control unit 20 After setting the control pulse CS high as described above, the control unit 20 continues to monitor the welding current measured value MI from the current measuring circuit 28 without regard to the cycle of the clock CK (steps A 6 ⁇ A 3 ⁇ A 4 ⁇ A 5 ⁇ A 6 ) and, when the welding current measured value MI exceeds the current set value I s , returns the control pulse CS to low (steps A 4 ⁇ A 7 ). Therefore, immediately after the start of the current supplying, the welding current I rises substantially linearly until the welding current I exceeds the set current value I s as depicted in FIG. 3. During this current rise, the control pulse CS remains high without being affected (interrupted) by the cycle of the clock CK. After return of the control pulse CS to low after completion of the rise of the welding current I, the control unit 20 waits for the rise of a subsequently incoming clock CK (steps A 8 ⁇ A 2 ).
- the switching element Q When the control pulse CS goes low, the switching element Q is turned off to bring the discharge of the capacitor 10 to a termination. Then, the welding current I continues to flow through a circuit starting from the welding electrode 14 and passing through the workpieces (W 1 and W 2 ), the welding electrode 16 and the freewheeling diode D and returning to the welding electrode 14 . It is to be understood that the welding current I flowing through the circuit is a freewheeling current generated by the inductance of the load circuit and hence decreases with the elapse of time.
- the control unit 20 Upon receipt of the next clock CK with the control pulse CS being low, the control unit 20 compares the welding current I with the set current value Is at the timing of the leading edge of that clock CK (step A 4 ).
- the control unit 20 keeps the control pulse CS low (step A 7 ) and waits intactly for receipt of the next clock pulse CK (steps A 8 ⁇ A 2 ).
- the welding current I continues to decrease substantially monotonically during at least that clock cycle.
- step A 5 the control pulse CS is set high in the same manner as the above (step A 5 ).
- the control unit 20 continues to increase the welding current I while keeping the control pulse CS high (thereby leaving the switching element Q in ON-state) without regard to the cycle of the clock CK (steps A 6 ⁇ A 3 ⁇ A 4 ⁇ A 5 ⁇ A 6 ).
- the control unit 20 At the time when the welding current I exceeds the set current value I s , the control unit 20 returns the control pulse CS to low to turn off the switching element Q (steps A 4 ⁇ A 7 ). The control unit 20 then waits for receipt of the next clock CK (steps A 8 ⁇ A 2 ).
- the control pulse CS of this embodiment is generated by such a switching control as described above and therefore rises or falls at unfixed timing free from restriction of the cycle of the clock CK.
- a non-cyclic control pulse CS it is possible to accurately cope with deviations or errors of the welding current I relative to the set current value I s , thereby achieving more rapid and finer constant-current control than PWM.
- the deviation can be corrected to substantially null linearly or in the minimum time, whereupon it is possible to provide a stable and secure constant-current control even during the brief weld time in the precision spot welding, etc., and thus to ensure a good finish of weldment.
- FIG. 4 illustrates a configuration of a resistance welding power supply apparatus in accordance with another embodiment of the present invention.
- same reference numerals are given to parts having substantially the same features or functions as the constituent elements of the power supply apparatus of the first embodiment (FIG. 1) described above.
- switching elements Q 1 , Q 2 , Q 3 and Q 4 are connected as seen in FIG. 4 between the capacitor 10 and one of the welding electrodes 14 and 16 .
- the switching elements Q 1 to Q 4 are selectively switching operated to provide a control of the welding current I in a polarity-switchable fashion.
- the switching elements Q 1 to Q 4 may each be comprised of a single or a plurality of switching transistors, e.g., FETs (TR 1 to TR n ) which are connected in parallel.
- the first switching element Q 1 has one terminal electrically connected to the welding electrode 14 and has the other terminal electrically connected to the positive terminal of the capacitor 10 .
- the second switching element Q 2 has one terminal electrically connected to the welding electrode 16 and has the other terminal electrically connected to the negative terminal of the capacitor 10 .
- the third switching element Q 3 has one terminal electrically connected to the welding electrode 16 and has the other terminal electrically connected to the positive terminal of the capacitor 10 .
- the fourth switching element Q 4 has one terminal electrically connected to the welding electrode 14 and has the other terminal electrically connected to the negative terminal of the capacitor 10 .
