JP4786142B2 - Construction machinery - Google Patents

Description

  The present invention relates to a construction machine provided with a three-phase AC motor that is supplied with a three-phase AC via a cable member and is repeatedly operated or stopped.

  In the foundation work performed at the construction site, a hole excavation work is performed in order to embed the pile deep underground, and a construction machine equipped with a hole excavator called an “auger” is used for this hole excavation work (for example, Patent Document 1). And as a drive means of this auger, it is normal to use the three-phase alternating current motor from which a big driving force and high efficiency are obtained.

  FIG. 6 is an explanatory diagram showing the configuration of the entire conventional construction machine used by the present applicant, although it is not exactly the same as that according to Patent Document 1. A support member 62 called “catch hawk” is attached to the front of the base machine 61 on which the driver is boarded, and a backstay 63 is attached to the rear. The lower part of the leader 64 serving as a pillar member of the hole excavator is supported by the support member 62 and the upper part is supported by the backstay 63. At this time, the lower surfaces of the reader 64 and the backstay 63 are fixed on the ground 67 via the support legs 65 and 66, respectively, and the base machine 61 and the reader 64 maintain a stable posture as a whole. I'm leaning.

  A guide rail 68 is disposed on the side surface of the leader 64, and an excavation mechanism 69 is attached so that the guide rail 68 can be moved up and down along the guide rail 68. The excavation mechanism 69 includes a three-phase AC motor 70 and a speed reducer 71 attached to the rotation shaft of the three-phase AC motor 70 (the arrangement state of the three-phase AC motor 70 and the speed reducer 71 is illustrated in the drawing. For the sake of convenience, the illustration is different from the actual state.)

  An auger screw 72 is fixed to the speed reducer 71, and a head 73 is attached to the tip of the auger screw 72. In addition, a lower swing-preventing member 74 and an intermediate swing-preventing member 75 for preventing the auger screw 72 from swinging over a certain range are provided near the lower end portion and the intermediate portion of the reader 64, respectively. Although only one auger screw 72 is visible in the direction shown in FIG. 6, this hole excavator is of a multi-axis type, and when viewed from the front direction, that is, the right direction in FIG. Usually, about 3 to 5 auger screws 72 are arranged in parallel.

  A suspended sheave block 76 is attached to the upper portion of the excavating mechanism 69, and a top sheave mechanism 77 having a sheave 78 is disposed on the upper portion of the leader 64. The other end side of the wire member 79 that is attached to the base machine 61 at one end side is attached to the hanging sheave block 76. That is, the excavation mechanism 69 and the auger screw 72 are suspended by the wire member 79, and descend along the guide rail 68 as the hole excavation work proceeds.

  Inside the base machine 61, there is provided an operation panel 80 for operation by an operator, and a control panel 81 in which various electric circuit components and the like are disposed at the rear position. . A cabtire cable 82 extending from the control panel 81 is connected to the three-phase AC motor 70 of the excavation mechanism 69.

  In FIG. 6, the excavating mechanism 69 has a type having the speed reducer 71, but there is a type having no speed reducer 71. In the case of this type, the auger screw 72 is directly driven to rotate by the three-phase AC motor 70.

  Next, the operation of FIG. 6 will be described. When the operator presses the operation switch in the operation panel 80 to start the hole excavation work, the operation control signal S1 is input to the control circuit in the control panel 81, and thereby the excavation mechanism is connected via the cabtyre cable 82. Three-phase AC power is supplied to the three-phase AC motor 70 of 69, and the three-phase AC motor 70 rotates in the forward rotation direction. At the same time, the excavating mechanism 69 and the auger screw 72 suspended by the wire member 79 start to descend, and eventually the head 73 reaches the ground 67 and the hole excavation is started.

