JP2016084205A - Driving device for electric winch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device for an electric winch that can safely recover regenerative power while making a free fall movement.SOLUTION: A driving device comprises: an AC motor 16; a DC power supply 30; an inverter 32; a voltage step-down circuit 34 interposed between the inverter 32 and the DC power supply 30; a stationary driving circuit 36 that is provided in parallel with the voltage step-down circuit 34 and can be switched between a permission state where flowing of currents from the inverter 32 into the DC power supply 30 is permitted by bypassing the voltage step-down circuit 34 and an inhibition state where the flowing is inhibited; and a free fall control portion. The free fall control portion, when rotation speed in winding-down direction of the AC motor 16 exceeds voltage step-down determination speed and when receiving an instruction to brake a winch drum, brings the stationary driving circuit 36 into the inhibition state and activates the voltage step-down circuit 34 so as to generate regenerative power, and when the rotation speed is equal to the voltage step-down determination speed or less, stops the voltage step-down circuit 34 and brings the stationary driving circuit 36 into the permission state.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an apparatus for driving an electric winch used for a crane or the like and having a free fall control function.

  In recent years, it has been studied to use an electric winch driven by an electric motor as a winch that is mounted on a crane or the like and performs a hanging work. The use of this electric winch has an advantage that it is possible to recover kinetic energy (rotational energy of the electric motor) generated by the lowering of the object when the object is rolled down and convert it into electric energy, that is, regenerate. .

  As an electric winch having such a regeneration function and a driving device thereof, those disclosed in Patent Document 1 are known. The electric winch disclosed herein is mounted on a crane, and an apparatus for driving the electric winch supplies an electric motor and electric power to the electric motor and is generated by power generation of the motor when the electric winch is lowered. A battery for storing electric power.

JP2013-71810A

  There is a so-called free-fall action that lowers the suspended load at a speed close to free fall as a special action when the crane is being lowered, but if a conventional electric winch performs regeneration while performing the free-fall action, the circuit voltage May rise excessively and cause damage to the battery. That is, in the free fall operation, the winch drum of the electric winch and the electric motor connected to the electric winch rotate at a high speed as the suspended load descends at a speed close to the free fall speed. If an excessively induced voltage is generated in the battery and applied to the battery, the battery may be damaged.

  This situation can be avoided by separating the drive device including the battery and the electric motor from the winch drum by a clutch. In this case, the regenerative power cannot be recovered during free fall.

  An object of the present invention is to solve the above-described problem, that is, to provide a drive device for an electric winch that can safely recover regenerative power while performing a free fall operation.

  In order to achieve the above object, the present inventors have provided between an AC motor for rotating a winch drum of the electric winch and an inverter connected thereto, and a DC power source for driving the AC motor. It has been conceived to prevent an excessive voltage from being applied to the DC power supply by interposing a step-down circuit and dropping the voltage generated in the inverter during the free fall operation by the step-down circuit. However, since driving of the step-down circuit generally involves a large energy loss (for example, switching loss due to frequent on / off operation of switching elements included in the step-down circuit), a significant reduction in driving efficiency of the electric winch cannot be avoided.

  The present invention provides a drive device for an electric winch that can achieve the above-mentioned object while avoiding a significant decrease in the drive efficiency. Specifically, this apparatus is connected to a winch drum of the electric winch to rotate the winch drum and generate regenerative electric power along with the rotation of the winch drum, and to drive the AC electric motor. A direct current power source for supplying electric power, an inverter interposed between the direct current power source and the alternating current motor, and a voltage generated in the inverter when the alternating current motor rotates in a winding direction. A step-down circuit for lowering the voltage to be generated and a step-down circuit that is provided in parallel with the step-down circuit and can be switched between an allowable state that allows current flow from the inverter to the DC power supply and a blocking state that blocks the step-down circuit. And a free fall control unit that controls the driving of the AC motor. The free fall control unit controls the steady drive circuit in the blocked state when the rotational speed in the winding direction of the AC motor exceeds a preset step-down determination speed and an instruction to brake the winch drum is given. The step-down control is performed to activate the step-down circuit to generate regenerative power, and when the rotational speed in the winding direction of the AC motor is equal to or lower than the step-down determination speed, the step-down circuit is stopped and the steady drive is performed. Put the circuit in the tolerance state.