- diodes D 1 , D 2 , D 3 and D 4 are connected in parallel with the switching elements Q 1 , Q 2 , Q 3 and Q 4 , respectively, to be in an opposite polarities of current to corresponding ones of the switching elements.
- the first to fourth switching elements Q 1 , Q 2 , Q 3 and Q 4 are independently switching (ON/OFF) controlled by first to fourth control pulses CS 1 , CS 2 , CS 3 and CS 4 , respectively, which are given via the drive circuit 18 from the control unit 20 .
- the control unit 20 In a positive current-supplying mode where the welding current I flows through the workpieces (W 1 and W 2 ) in a positive direction, the control unit 20 provides an ON/OFF control of the first and second switching elements Q 1 and Q 2 at a predetermined timing while keeping the third and fourth switching elements Q 3 and Q 4 in OFF-state.
- the first switching element Q 1 may be ON/OFF controlled while keeping the third and fourth switching elements Q 3 and Q 4 in OFF-state but the second switching element Q 2 in ON-state.
- the control unit 20 may generate a control pulse CP 1 for the first switching element Q 1 in the same control procedure as the above embodiment (FIG. 2).
- the third and fourth switching elements Q 3 and Q 4 are ON/OFF controlled at a predetermined timing while keeping the first and second switching elements Q 1 and Q 2 in OFF-state.
- the third switching element Q 3 may be ON/OFF controlled while keeping the first and second switching elements Q 1 and Q 2 in OFF-state but the fourth switching element Q 4 in ON-state.
- the control unit 20 may generate a control pulse CP 3 for the third switching element Q 3 in the same control procedure as the above embodiment (FIG. 2).
- the power supply apparatus of this embodiment is conveniently applied to e.g., two-point simultaneous joining resistance welding (series welding) and makes feasible a high-speed, fine, stable and secure constant-current control with ensured good finish of weldment. Furthermore, effective switching can impart elongated service lives to the elements.
- series welding simultaneous joining resistance welding
Abstract
Description
- 1. Field of the Invention
- The present invention relates generally to a power supply apparatus for resistance welding, and more particularly, to a power supply apparatus designed to supply a controlled welding current via a switching element to workpieces from a capacitor storing welding energy as electric energy therein.
- 2. Description of the Related Arts
- Up until now, such a resistance welding power supply apparatus has employed switching transistors as the switching element to provide a switching control of the switching transistors by pulse-width modulation (PWM).
- The PWM is a technique for variably controlling the pulse width of an active level (e.g., high level) within each cycle at every fixed switching cycle defined by a clock. The PWM is used to effect a constant-current control allowing the welding current to conform to a set current value so that a switching control can be provided for correcting a deviation of the welding current relative to the set current value for each switching cycle.
- The above transistor-based resistance welding power supply apparatus has often been applied to precision spot welding whose workpieces are mainly precise small-sized metal members such as electronic components. In such precision spot welding, desired welding energy must properly be supplied to the workpieces within an extremely brief weld time (e.g., 10 ms or below), which needs a finer and more rapid constant-current control.
- It was however difficult for the conventional transistor-based resistance welding power supply apparatus using PWM to rapidly and finely correct the deviation or error upon the rise of current or upon the unexpected current variation in the constant-current control due to the fact that the switching control is restrained by the
condition 0<Tw<Tc for each switching cycle where Tc is a cycle of the switching cycle and Tw is a pulse width of the control pulse fed to the switching transistors for each switching cycle. - The present invention was conceived in view of the above problem involved in the prior art. It is therefore the object of the present invention to provide a resistance welding power supply apparatus capable of implementing a fine and rapid constant-current control and ensuring an improved resistance welding work quality.
- In order to attain the above object, according to the aspect of the present invention there is provided a resistance welding power supply apparatus having a pair of welding electrodes through which a welding current flows, the pair of welding electrodes adapted to come into pressure contact with workpieces to effect a resistance welding on the workpieces, the power supply apparatus comprising a capacitor which stores electric energy for resistance welding in the form of electric charges; switching means for the supply of current electrically connected between the capacitor and one electrode of the pair of welding electrodes; and switching control means which, for the purpose of controlling the welding current during the supply of current for resistance welding, provide a control of the switching means such that, if the welding current is less than a set current value at a point of time of monitoring defined to occur at every predetermined time interval, then the switching control means keep the switching means in ON-state from the point of time of monitoring till the time when the welding current exceeds the set current value and that, if the welding current exceeds the set current value at the point of time of monitoring, then the switching control means keep the switching means in OFF-state till the next point of time of monitoring.