  The auger screw 72 that rotates in the forward direction still descends while the mud excavated by the head 73 is spirally discharged upward. When the operator confirms that excavation has been performed to a certain depth, the operator stops the rotation of the three-phase AC motor 70 and then raises the auger screw 72 and the excavation mechanism 69 while rotating in the reverse direction. To. Then, the rotation of the three-phase AC motor 70 is stopped in a state where the head 73 is pulled out from the ground 67, and the hole excavation work is ended.

Here, at the construction site, the soil quality and hardness of the excavation site are usually not uniform, and obstacles often appear during excavation work. Usually, the rotation / reverse rotation or operation / stop is repeated frequently.
JP 2003-13447 A

  By the way, the supply of the three-phase AC power to the three-phase AC motor 70 is performed from the control panel 81 via the cabtyre cable 82, and the connection work of the cabtire cable 82 is performed at the construction site. . As long as the cabtyre cable 82 is correctly connected, no particular problem occurs. However, sometimes the connection is wrong and the three-phase AC motor 70 may be operated in a single phase (that is, a phase loss operation) with one of the three phases missing. In addition, although the cabtyre cable 82 was initially correctly connected, the cabtyre cable 82 is caught by an obstacle when the excavating mechanism 69 moves up and down during the hole excavation work, or during the work. Due to the vibration, the cable of any phase may be disconnected or disconnected, and the phase loss operation may be performed halfway.

  In addition, operating the three-phase AC motor in a phase-down manner means operating the three-phase AC motor in an overload state. The three-phase AC motor 70 is usually provided with a thermal relay, and overload protection is provided for the time being by the action of this thermal relay, so that the motor windings are prevented from being burned out (however, the motor Depending on the operating conditions, it may take time to detect the overload, and as a result, a long overload operation may be performed and the windings may be burnt out.)

  Here, as described above, the excavation mechanism 69 includes a type having the reduction gear 71 as shown in FIG. 6 and a type not having the reduction gear 71. When a phase-opening operation is performed, the above-described thermal relay overload protection function can be used for either the former or the latter type as soon as the phase-opening operation is noticed and the normal three-phase operation is immediately restored. Therefore, it is possible to prevent the motor windings from being burned out.

  However, in the case of the former type, if the phase loss operation is performed even for a short time and an overload condition occurs, the speed reducer 71 is damaged. When such a situation occurs, the construction company carrying out the construction work has to suspend the hole excavation work, greatly affecting the work schedule and at the same time putting a considerable economic burden on the repair of the reducer 71. The result will be forced.

  Therefore, in the construction machine equipped with the former type of excavation mechanism, it is required for the field worker to pay sufficient attention so as not to perform the phase loss operation. However, as described above, during the hole excavation work, operations such as normal rotation / reverse rotation or operation / stop of the three-phase AC motor 70 are normally repeated. In order to completely prevent the phase loss operation, the cabtyre cable 82 or the like is originally provided so that there is no possibility of the phase loss operation every time the forward rotation / reverse rotation or the operation / stop operation is performed. Although it is desirable for the field worker to confirm the connection state of the wiring members, this is not easy to withstand, resulting in an excessive burden on the field worker and extremely low work efficiency.

  The present invention has been made in view of the above-described circumstances, and completely prevents the open-phase operation of the three-phase AC motor without increasing the burden on site workers and without causing a decrease in work efficiency. It aims to provide a construction machine that can do this.

As means for solving the above problems, the invention according to claim 1 is:
A three-phase AC motor that drives a driven part based on a three-phase AC supplied from a main power source via a cable member and causes the driven part to perform a predetermined operation for the construction work is provided. Is a construction machine that repeatedly operates or stops the operation of this three-phase AC motor.
An operation switch interposed between the main power source and the three-phase AC motor;
An operation switch for causing the operation switch to perform an on operation or an off operation;
When the operation switch is in an OFF state, a current for detecting a phase loss that is a minute DC current is supplied to the three-phase AC motor via the cable member. Based on the presence or absence of interruption, a detection operation is performed to determine whether or not a phase loss has occurred in the three-phase AC supplied from the main power source to the three-phase AC motor via the cable member. An open phase detection circuit that prohibits the on-operation of the operation switch when it is detected,
With
The phase loss detection circuit is
A phase loss detection switch having three normally open contacts that are turned on when a predetermined phase loss detection condition is established by being connected to the cable member of each phase;
Two open phase detection relay coils respectively connected to two of the three normally open contacts;
A current supply power source for supplying an open phase detection current to the three-phase AC motor side via the two open phase detection relay coils and the open phase detection switch in an on-operation;
When at least one of the two relays for phase loss detection is not excited, it is determined that there is a phase loss.
It is characterized by that.