  According to this apparatus, while performing a free fall operation using the electric winch, it is possible to safely recover the electric power generated in the AC motor during the free fall operation without significantly reducing efficiency. Specifically, when the rotation speed (rotation in the lowering direction) of the AC motor accompanying the free fall operation is equal to or lower than the step-down determination speed, the free fall control unit switches the steady drive circuit to an allowable state, The electric power generated in the AC motor can be sent to the DC power source via the inverter and further the steady drive circuit, that is, bypassing the step-down circuit, thereby comparing with the case of passing through the step-down circuit. Regeneration can be performed with high efficiency. On the other hand, when the rotational speed of the AC motor accompanying the free fall operation exceeds the step-down determination speed, that is, when the induced voltage of the AC motor is high, the free fall control unit blocks the steady drive circuit. In addition, by performing step-down control by operating the step-down circuit, a battery that constitutes the direct-current power supply while suppressing the voltage applied to the direct-current power supply to a safe voltage regardless of the high induced voltage in the alternating-current motor The electric power generated by the AC electric motor can be recovered while avoiding the damage.

  The drive device according to the present invention further includes a braking operation device that is operated to instruct the magnitude of the braking force as means for giving the braking instruction to the free fall control unit, the free fall control It is preferable that the unit performs the step-down control so that the degree of step-down by the step-down circuit decreases as the braking force instructed by the brake operation unit increases. Since the braking action by the regenerative operation becomes larger as the degree of pressure reduction is smaller, the combination of the brake operation device and the pressure reduction control enables the operation of the electric winch that matches the intention of the operator.

  For example, in the case where the step-down circuit includes a coil inductance and a switching element, the step-down control can be performed based on the on / off duty ratio of the switching element. In this case, since the energy loss due to on / off of the switching element is large, the effect of the parallel drive circuit is particularly remarkable.

  The drive device according to the present invention is interposed between the DC power supply and the inverter and is provided in parallel with the steady drive circuit, and the voltage supplied from the DC power supply to the inverter is increased above the voltage of the DC power supply. A step-up circuit for causing the free-fall controller to rotate when the rotational speed of the AC motor in the winding-down direction exceeds a preset step-up determination speed and no instruction is given to brake the winch drum. It is preferable that the steady driving circuit is set to the blocking state and the boosting circuit is operated to perform the boosting control.

  The boosting by the boosting circuit prevents or suppresses the regenerative operation due to the flow of current from the AC motor and inverter to the DC power supply, and also the braking of the AC motor due to this, thereby suppressing the decrease in the descent speed. It is possible to realize free fall control in accordance with the operator's intention of not instructing braking. Specifically, when the rotational speed of the AC motor in the free fall operation is high and the induced voltage is relatively high with respect to the voltage of the DC power source, current flows from the inverter to the DC power source by the power generated by the AC motor. A regenerative operation occurs, and this regenerative operation is accompanied by a braking action on the AC motor, so that the rotational speed of the AC motor is suppressed even though the operator does not give a brake instruction. The step-up operation performed by the step-up circuit prevents or suppresses the flow of current from the AC motor and inverter to the DC power source, that is, regenerative operation, thereby preventing or suppressing braking of the AC motor by the regenerative operation. Thus, the rotational speed of the AC motor can be made close to the speed required by the operator.

  In this case, it is preferable that the free fall control unit performs the step-up control so that the degree of step-up by the step-up circuit increases as the rotational speed of the AC motor increases. The boost control makes it possible to prevent or suppress braking of the AC motor due to the regenerative operation while avoiding an excessive boost operation.

  In addition, the free fall control unit determines whether or not the braking instruction is given when the rotation speed of the AC motor is a preset maximum allowable speed and exceeds the step-down determination speed and the step-up determination speed. Regardless, it is preferable to perform forced voltage step-down control that forces the voltage step-down circuit to perform a step-down operation. This forced step-down control makes it possible to prevent the AC motor and other components from being damaged due to the rotation of the AC motor at an excessive speed.

  As the steady drive circuit, for example, a switching element that is provided in a path connecting the DC power source and the inverter and that is switched between a state in which the path is made conductive and a state in which the path is disconnected, and a switching element that is provided in parallel with the switching element are provided. And a diode that only allows a current to pass from the DC power source to the inverter. The steady driving circuit can always be allowed to supply power from the DC power source to the AC motor by the diode, and can be switched between the allowed state and the blocked state by turning on and off the switching element.