- In the resistance welding power supply apparatus of the present invention, if the welding current is less than a set current value at a monitoring point defined at predetermined time intervals which is typically given by a clock, then the switching element is continuously kept in ON-state from that monitoring point till the time when the welding current exceeds the set current value without being affected by the clock cycle, whereas if the welding current exceeds the set current value at the monitoring point, then the switching element is continuously kept in OFF-state till the next monitoring point. Such a switching control allows the switching element to be turned on or off at an unfixed (non-cyclic) timing which is not restrained by the clock cycle to thereby correct (approximately to zero) the deviation or error of the welding current relative to the set current value in a minimum time and realize the rapid and fine constant-current control.
- The above and other objects, aspects, features and advantages of the present invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings, in which:
- FIG. 1 is a circuit diagram showing a configuration of a resistance welding power supply apparatus in accordance with an embodiment of the present invention;
- FIG. 2 is a flowchart showing a procedure of a welding current control effected in the embodiment;
- FIG. 3 illustrates waveforms of currents or signals which may appear at major parts of the embodiment;
- FIG. 4 is a circuit diagram showing a configuration of a resistance welding power supply apparatus in accordance with another embodiment of the present invention;
- FIG. 5 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment;
- FIG. 6 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment;
- FIG. 7 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment; and
- FIG. 8 illustrates a current-supplying circuit through which a welding current flows in one switching state in the power supply apparatus of the embodiment.
- The present invention will now be described with reference to the accompanying drawings which illustrate a preferred embodiment thereof in a non-limitative manner.
- Referring first to FIG. 1 there is depicted a configuration of a resistance welding power supply apparatus in accordance with the embodiment of the present invention. The resistance welding power supply apparatus comprises a large-
capacitance capacitor 10 for storing resistance welding energy in the form of electric charges, acharging circuit 12 for charging thecapacitor 10 to a predetermined voltage, a switching element Q electrically connected between thecapacitor 10 and one electrode of a pair ofwelding electrodes control unit 20 which allows a switching operation of the switching element Q via adrive circuit 18 during the supply of welding current to provide a control of a welding current I. Thewelding electrodes - The switching element Q of this embodiment consists of a single or a plurality of switching transistors, e.g., FETs (field effect transistors) TR1 to TRn which are connected in parallel. The switching element Q has a current input terminal connected to a positive electrode of the
capacitor 10 and has a current output terminal connected to thewelding electrode 14. A freewheeling diode D is connected between the current output terminal of the switching element Q and a negative electrode of thecapacitor 10. - The
control unit 20 is comprised of, e.g., a microprocessor (CPU) or a dedicated logic circuit and, in compliance with a predetermined program or procedure, provides controls of respective parts such as a welding current sequence control, a constant-current control and a capacitor charging control. Thecontrol unit 20 accepts various set values from aninput unit 22 including e.g., a keyboard and accepts a clock signal CK of e.g., 250 kHz for switching control. - For measurement or feedback of the welding current I in the constant-current control, a
toroidal coil 26 acting as a current sensor is fitted to a conductor extending between the freewheeling diode D and one of thewelding electrodes current sensor 26, acurrent measuring circuit 28 can feed a current measured value (instantaneous value) MI of the welding current I as an analog signal to thecontrol unit 20 in real time. Thecontrol unit 20 generates a non-cyclic control pulse CS as will be described later on the basis of the current measured value from thecurrent measuring circuit 28 so as to provide a switching (ON/OFF) control of the switching element Q via thedrive circuit 18 by use of the control pulse CS. It is to be noted that thecurrent measuring circuit 28 may give a digital current measured value MI to thecontrol unit 20 at a higher clock rate than the clock signal CK. - Via a step-
down transformer 32, thecharging circuit 12 receives a single-phase AC power supply voltage E of a commercial frequency from an ACpower supply line 30. Thecharging circuit 12 may be comprised of a single-phase rectifying circuit which serves to rectify a single-phase AC voltage from thetransformer 32 into a DC voltage. A switching circuit for charging may be interposed between an output terminal of the rectifying circuit and thecapacitor 10 to provide a finer and variable control of the charging voltage of thecapacitor 10. For the charging control there may further be provided voltage measuring means not shown which measure the charging voltage of thecapacitor 10. - FIG. 2 depicts a procedure of the welding current control provided by the