  According to a second aspect of the present invention, in the first aspect of the present invention, the operation switch includes a forward rotation switch and a reverse rotation switch that perform an ON operation when the three-phase AC motor is rotated forward and reverse, respectively. It is composed.

  According to a third aspect of the present invention, in the first or second aspect of the invention, the driven portion is an auger screw that is rotationally driven by the three-phase AC motor via a speed reducer or without a speed reducer. It is characterized by being.

  According to the present invention, the phase loss detection circuit performs a phase loss operation as to whether or not phase loss has occurred, and when phase loss is detected, the phase loss detection circuit is inserted between the main power source and the three-phase AC motor. The operation switch is prohibited from being turned on, so that the three-phase AC motor can be operated in a phase-free manner without increasing the burden on site workers and without reducing work efficiency. It becomes possible to prevent completely.

  FIG. 1 is a configuration diagram of a first embodiment of the present invention. This first embodiment is not limited to the construction machine provided with the hole excavator shown in FIG. 6, and can be widely applied to construction machines equipped with a three-phase AC motor.

  In FIG. 1, the three-phase AC power sent from the main power source 1 passes through the operation switch 2, and further passes through the cabtyre cable 3 connected between the control panel side terminal ST and the motor side terminal MT. The three-phase AC motor 4 that drives the driven part 5 is supplied.

  The operation switch 2 performs an on operation or an off operation based on the operation control signal S1 from the operation switch 6. In addition, an open phase detection circuit 7 is connected between the operation switch 2 and the control panel side terminal ST, and the open phase detection circuit 7 opens and closes the operation if any of the three phases is open. The on operation prohibition signal S2 is output to the device 2.

  Here, the phase loss that is the detection target of the phase loss detection circuit 7 will be described. When the phase loss detection circuit 7 detects the phase loss, when the motor winding of any phase of the three-phase AC motor 4 is burned out, the cable member such as the cabtire cable 3 is cut or misconnected. Sometimes there are cases. The former case is referred to as “internal phase loss”, and the latter case is referred to as “external phase loss”, but the phase loss detection circuit 7 is targeted for detection of the external phase loss. That is, even if the motor winding of any phase of the three-phase AC motor 4 burns out, the phase loss detection circuit 7 will not detect the phase loss if the winding connection of the delta connection method is used. On the other hand, if a phase loss due to disconnection or erroneous connection occurs in a cable member such as the cabtire cable 3, the phase loss detection circuit 7 detects the phase loss regardless of the connection method of the three-phase AC motor 4.

  The “cable member” includes a wide range of electric parts such as various sensors and connecting devices in addition to the wire rod such as the cabtyre cable 3. Further, in practice, a main power circuit breaker, an earth leakage breaker, and the like are provided between the main power source 1 and the operation switch 2, but these members are shown for ease of understanding and for the convenience of the drawings. Is omitted.

  Next, the operation of FIG. 1 will be described. Initially, the main power circuit breaker (not shown) is turned on, but the operation switch 2 is turned off, and therefore the three-phase AC motor 4 is stopped. In this state, the phase loss detection circuit 7 supplies a minute DC current to the three-phase AC motor 4 via the three cabtyre cables 3 for each phase.