  The free fall control unit is configured to control the AC motor when the rotational speed in the winding direction of the AC motor is equal to or lower than the step-down determination speed (when step-up control is also performed, the step-down determination speed is equal to or lower than the step-up determination speed). Regenerative control by operating the inverter may be performed according to a designated braking force.

  As described above, according to the present invention, there is provided a drive device for an electric winch capable of safely recovering regenerative power without performing a significant fall in efficiency while performing a free fall operation.

It is a schematic diagram which shows the structure of the electric winch which concerns on embodiment of this invention, and its drive device. It is a figure which shows the drive circuit contained in the said drive device. It is a block diagram which shows the main function structures of the controller contained in the said drive device. It is a flowchart which shows the main control operations which the said controller performs.

  Preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows the main part of a crane equipped with an electric winch and its drive device according to this embodiment. The crane includes a boom 2 that can be raised and lowered, and a rope 4 for suspension. The electric winch includes a winch drum 10 that can rotate about a horizontal axis. A portion including one end of the rope 4 is wound around the winch drum 10, and a portion including the other end hangs down from a sheave 3 provided at the tip of the boom 2. A hook device 6 is connected to the other end, and a suspended load 8 is engaged with the hook device 6.

  The electric winch can raise and lower the suspended load 8 by rotating the winch drum 10 in the winding direction and the lowering direction. The operation based on the rotation in the lowering direction includes a so-called free fall operation. In this free fall operation, the drive of the winch drum 10 is controlled so as to allow the suspended load 8 to descend at a speed close to the free fall speed.

  The drive device for the electric winch includes an AC electric motor 16, a drive circuit 18, a controller 20, a winch operation device 22, a braking operation device 23, and a free fall permission switch 24.

  The AC motor 16 has a rotatable output shaft. The output shaft is connected to the rotation shaft of the winch drum 10 via the speed reducer 12, the clutch 14, and the like. Accordingly, the winch drum 10 can be rotationally driven by the operation of the AC motor 16. Further, the AC motor 16 has a function of generating regenerative electric power by rotating the output shaft along with the rotation of the winch drum 10 in the lowering direction.

  The drive circuit 18 includes a DC power source, supplies power to the AC motor 16 to rotate its output shaft, and performs a regenerative operation for collecting and storing power generated by the AC motor 16 during the lowering operation. It has a function.

  As will be described in detail later, the controller 20 controls the operation of the drive circuit 18 by inputting a control signal to the components included in the drive circuit 18. The controller 20 includes a rotation detection signal generated by an encoder (not shown) built in the AC motor 16 as signals necessary for the control operation, the winch operation device 22, the brake operation device 23, and a free fall permission switch. The command signal generated by 24 is input.

  The winch operation device 22 has an operation lever 26 that can be operated from the neutral position to the winding upper side and the lower winding side, respectively. The winch operation device 22 generates a winding command signal or a lowering command signal corresponding to the operation direction and the operation amount of the operation lever 26 and inputs this to the controller 20.

  The brake operating device 23 is for giving an instruction to the controller 20 regarding braking of the winch drum 10 and the AC motor 16 during the free fall operation. Specifically, the brake operation unit 23 includes a brake pedal 28 that receives a depression operation, and generates a brake command signal corresponding to the depression of the brake pedal 28 and inputs it to the controller 20. The braking command signal is a signal for instructing the magnitude of the braking force. The brake operating device 23 generates a braking command signal that indicates a larger braking force as the depression amount of the brake pedal 28 is larger.

  The free fall permission switch 24 is operated by an operator to give the controller 20 permission for a free fall operation. Specifically, the free fall permission switch 24 generates a free fall permission signal and inputs the free fall permission signal to the controller 20 when operated.

  FIG. 2 shows a specific configuration of the drive circuit 18. The drive circuit 18 includes a battery 30, an inverter 32, a buck-boost converter 34, a steady drive circuit 36, and a smoothing capacitor 37.

  The battery 30 has both a function as a direct current power source and a function as a battery. Specifically, the battery 30 supplies electric power necessary for driving the AC motor 16, mainly driving in the winding direction, to the AC motor 16, while rotating the AC motor 16 in the winding direction (free fall). A function of accumulating regenerative power generated by the AC motor 16 with the rotation during operation).