control unit 20 of this embodiment, and FIG. 3 depicts signal or current waveforms which may appear at major parts of this embodiment. FIG. 3 further shows as a comparative example a waveform of a control pulse and a waveform of the welding current (I′) in PWM control. - When the
control unit 20 accepts a start signal ST from an external device not shown of a work transfer system for example, it activates a pressure mechanism to allow thewelding electrodes - First, the
control unit 20 initializes the respective parts of the welding current control system (step A1) and sets various set values (weld time Tg, welding current value Is, etc.) of the welding schedules into respective predetermined registers. At this point of time, the switching element Q is left in OFF-state. - Then, upon receipt of a clock CK (step A2), the
control unit 20 compares a measured value MI of the welding current I acquired from thecurrent measuring circuit 28 with a current set value Is in response to the leading edge of the clock CK (step A4). - When the current measured value MI is smaller than the current set value Is (MI<Is) in this comparison, the
control unit 20 sets the control pulse CS active, e.g., high (step A5) When the control pulse CS goes high, the switching element Q turns on to allow a DC welding current I to flow through a path or circuit extending from the positive electrode of thecapacitor 10, the switching element Q, thewelding electrode 14, the workpieces (W1 and W2), thewelding electrode 16 and the negative electrode of thecapacitor 10. The welding current I is based on discharge of thecapacitor 10 and transiently increases with the elapse of time. - After setting the control pulse CS high as described above, the
control unit 20 continues to monitor the welding current measured value MI from thecurrent measuring circuit 28 without regard to the cycle of the clock CK (steps A6→A3→A4→A5→A6) and, when the welding current measured value MI exceeds the current set value Is, returns the control pulse CS to low (steps A4→A7). Therefore, immediately after the start of the current supplying, the welding current I rises substantially linearly until the welding current I exceeds the set current value Is as depicted in FIG. 3. During this current rise, the control pulse CS remains high without being affected (interrupted) by the cycle of the clock CK. After return of the control pulse CS to low after completion of the rise of the welding current I, thecontrol unit 20 waits for the rise of a subsequently incoming clock CK (steps A8→A2). - When the control pulse CS goes low, the switching element Q is turned off to bring the discharge of the
capacitor 10 to a termination. Then, the welding current I continues to flow through a circuit starting from thewelding electrode 14 and passing through the workpieces (W1 and W2), thewelding electrode 16 and the freewheeling diode D and returning to thewelding electrode 14. It is to be understood that the welding current I flowing through the circuit is a freewheeling current generated by the inductance of the load circuit and hence decreases with the elapse of time. - Upon receipt of the next clock CK with the control pulse CS being low, the
control unit 20 compares the welding current I with the set current value Is at the timing of the leading edge of that clock CK (step A4). - Provided that the current measured value MI exceeds the current set value Is in this comparison (MI>Is), the
control unit 20 keeps the control pulse CS low (step A7) and waits intactly for receipt of the next clock pulse CK (steps A8→A2). Thus, the welding current I continues to decrease substantially monotonically during at least that clock cycle. - On the contrary, if the current measured value MI is less than the current set value Is (MI<Is), then the control pulse CS is set high in the same manner as the above (step A5). This allows the switching element Q to turn on at the timing of the leading edge of the clock CK in that clock cycle, with the result that the welding current I increases in turn. The
control unit 20 continues to increase the welding current I while keeping the control pulse CS high (thereby leaving the switching element Q in ON-state) without regard to the cycle of the clock CK (steps A6→A3→A4→A5→A6). At the time when the welding current I exceeds the set current value Is, thecontrol unit 20 returns the control pulse CS to low to turn off the switching element Q (steps A4→A7). Thecontrol unit 20 then waits for receipt of the next clock CK (steps A8→A2). - In the constant-current control of this embodiment, in this manner, if the welding current I is less than the set current value Is at a point of time on the leading edge of the clock CK, then the control pulse CS for the switching element Q is held active or high, without being influenced by the cycle of the clock CK, from that point of time till the time when the welding current I exceeds the set current value Is, whereas if the welding current I exceeds the set current value Is at the leading edge of the clock CK, then the control pulse CS is held inactive or low till the leading edge of the next clock CK.