  At this time, if any of the three cabtyre cables 3 is disconnected or misconnected, a direct current is cut off in the cabtyre cable 3. The phase loss detection circuit 7 detects phase loss by this current interruption, and outputs an ON operation prohibition signal S2 to the operation switch 2. Therefore, even if the operator operates the operation switch 6 after this and outputs the operation control signal S1 for turning on the operation switch 2, the operation switch 2 is not turned on.

  On the other hand, if the three cabtyre cables 3 are normally connected and no phase loss has occurred, the phase loss detection circuit 7 does not output the ON operation inhibition signal S2. Therefore, after that, if the operator operates the operation switch 6 to output the operation control signal S1 for turning on the operation switch 2, the operation switch 2 is turned on, and the three-phase from the main power source 1 is output. AC power is supplied to the three-phase AC motor 4, and the three-phase AC motor 4 starts driving the driven part 5.

  According to the configuration of FIG. 1 described above, a construction machine operator does not need to be aware of the detection operation of the phase loss detection circuit 7 during normal operation, and operates the operation switch 6 according to the conventional procedure. Then, the operation switch 2 may be made to perform an on / off operation. When the phase loss detection circuit 7 detects the phase loss and the operation switch 6 is operated to turn the operation switch 2 on, the connection state of the cabtyre cable 3 and other electrical components is lost. Is checked again, and after the phase loss state is resolved, the operation switch 6 is operated again to turn on the operation switch 2. Therefore, according to the configuration of FIG. 1, it is possible to completely prevent the three-phase AC motor 4 from being phased out without increasing the burden on the field worker and without causing a reduction in work efficiency.

  Next, a second embodiment of the present invention will be described with reference to FIGS. This second embodiment is a more specific example of the configuration of the first embodiment described above, and is assumed to be applied to a construction machine including the hole excavator shown in FIG. Yes. The configurations of FIGS. 3 to 5 are originally easy to see when illustrated in FIG. 2, but are inevitably illustrated as separate drawings due to space limitations in the drawings.

  FIG. 2 is a configuration diagram of a part of the main circuit and the phase loss detection circuit of the second embodiment. In this figure, three-phase AC power is sent to terminals of R, S, and T phases from a main power source and a main power circuit breaker which are not shown. This three-phase AC power is connected between the control panel side terminal ST and the motor side terminal MT via the forward switch 2F having the normally open contact F1MC or the reverse switch 2R having the normally open contact R1MC. The three-phase AC motor 4 that drives the driven part 5 is supplied via the cabtyre cable 3. The driven portion 5 corresponds to the speed reducer 71 and the auger screw 72 in FIG.

  Between the R phase and the T phase, input terminals R1 and T1 of an AC / DC converter 9 as a power supply for current supply are connected. The AC / DC converter 9 has DC output terminals P1 and N1, and the positive output terminal P1 is connected to the R phase via one normally open contact 3X of the phase loss detection switch 8. The minus side output terminal N1 is connected to the S phase and the T phase via two normally open contacts 3X of the phase loss detection relay coils 1X and 2X and the phase loss detection switch 8. These phase loss detection switches 8, phase loss detection relay coils 1X, 2X, and AC / DC converter 9 correspond to a part of the phase loss detection circuit 7 in FIG.

  In addition, between the R phase and the T phase to which the input terminals R1 and T1 are connected, a main power indicator lamp L1 indicating that the main power breaker is in an on state, terminals R2 and T2 (described later in FIG. 3) ), And lines R3 and T3 (described later in FIG. 5). Further, lines P3 and N3 (described later in FIG. 4) are connected to the output terminals P1 and N1.

  FIG. 3 is a detailed configuration diagram of the phase loss detection circuit components, operation switches, and the like not shown in FIG. In this figure, an operation panel 10 and a control panel 11 correspond to the operation panel 80 and the control panel 81 in FIG. 6, respectively. The phase loss detection switch 8, the phase loss detection relay coils 1X and 2X, and the AC / DC converter 9 shown in FIG. 2 are also provided in the control panel 11.