  The inverter 32 is interposed between the AC motor 16 and the battery 30, and performs DC / AC conversion necessary for power transfer between the two. Specifically, the AC motor 16 illustrated in FIG. 2 is a three-phase AC motor having a U phase, a V phase, and a W phase, and the inverter 32 includes a plurality of switching units 38 (switching elements and switching elements) corresponding to each phase. A combination with a diode).

  The step-up / down converter 34 is interposed between the battery 30 and the inverter 32 and has both a function as a step-down circuit and a function as a step-up circuit. The function as the step-down circuit is applied to the battery 30 rather than the voltage generated between the battery-side terminal pair of the inverter 32 by causing the AC motor 16 to rotate in the winding direction to generate an induced voltage. This is a function to reduce the voltage that is generated. The function as the booster circuit is a function of raising the voltage applied between the battery 30 and the battery-side terminal pair of the inverter 32 more than the voltage between the terminals of the battery 30.

  Specifically, the step-up / step-down converter 34 includes a choke coil 40 having inductance, a step-down switching element 42, a step-up switching element 44, a step-down diode 46, and a step-up diode 48. The choke coil 40 is arranged in series with the battery 30 and is connected to the positive terminal of the battery 30. The step-down switching element 42 is interposed between the choke coil 40 and the high-voltage side terminal of the inverter 32, and the step-up switching element 44 is interposed between the choke coil 40 and the low-voltage side terminal of the inverter 32. Intervene in. The step-down diode 46 is interposed between the choke coil 40 and the low-voltage side terminal of the inverter 32 while being arranged in parallel with the step-up switching element 44. The step-up diode 48 is interposed between the choke coil 40 and the high-voltage side terminal of the inverter 32 while being arranged in parallel with the step-down switching element 42.

  The steady drive circuit 36 is a circuit provided in parallel with the step-up / step-down converter 34 between the positive terminal of the battery 30 and the high-voltage side terminal of the inverter 32, and bypasses the step-up / down converter 34. This is a circuit that can be switched between an allowable state in which current flows from the inverter 32 to the positive terminal of the battery 30 and a blocking state in which this current is blocked.

  Specifically, the steady drive circuit 36 according to this embodiment has both the switching element 50 and the diode 52 arranged in parallel with each other. The switching element 50 is provided in a path connecting the positive terminal of the battery 30 and the high-voltage side terminal of the inverter 32, and is switched between an on state for conducting the path and an off state for disconnecting. Accordingly, the steady driving circuit 36 is switched between the allowable state and the blocked state by turning on and off the switching element 50. The diode 52 allows passage of current from the positive terminal of the battery 30 toward the inverter 32 regardless of whether the switching element 50 is turned on or off, but prevents passage of current from the inverter 32 toward the battery 30.

  The operation of the step-up / step-down converter 34 as a step-down circuit, in other words, the regenerative operation, is the on / off switching of the step-down switching element 42 in a state where the switching element 50 of the steady drive circuit 36 is switched off (blocking state). Achieved by: Specifically, when the step-down switching element 42 is on, current flows into the battery 30 from the inverter 32 via the step-down switching element 42 and the choke coil 40, so that energy is stored in the choke coil 40 and choke at the same time. A counter electromotive force is generated in the coil 40 in a direction that prevents an increase in current, and a potential difference is applied between the positive terminal of the battery 30 and the high-voltage side terminal of the inverter 32. Thereafter, when the switching element 42 is switched off, an electromotive force is generated in the choke coil 40 in a direction to maintain the current that has been flowing through the choke coil 40 until the coil 40 → battery 30 → step-down. A current passing through the diode 46 in order is formed. A step-down operation is achieved as described above.

  Therefore, the step-down operation is performed by turning on and off the step-down switching element 42, and the degree of step-down and the magnitude of the braking force can be controlled by setting the duty ratio of the on-state. Specifically, the higher the on-duty ratio of the step-down switching element 42, the higher the voltage applied to the battery 30, and thus the degree of step-down becomes smaller. On the other hand, the braking force applied to the AC motor 16 by the regenerative operation increases.