- As seen in FIG. 3, the control pulse CS of this embodiment is generated by such a switching control as described above and therefore rises or falls at unfixed timing free from restriction of the cycle of the clock CK. However, by virtue of such a non-cyclic control pulse CS, it is possible to accurately cope with deviations or errors of the welding current I relative to the set current value Is, thereby achieving more rapid and finer constant-current control than PWM. In particular, where a large deviation is present e.g., immediately after the start of the current supplying or due to the sharp impedance variations of the workpieces (W1 and W2), the deviation can be corrected to substantially null linearly or in the minimum time, whereupon it is possible to provide a stable and secure constant-current control even during the brief weld time in the precision spot welding, etc., and thus to ensure a good finish of weldment.
- Reference is then made to FIG. 4 which illustrates a configuration of a resistance welding power supply apparatus in accordance with another embodiment of the present invention. In the diagram, same reference numerals are given to parts having substantially the same features or functions as the constituent elements of the power supply apparatus of the first embodiment (FIG. 1) described above.
- In the resistance welding power supply apparatus of this embodiment, four switching elements Q1, Q2, Q3 and Q4 are connected as seen in FIG. 4 between the
capacitor 10 and one of thewelding electrodes - The first switching element Q1 has one terminal electrically connected to the
welding electrode 14 and has the other terminal electrically connected to the positive terminal of thecapacitor 10. The second switching element Q2 has one terminal electrically connected to thewelding electrode 16 and has the other terminal electrically connected to the negative terminal of thecapacitor 10. The third switching element Q3 has one terminal electrically connected to thewelding electrode 16 and has the other terminal electrically connected to the positive terminal of thecapacitor 10. The fourth switching element Q4 has one terminal electrically connected to thewelding electrode 14 and has the other terminal electrically connected to the negative terminal of thecapacitor 10. In parallel with the switching elements Q1, Q2, Q3 and Q4 are connected diodes D1, D2, D3 and D4, respectively, to be in an opposite polarities of current to corresponding ones of the switching elements. - The first to fourth switching elements Q1, Q2, Q3 and Q4 are independently switching (ON/OFF) controlled by first to fourth control pulses CS1, CS2, CS3 and CS4, respectively, which are given via the
drive circuit 18 from thecontrol unit 20. - In a positive current-supplying mode where the welding current I flows through the workpieces (W1 and W2) in a positive direction, the
control unit 20 provides an ON/OFF control of the first and second switching elements Q1 and Q2 at a predetermined timing while keeping the third and fourth switching elements Q3 and Q4 in OFF-state. - For example, as seen in FIGS. 5 and 6, for the duration of the positive current-supplying mode, the first switching element Q1 may be ON/OFF controlled while keeping the third and fourth switching elements Q3 and Q4 in OFF-state but the second switching element Q2 in ON-state. In such a case, the
control unit 20 may generate a control pulse CP1 for the first switching element Q1 in the same control procedure as the above embodiment (FIG. 2). - In a negative current-supplying mode where the welding current I flows through the workpieces (W1 and W2) in a negative direction, the third and fourth switching elements Q3 and Q4 are ON/OFF controlled at a predetermined timing while keeping the first and second switching elements Q1 and Q2 in OFF-state.
- For example, as seen in FIGS. 7 and 8, for the duration of the negative current-supplying mode, the third switching element Q3 may be ON/OFF controlled while keeping the first and second switching elements Q1 and Q2 in OFF-state but the fourth switching element Q4 in ON-state. In this case as well, the
control unit 20 may generate a control pulse CP3 for the third switching element Q3 in the same control procedure as the above embodiment (FIG. 2). - The power supply apparatus of this embodiment is conveniently applied to e.g., two-point simultaneous joining resistance welding (series welding) and makes feasible a high-speed, fine, stable and secure constant-current control with ensured good finish of weldment. Furthermore, effective switching can impart elongated service lives to the elements.
- According to the resistance welding power supply apparatus of the present invention, as set forth hereinabove, it is possible to implement a fine and high-speed constant-current control and to improve the work quality of the resistance welding.