  In the operation panel 10, a power switch 13, a power display lamp L2, a phase loss display lamp L3, stop switches 14 and 15, a forward rotation switch 16, and a reverse rotation switch 17 are disposed. The stop switches 14 and 15, the forward rotation switch 16, and the reverse rotation switch 17 correspond to the operation switch 6 described in FIG. The stop switches 14 and 15 are operated in conjunction with each other. The reason why the two stop switches are used in this way is that the operation is always stopped when one of them normally operates, and the certainty of the stop operation is ensured.

  The AC / DC converter 12 disposed in the control panel 11 functions as a signal control power source and has input terminals R2 and T2 and output terminals P2 and N2. The input terminals R2 and T2 are connected to the R phase and T phase of the main circuit shown in FIG.

  One end of the power switch 13 is connected to the plus output terminal P2, and one end of the phase loss indicator lamp L3 is also connected to the plus output terminal P2 via the normally open contact 7X. Further, one end side of the power supply display lamp L2 is connected to the other end side of the phase loss display lamp L3 and also connected to the minus side output terminal N2.

  One end side of the forward rotation switch 16 is connected to one end side of the forward rotation relay coil F1X and the forward rotation timer relay coil TLR3 via a normally closed contact 7X and a normally closed contact R1X. One end of the reverse switch 17 is connected to the reverse relay coil R1X and the reverse timer relay coil TLR4 via the normally closed contact 7X and the normally closed contact F1X. The other ends of these coils TLR3, F1X, R1X, and TLR4 are connected to the negative output terminal N2. Further, one end of the stop switch 15 is connected to the normally open contact 7X on the forward relay side and the normally open contact 7X on the reverse relay side through the normally open contacts F1X and R1X, respectively.

  FIG. 4 is a detailed configuration diagram of the phase loss detection circuit components not shown in FIG. In this figure, lines P3 and N3 are connected to the output terminals P1 and N1 of the AC / DC converter 9 shown in FIG. Between the lines P3 and N3, as shown in the figure, a circuit formed of various contacts and coils and having various functions is inserted.

  That is, the circuit composed of the normally closed contacts F1X, R1X and the relay coil 4X is a circuit for determining whether or not the phase loss detection condition is satisfied, and the circuit composed of the normally open contact 4X and the on-delay relay coil TLR1 is missing. This is a circuit for generating a time lag when the phase detection condition is satisfied.

  The circuit consisting of the on-delay normally-open contact TLR1 and normally-open contact 4X, relay coils 3X and 5X, and on-delay relay coil TLR2 has a circuit for supplying a current for detecting a phase loss, and a phase loss detection operation. A circuit for starting and a circuit for generating a time lag when determining the presence of phase loss.

  Furthermore, the circuit consisting of the normally open contacts 1X and 2X and the relay coil 6X connected to the normally open contact 5X is a circuit when it is determined that there is no phase loss, and is connected to the normally open contact 5X. The contact 6X and the on-delay normally closed contact TLR2 are circuits when it is determined that there is a phase failure.

  FIG. 5 is a detailed block diagram of a component part of the phase loss detection circuit not shown in FIG. In this figure, lines R3 and T3 are connected to the R phase and T phase of the main circuit shown in FIG. Between the lines R3 and T3, as shown in the figure, a normal rotation main circuit formed by an on-delay normally open contact TLR3, a normally closed contact 3X, a normally closed contact R1MC, and a normal rotation relay coil F1MC, An on-delay normally open contact TLR4, a normally closed contact 3X, a normally closed contact F1MC, and a reverse main circuit formed by a reverse relay coil R1MC are inserted.