  The operation of the step-up / step-down converter 34 as a booster circuit is achieved by switching the booster switching element 44 on and off when the switching element 50 of the steady drive circuit 36 is switched off (blocking state). Specifically, when the step-up switching element 44 is ON, a current passing through the battery 30 → the choke coil 40 → the step-up switching element 44 is formed, and energy is stored in the choke coil 40. Thereafter, when the switching element 42 is switched off, a current is formed from the positive terminal of the battery 30 into the inverter 32 via the choke coil 40 and the boosting diode 48, and the choke coil 40 is subjected to the choke until then. An electromotive force directed to maintain the current flowing in the coil 40 is generated, and the voltage applied between the battery-side terminal pair of the inverter 32 becomes higher than the inter-terminal voltage of the battery 30 by that amount. In this way, the boosting operation is achieved.

  Therefore, the step-up operation is performed by turning on / off the step-up switching element 44, and the degree of step-up can be controlled by setting the duty ratio of the on-state. Specifically, the higher the ON duty ratio of the step-up switching element 44, the higher the voltage in the choke coil 40, and thus the degree of step-up increases.

  The smoothing capacitor 37 is interposed between the battery-side terminal pair of the inverter 32 between the inverter 32 and the step-up / down converter 34.

  FIG. 3 shows a main functional configuration of the controller 20 for controlling the operation of the drive circuit 18. The controller 20 includes a control mode determination unit 56, a normal control unit 58, and a free fall control unit 60 shown in FIG.

  The control mode determination unit 56 determines whether or not the operation state grasped by the signal input to the controller 20 corresponds to a preset free fall start condition, and if so, the free fall control unit 60. In this case, the normal control unit 58 is caused to perform normal control. Further, when a predetermined free fall stop condition is satisfied during the free fall control, the free fall control is stopped and switched to the normal control. The free fall start and stop conditions can be set in various ways, and the conditions according to this embodiment will be described in detail later.

  The normal control unit 58 performs normal control, that is, control other than the free fall control. Specifically, the normal control unit 58 inputs a control signal to the inverter 32 of the drive circuit 18 based on the operation on the winding side or the operation on the lowering side given to the operation lever 26 of the winch operation device 22 to exchange the AC motor. The 16 winding driving or lowering driving is controlled.

  The free fall control unit 60 controls the free fall control, that is, the free fall operation. As a function for that purpose, the free fall control unit 60 includes a free fall control mode determination unit 62, a normal free fall control unit 64, a step-down control unit 65, and a step-up control unit 66 shown in FIG.

  The free fall control mode determination unit 62 determines whether to perform normal free fall control, step-down control, or step-up control based on the rotation speed of the AC motor 16. Specifically, the free fall control mode determination unit 62 determines whether or not the rotational speed of the AC motor 16 is equal to or lower than a preset rated speed V1, and if it is equal to or lower than the rated speed V1, it is normal. The free fall control unit 64 performs a normal free fall control operation, and when the rated speed V1 is exceeded, the step-down control unit 65 or the step-up control unit 66 performs step-down control or step-up control (specific step-down / step-up control). The determination will be described in detail later.) Therefore, the rated speed V1 according to this embodiment corresponds to the step-down determination speed and the step-up determination speed referred to in the present invention.

  The rotational speed of the AC motor 16 can be calculated from a rotation detection signal output from an encoder built in the AC motor 16. Further, the rated speed V1 in this embodiment is set to the rotational speed of the AC motor 16 corresponding to the voltage across the terminals of the inverter 32 corresponding to the maximum voltage of the battery 30.

  The normal free fall control unit 64 performs the normal free fall control, that is, free fall control without any step-up control or step-down control. As a feature of this apparatus, the normal free fall control unit 64 turns on the switching element 50 of the steady drive circuit 36 and keeps the switching elements 46 and 48 of the step-up / down converter 34 off as in the normal control. In this state, that is, without passing through the step-up / down converter 34, the normal free fall control is executed.

  The step-down control unit 65 and the step-up control unit 66 perform step-down control and step-up control using the step-up / down converter 34, respectively.

  Next, a specific control operation performed by the controller 20 will be described with reference to the flowchart of FIG.

  First, the control mode determination unit 56 of the controller 20 determines whether or not the current operation state corresponds to a preset free fall start condition. The free fall start conditions according to this embodiment are as follows.

  1) The free fall permission switch 24 is turned on (free fall permission) (step S1).