- While illustrative and presently preferred embodiments of the present invention have been described in detail herein, it is to be understood that the inventive concepts may be otherwise variously embodied and employed and that the appended claims are intended to be construed to include such variations except insofar as limited by the prior art.
Claims (4)
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP2000-189506 | 2000-06-23 | ||
JP2000189506A JP4420537B2 (en) | 2000-06-23 | 2000-06-23 | Resistance welding power supply |
Publications (2)
Publication Number | Publication Date |
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US20010054603A1 true US20010054603A1 (en) | 2001-12-27 |
US6455802B2 US6455802B2 (en) | 2002-09-24 |
Family
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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US09/884,015 Expired - Fee Related US6455802B2 (en) | 2000-06-23 | 2001-06-20 | Resistance welding power supply apparatus |
Country Status (5)
Country | Link |
---|---|
US (1) | US6455802B2 (en) |
EP (1) | EP1166944A3 (en) |
JP (1) | JP4420537B2 (en) |
KR (1) | KR100727378B1 (en) |
CN (1) | CN1330995A (en) |
Cited By (2)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110168684A1 (en) * | 2010-01-13 | 2011-07-14 | Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. | Weld current generating apparatus |
US20140076860A1 (en) * | 2012-09-13 | 2014-03-20 | Bob Morrow | Sensing Apparatus for Resistance Welding and Related Method |
Families Citing this family (6)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US7307236B2 (en) * | 2005-12-02 | 2007-12-11 | Image Industries, Inc. | Charge and weld gating system with safety circuit |
DE102006035147A1 (en) * | 2006-05-03 | 2007-11-15 | Lupotron Gmbh | Welding process and welding equipment |
EP2400358B1 (en) | 2010-06-24 | 2016-03-30 | Borealis AG | Iterative production process control |
JP5733854B2 (en) * | 2010-09-08 | 2015-06-10 | 日本アビオニクス株式会社 | Welding power source |
JP2014061535A (en) * | 2012-09-21 | 2014-04-10 | Takeshi Morita | Portable spot welder |
JP2018011121A (en) * | 2016-07-11 | 2018-01-18 | 株式会社ダイヘン | Communication system and welding system |
Family Cites Families (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPS6137383A (en) * | 1984-07-28 | 1986-02-22 | Mitsubishi Electric Corp | Power source device for welding |
US5149933A (en) * | 1991-12-20 | 1992-09-22 | Hughes Aircraft Company | Welding control |
US5748462A (en) * | 1995-08-02 | 1998-05-05 | Miyachi Technos Corporation | Apparatus for controlling inverter resistance welding |
JPH11129077A (en) * | 1997-10-29 | 1999-05-18 | Miyachi Technos Corp | Resistant welding power source device |
JP2000052051A (en) * | 1998-08-10 | 2000-02-22 | Miyachi Technos Corp | Inverter type resistance welding control device |
-
2000
- 2000-06-23 JP JP2000189506A patent/JP4420537B2/en not_active Expired - Fee Related
-
2001
- 2001-06-12 KR KR1020010032912A patent/KR100727378B1/en active IP Right Grant
- 2001-06-18 EP EP01305288A patent/EP1166944A3/en not_active Withdrawn
- 2001-06-20 US US09/884,015 patent/US6455802B2/en not_active Expired - Fee Related
- 2001-06-23 CN CN01124336A patent/CN1330995A/en active Pending
Cited By (3)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
US20110168684A1 (en) * | 2010-01-13 | 2011-07-14 | Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. | Weld current generating apparatus |
US8269142B2 (en) * | 2010-01-13 | 2012-09-18 | Hong Fu Jin Precision Industry (Shenzhen) Co., Ltd. | Weld current generating apparatus |
US20140076860A1 (en) * | 2012-09-13 | 2014-03-20 | Bob Morrow | Sensing Apparatus for Resistance Welding and Related Method |
Also Published As
Publication number | Publication date |
---|---|
JP4420537B2 (en) | 2010-02-24 |
EP1166944A3 (en) | 2003-05-07 |
EP1166944A2 (en) | 2002-01-02 |
JP2002001544A (en) | 2002-01-08 |
KR20020001529A (en) | 2002-01-09 |
KR100727378B1 (en) | 2007-06-12 |
US6455802B2 (en) | 2002-09-24 |
CN1330995A (en) | 2002-01-16 |
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