  Next, the operation of the second embodiment configured as described above will be described. First, the case where the cabtyre cable 3 and other electrical components are correctly connected and no phase failure has actually occurred will be described. In FIG. 2, when an operator turns on the main power circuit breaker (not shown), the main power indicator lamp L1 is turned on, and an AC voltage is input to the input terminals R1 and T1 of the AC / DC converter 9. . The AC / DC converter 9 converts this AC voltage into a DC voltage and outputs it from the output terminals P1 and N1. Therefore, a DC voltage is also generated between the lines P3 and N3.

  When a DC voltage is generated between the lines P1 and N1, the “phase loss detection condition” in FIG. 4 is satisfied (the contacts F1X and R1X are in the ON state), and the coil 4X is excited. Since the contact 4X is turned on by exciting the coil 4X, the coil TLR1 is excited. When the coil TLR1 is excited, the contact TLR1 is turned on with a delay of one shot (for example, about 0.5 seconds). Due to this one-shot delay, the contact TLR1 is always turned on after the contact 4X below it is turned on, and the phase loss occurs before the contact 4X is turned on, that is, before the phase loss detection condition is satisfied. It is prevented that detection current is supplied and phase loss detection is started.

  Now, when the contacts TLR1, 4X are turned on, the coils 3X, 5X, TLR2 are excited. Since the contact 3X of the phase loss detection switch 8 (Fig. 2) is turned on by exciting the coil 3X, the phase loss detection relay coils 1X and 2X are excited by the DC current from the output terminals P1 and N1 (see above). In this case, it is assumed that no phase loss actually occurs).

  When the coils 1X and 2X are energized, the contacts 1X and 2X in “no phase loss” in FIG. 4 are turned on. Since the contact 5X is also turned on by the excitation of the coil 5X, the coil 6X is excited. The fact that the coil 6X is excited means that the phase loss detection circuit has determined that there is no phase loss (however, in the case of “no phase loss”, display operation by a lamp or the like) Is not done).

  Further, when the coil 6X is energized, the normally closed contact 6X in “with phase loss” is turned off. Therefore, even if the contact TLR2 is turned on when one shot is delayed due to the excitation of the coil TLR2, the coil 7X is not excited.

  When the operator turns on the main power breaker, the phase loss detection circuit determines that no phase loss has occurred in any of the three-phase alternating currents as described above. Thereafter, the operator operates the power switch 13 in the operation panel 10 in FIG. 3 to be turned on. At this time, the AC / DC converter 12 inputs AC voltages from the main circuit R-phase and T-phase to its input terminals R2 and T2, converts them into DC voltages, and outputs them from the output terminals P2 and N2. Therefore, the power display lamp L2 is lit. On the other hand, the phase loss indicator lamp L3 is not lit (because the coil 7X in “with phase loss” in FIG. 4 is not energized and the contact point 7X maintains the OFF state).

  Next, the operator confirms that the phase loss indicator lamp L3 is in the off state (although there is no particular problem if the confirmation is forgotten), the forward rotation switch for causing the three-phase AC motor 4 to rotate forward, for example. Press 16 with your finger to turn it on. When the forward switch 16 is turned on, the forward relay coil F1X and the forward timer relay coil TLR3 are excited (contacts 7X and R1X are in the on state). Since the self-holding contact F1X is held in the ON state by the excitation of the coil F1X, the excitation of the coils F1X and TLR3 is continued even after the operator releases the finger and the forward rotation switch 16 is turned OFF. .

  Excitation of the coil F1X in FIG. 3 turns off the contact F1X in the “open phase detection condition” in FIG. 4, so that the excitation of the coil 4X is released and the contact 4X returns to the off state. Therefore, since the excitation of the coil 3X in the “phase loss detection current supply” in FIG. 4 is also released, the contact 3X in the “forward rotation main circuit” in FIG. 5 is also in the ON state. Further, the excitation of the forward rotation timer relay coil TLR3 causes the contact TLR3 to be turned on with a one-shot delay, thereby exciting the coil F1MC. At this time, the contact 3X of the phase loss detection switch 8 (FIG. 2) is turned off by the excitation release of the coil 3X, and the supply of DC current from the output terminals P1 and N1 is stopped.