  2) The brake pedal 28 of the brake operating device 23 is fully operated, that is, it is depressed to the deepest position (step S2).

  3) The parking brake provided for the winch drum 10 is activated (step S3).

  The parking brake may be automatically released when the brake pedal is slightly released from the full depression in step S2, or the parking brake may be operated after the brake pedal 28 is depressed more than a certain amount. Furthermore, if a time delay is given to the release and operation of the parking brake, it is possible to give the operator a sense of operation in the hydraulic system.

  The control mode determination unit 56 causes the free fall control unit 60 to perform free fall control when the current operation state satisfies the free fall start condition (YES in any of steps S1 to S3), and otherwise ( In at least one of steps S1 to S3, the normal control unit 58 performs normal control (step S4).

  In the normal control, a control signal is input to the inverter 32 of the drive circuit 18 based on the operation on the winding side or the operation on the lowering side given to the operation lever 26 of the winch operation device 22, and the AC motor 16 is driven to wind. The normal control unit 58 performs the normal driving without passing through the step-up / down converter 34. That is, when performing the normal control, the normal control unit 58 turns on the switching element 50 of the steady drive circuit 36 to place the steady drive circuit 36 in an allowable state, and each switching element 46, 48 is kept off. This makes it possible to efficiently perform the normal control while avoiding energy loss due to on / off of the switching elements 46 and 48 in the buck-boost converter 34.

  On the other hand, when performing the free fall control, the free fall control mode determination unit 62 of the free fall control unit 60 is based on the comparison between the actual rotational speed V of the AC motor 16 and a preset rated speed V1. It is determined whether normal free fall control is performed or whether step-down or step-up control is performed. Specifically, the free fall control mode determination unit 62 causes the normal free fall control unit 64 to perform normal free fall control when the rotational speed V is equal to or less than the rated speed V1 (NO in step S5) (step S6). If the rotational speed V exceeds the rated speed V1 (YES in step S5), the step-down control unit 65 or the step-up control unit 66 performs step-down control or step-up control (steps S9 to S11).

  The normal free fall control (step S6) is performed based on the depression operation amount of the brake pedal 28 in the brake operating device 23. Specifically, the normal free fall control unit 64 calculates a braking torque corresponding to the depression operation amount of the brake pedal 28 and performs regenerative current control so that this braking torque can be obtained. The regenerative current control in this normal free fall control is performed exclusively using the inverter 32, and the buck-boost converter 34 is not used. That is, when performing the normal free fall control, the normal free fall control unit 64 turns on the switching element 50 of the steady drive circuit 36 to place the steady drive circuit 36 in an allowable state, as in the normal control. The switching elements 46 and 48 of the step-up / down converter 34 are kept off. This makes it possible to avoid energy loss due to on / off of the switching elements 46 and 48 in the step-up / down converter 34 and to efficiently perform free fall control other than the step-down control and step-up control.

  If the rotational speed V exceeds the rated speed V1 (YES in step S5), and if the rotational speed V is less than or equal to the maximum allowable speed V2 (> V1) (YES in step S7), the free fall control The mode determination unit 62 determines whether to perform step-down control or step-up control depending on whether or not the brake pedal 28 is depressed (step S8). Specifically, the free fall control mode determination unit 62 determines that the step-down control unit 62 is depressed when the brake pedal 28 is depressed (YES in step S8), that is, when it is determined that the operator intends to brake the electric winch. When the step-down control is performed at 65 (step S9) and the stepping operation is not performed (NO at step S8), that is, when it is determined that the operator does not intend to brake the electric winch, the step-up control unit 66 is subjected to the step-up control. (Step S10).

  In step S9, the step-down control unit 65 performs the following step-down control operation.

  a) The switching element 50 of the steady drive circuit 36 is turned off to put the steady drive circuit 36 in a blocking state.

  b) The step-up / step-down converter 34 is caused to perform a step-down operation by keeping the step-up / step-down converter 34 of the step-up / step-down converter 34 OFF while turning the step-down switching element 42 ON / OFF.

  c) A braking force (braking torque) corresponding to the amount of depression of the brake pedal 28, a regenerative current and a regenerative voltage corresponding thereto, and a duty of turning on the step-down switching element 44 for obtaining the regenerative voltage The ratio is determined, and the step-down switching element 42 is turned on / off based on the duty ratio. Specifically, a larger duty ratio (ON duty ratio of the switching element 44) is set as the depression amount of the brake pedal 28 is larger, that is, as the designated braking force is larger. That is, the degree of pressure reduction is reduced.

  Thus, in the regenerative control (braking control) using the function as the step-down circuit of the step-up / down converter 34, the AC motor 16 is rotating at a speed higher than the rated speed V1, and the battery-side terminal voltage of the inverter 32 is Despite being high, it is possible to perform braking and storage of regenerative power (charging of the battery 30) in accordance with the operator's intention while suppressing the voltage between the terminals of the battery 30 within an allowable range. That is, in the free fall operation, since the suspended load 4 descends at a speed close to the speed of the free fall, there is a possibility that the speed at which the AC motor 16 rotates is extremely high as compared with a normal lowering operation. In this case, the regenerative voltage generated by the AC motor 16 greatly exceeds the maximum voltage of the battery of the normal specification. However, the regenerative operation using the step-down circuit makes it possible to recover the regenerative power while appropriately reducing the voltage input from the inverter 32 to the battery 30 to effectively protect the battery 30 and the like.

  On the other hand, in step S10, the boost control unit 66 performs the next boost control operation.

  a) The switching element 50 of the steady drive circuit 36 is turned off to put the steady drive circuit 36 in a blocking state.

  b) The step-up / down converter 34 is caused to perform a step-up operation by keeping the step-down switching element 42 of the step-up / step-down converter 34 OFF while turning the step-up switching element 44 ON / OFF.

  c) The voltage of the inverter 32 necessary for rotating the AC motor 16 at a speed equal to the rotational speed V (that is, not applying a braking force to the AC motor 16) against the rotational speed V of the AC motor 16 by the free fall operation. And the ON duty ratio of the boosting switching element 44 necessary for boosting by an amount corresponding to the difference between this voltage and the maximum voltage of the battery 30 is determined, and the boosting switching element is determined by this duty ratio. 44 is turned on and off. Specifically, a larger duty ratio (an on-duty ratio of the boosting switching element 44) is set as the rotational speed V is higher. That is, the degree of pressure increase is increased.

  This step-up control is based on the braking force resulting from the regenerative current flowing into the battery 30 from the AC motor 16 via the inverter 32 even though the AC motor 16 is rotating at a speed higher than the rated speed V1. Can be prevented or suppressed, and this makes it possible to ensure the rotational speed V in accordance with the operator's intention not to apply braking.

  On the other hand, when the rotational speed V exceeds the maximum allowable speed V2 (NO in step S7), the free fall control mode determination unit 62 performs forced step-down control on the step-down control unit 65 regardless of the depression operation of the brake pedal 28. (Step S11). In this forced step-down control, the rotational speed V of the AC motor 16 is excessively increased by the free fall operation to prevent the AC motor 16 and other components from being damaged. Is a control for applying braking to the AC motor 16. Therefore, in this forced step-down control, it is preferable to set a high duty ratio (on duty ratio of the step-down switching element 42) for obtaining a large braking torque.

  As described above, the free fall control operation in steps S5 to S11 is continued, but the control mode determination unit 56 satisfies the free fall stop condition set in advance in the operation state during the free fall control operation. If it is determined that it is satisfied (YES in step S12), the free fall control is canceled and the control mode is switched to the normal control (step S4). The free fall stop condition can be set based on the same concept as the setting of the free fall start condition. For example, the following conditions are set.

  1) The rotational speed V of the AC motor 16 has decreased to a preset minimum speed V0 (for example, 1% of the rated speed V1) or less.

  2) The free fall permission switch 24 is turned on (free fall permission) (corresponding to step S1).

  3) The brake pedal 28 of the brake operating device 23 is fully operated, that is, the brake pedal 28 is depressed to the deepest position (corresponding to step S2).

  4) The parking brake provided for the winch drum 10 is activated (corresponding to step 3).

  The present invention is not limited to the embodiments described above, and can take the following forms, for example.

  1) The booster circuit can be omitted as appropriate. For example, instead of the step-up / step-down converter 34 according to the above embodiment, a step-down dedicated converter may be included in the drive circuit 18.

  2) Specific configurations of the inverter, the step-down circuit, and the step-up circuit according to the present invention are not limited to those shown in the embodiment. As these circuits, those conventionally known and having equivalent functions can be applied. Also, the specific configuration of the steady drive circuit is not limited as long as it can be switched between the allowable state and the blocking state.