  By the excitation of the coil F1MC in FIG. 5, the contact F1MC of the forward rotation switch 2F in FIG. 2 is turned on. Accordingly, the three-phase AC power from the main power supply is supplied to the three-phase AC motor 4 via the forward rotation switch 2F and the cabtyre cable 3, and the three-phase AC motor 4 drives the driven portion 5.

  In addition, since it becomes the same operation | movement as the above also when a driving | operation worker operates reverse switch 17 to reversely rotate the three-phase alternating current motor 4, it abbreviate | omits about the description.

  In order to stop the forward rotation of the three-phase AC motor 4, the driving operator pushes one of the stop switches 14 and 15 in FIG. When the stop switches 14 and 15 are turned off, the excitation of the coils F1X and TLR3 is released. When the excitation of the coil TLR3 is released, the contact TLR3 in the “forward rotation main circuit” of FIG. 5 is immediately turned off, and the excitation of the coil F1MC is released. Accordingly, the contact F1MC of the forward rotation switch 2F in FIG. 2 is also turned off, and the supply of the three-phase AC power from the main power supply is cut off, so that the forward rotation of the three-phase AC motor 4 is stopped. Even after the operator releases his / her finger and the stop switches 14 and 15 return to the ON state, the coils F1X and TLR3 are not excited because the self-holding contact F1X has already been turned off.

  Next, a description will be given of a case where an open phase has occurred due to disconnection or erroneous connection of the cabtyre cable 3. Similarly to the above case, when the operator turns on the main power circuit breaker not shown in FIG. 2, the main power indicator lamp L1 is turned on, and the input / output terminals R1, T1 of the AC / DC converter 9 are turned on. AC voltage is input to. The AC / DC converter 9 converts this AC voltage into a DC voltage and outputs it from the output terminals P1 and N1. Therefore, a DC voltage is also generated between the lines P3 and N3.

  When a DC voltage is generated between the lines P1 and N1, the “phase loss detection condition” in FIG. 4 is satisfied (the contacts F1X and R1X are in the ON state), and the coil 4X is excited. Since the contact 4X is turned on by exciting the coil 4X, the coil TLR1 is excited. When the coil TLR1 is excited, the contact TLR1 is turned on with a delay of one shot (for example, about 0.5 seconds).

  When the contacts TLR1, 4X are turned on, the coils 3X, 5X, TLR2 are excited. Since the contact 3X of the phase loss detection switch 8 (FIG. 2) is turned on by the excitation of the coil 3X, DC current tends to flow through the phase loss detection relay coils 1X and 2X from the output terminals P1 and N1. However, since phase loss actually occurs, current should not flow through at least one of the coils 1X and 2X.

  Therefore, since one of the contacts 1X and 2X in “no phase loss” in FIG. 4 is in an off state, the coil 6X is not excited and the contact 6X in “with phase loss” is in an on state. Therefore, the coil 7X is excited when the contact point TLR2 is turned on.

  Thereafter, the operator operates to turn on the power switch 13 in the operation panel 10 in FIG. At this time, the AC / DC converter 12 inputs AC voltages from the main circuit R-phase and T-phase to its input terminals R2 and T2, converts them into DC voltages, and outputs them from the output terminals P2 and N2. Therefore, the power display lamp L2 is lit. Further, since the contact 7X is turned on by exciting the coil 7X in “with phase loss” in FIG. 4, the phase loss display lamp L3 is also lit.

  The operator stops turning on the forward switch 16 by turning on the phase loss indicator lamp L3. Then, the main power circuit breaker is shut off, the connection state of the cabtyre cable 3 and the like is checked, and after the connection is made normally, the main power circuit breaker is turned on again. Then, the phase loss detection circuit performs the phase loss detection operation again, but this time the phase loss display lamp L3 is turned off in order to determine whether there is no phase loss. Thereafter, the operator only needs to turn on the forward rotation switch 16.