  3) The direct current power source according to the present invention is not limited to the battery 30. The DC power source may be, for example, a generator directly connected to the engine or a combination of a system power source distributed from a power plant and an A / D converter. In this case, the generated regenerative power may be used in the premises or for power supply to a load connected to the generator or the system power supply.

  4) The step-down determination speed and the step-up determination speed according to the present invention are not necessarily limited to the rated speed V1. Further, a difference may be given between the step-down determination speed and the step-up determination speed. For example, the step-down determination speed of both determination speeds may be set to a speed lower than the rated speed V1.

  5) In the present invention, in order to prevent the introduction of excessive regenerative power to the battery more reliably, it does not prevent the power consumption resistor from being connected in parallel with the battery or the capacitor. In this case, a switching element for turning on / off the introduction of current into the resistor may be provided in series with the resistor.

10 Winch Drum 16 AC Motor 18 Drive Circuit 20 Controller 23 Brake Actuator 28 Brake Pedal 30 Battery (DC Power Supply)
32 Inverter 34 Buck-boost converter (Buck circuit and Boost circuit)
36 steady drive circuit 50 switching element 52 diode 60 free fall control unit 62 free fall control mode determination unit 64 normal free fall control unit 65 step-down control unit 66 step-up control unit

Claims (6)

An apparatus for driving an electric winch,
An AC electric motor connected to the winch drum of the electric winch and rotating the winch drum and capable of generating regenerative electric power accompanying the rotation of the winch drum;
A DC power supply for supplying power for driving the AC motor;
An inverter interposed between the DC power source and the AC motor;
A step-down circuit for lowering a voltage applied to the DC power supply from a voltage generated in the inverter when the AC motor is rotated in the winding direction;
A steady-state drive circuit that is provided in parallel with the step-down circuit and can be switched between an allowable state that allows the current to flow from the inverter to the DC power supply and bypass state that bypasses the step-down circuit;
A free fall control unit that controls the drive of the AC motor, and the free fall control unit has a rotational speed in the lowering direction of the AC motor that exceeds a preset step-down determination speed and brakes the winch drum When the instruction is given, the steady state drive circuit is put into the blocking state and the step-down circuit is operated to generate regenerative power, and the rotational speed in the winding direction of the AC motor is reduced. An electric winch drive device that stops the step-down circuit and puts the steady state drive circuit in the allowable state when the speed is lower than the determination speed.   The drive device for an electric winch according to claim 1, wherein a braking operation device operated to instruct the magnitude of the braking force is provided as means for giving the braking instruction to the braking free fall control unit. The drive device for an electric winch, further comprising: the free fall control unit performing the step-down control so that the degree of step-down by the step-down circuit decreases as the braking force instructed by the brake operation unit increases.   3. The electric winch drive device according to claim 1, wherein the drive device is interposed between the DC power supply and the inverter and is provided in parallel with the steady drive circuit, and a voltage applied to the inverter from the DC power supply is provided. And further comprising a booster circuit that raises the voltage of the DC power supply, wherein the free fall control unit has a rotation speed in the lowering direction of the AC motor exceeding a preset boost determination speed, and instructs to brake the winch drum A drive device for an electric winch that performs boost control by putting the steady drive circuit in the blocking state and operating the boost circuit when the value is not given.   4. The electric winch drive device according to claim 3, wherein the free fall control unit performs the step-up control so that the degree of step-up by the step-up circuit increases as the rotational speed of the AC electric motor increases. Drive device.   5. The electric winch drive device according to claim 3, wherein the free fall control unit is configured such that a rotational speed of the AC motor is a preset maximum allowable speed, and is based on the step-down determination speed and the step-up determination speed. A drive device for an electric winch that forcibly causes the step-down circuit to perform a step-down operation regardless of the presence or absence of the braking instruction when a higher speed is exceeded.   The electric winch drive device according to any one of claims 1 to 5, wherein the steady drive circuit is provided in a path connecting the DC power supply and the inverter, and is disconnected from a state in which the path is conducted. A driving device for an electric winch, comprising: a switching element that can be switched to a state; and a diode that is provided in parallel with the switching element and that allows only a current to flow from the DC power source to the inverter.

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