  Here, even if the phase loss indicator lamp L3 is lit, the operator may overlook this and operate the forward switch 16 to turn on. In the case of a conventional construction machine, the reduction gear 71 shown in FIG. 6 is damaged in such a case, but according to the configuration of the second embodiment, such a situation can be avoided. it can.

  That is, in FIG. 3, the normally closed contact 7 </ b> X of the “forward relay” is turned off even if the operator turns on the forward switch 16 even though the phase loss indicator lamp L <b> 3 is lit. Therefore, the coils F1X and TLR3 are not excited (the coil 7X “with phase loss” in FIG. 4 is excited). Accordingly, since the contact TLR3 in the “forward rotation main circuit” of FIG. 5 is maintained in the OFF state, the coil F1MC is not excited, and the contact F1MC of the forward rotation switch 2F of FIG. 2 is not turned on. That is, since the three-phase AC power is not supplied to the three-phase AC motor 4, the driven part 5 is not driven and the speed reducer 71 is not damaged.

The block diagram of the 1st Embodiment of this invention. The block diagram about a part of main circuit and phase loss detection circuit of the 2nd Embodiment of this invention. FIG. 3 is a detailed configuration diagram of a phase loss detection circuit configuration portion, an operation switch, and the like that are not illustrated in FIG. 2. FIG. 3 is a detailed configuration diagram of a phase loss detection circuit component not shown in FIG. 2. FIG. 3 is a detailed configuration diagram of a phase loss detection circuit component not shown in FIG. 2. Explanatory drawing which shows the structure of the whole conventional construction machine.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Main power supply 2 Driving switch 3 Cabtire cable 4 Three-phase AC motor 5 Driven part 6 Operation switch 7 Phase loss detection circuit 2F Forward rotation switch 2R Reverse rotation switch 8 Phase loss detection switch 1X, 2X Phase loss Relay coil for detection 9 AC / DC converter
L1 Main power indicator
L2 Power indicator
L3 Phase loss indicator lamps 14, 15 Stop switch (running switch)
16 Forward switch (running switch)
17 Reverse switch (running switch)

Claims (3)

A three-phase AC motor that drives a driven part based on a three-phase AC supplied from a main power source via a cable member and causes the driven part to perform a predetermined operation for the construction work is provided. Is a construction machine that repeatedly operates or stops the operation of this three-phase AC motor.
An operation switch interposed between the main power source and the three-phase AC motor;
An operation switch for causing the operation switch to perform an on operation or an off operation;
When the operation switch is in an OFF state, a current for detecting a phase loss that is a minute DC current is supplied to the three-phase AC motor via the cable member. Based on the presence or absence of interruption, a detection operation is performed to determine whether or not a phase loss has occurred in the three-phase AC supplied from the main power source to the three-phase AC motor via the cable member. An open phase detection circuit that prohibits the on-operation of the operation switch when it is detected,
With
The phase loss detection circuit is
A phase loss detection switch having three normally open contacts that are turned on when a predetermined phase loss detection condition is established by being connected to the cable member of each phase;
Two open phase detection relay coils respectively connected to two of the three normally open contacts;
A current supply power source for supplying an open phase detection current to the three-phase AC motor side via the two open phase detection relay coils and the open phase detection switch in an on-operation;
When at least one of the two relays for phase loss detection is not excited, it is determined that there is a phase loss.
Construction machinery characterized by that. The operation switch, the is 3-phase AC motor which is constituted by the forward rotation switch and the reverse rotation switch to perform ON operation in case of forward rotation and reverse rotation, respectively, according to claim 1 Symbol, characterized in that Listed construction machinery. Said driven unit via a reduction gear, or without using a reduction gear, wherein a auger screw is rotationally driven by 3-phase AC motor, according to claim 1 or 2 SL placement of the construction machine, characterized in that .

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