JP6324661B2 - Excavator - Google Patents

Description

  The present invention relates to an excavator that charges a battery with regenerative power.

  Generally, a hybrid excavator includes an upper swing body mounted with working elements such as a boom, an arm, and a bucket, and drives the boom and arm while rotating the upper swing body to move the bucket to a target work position. To do.

  There has been proposed a hybrid excavator that uses an electric motor as a power source of a turning mechanism for turning the upper turning body and drives the turning mechanism with the electric motor to accelerate and turn the upper turning body (for example, Patent Document 1). reference.). When decelerating the upper swing body, the electric motor functions as a generator to generate electric power, and the obtained regenerative power is stored in the capacitor.

JP 2007-210803 A

  In a hybrid excavator, if a large amount of regenerative power is generated and supplied to a battery, it becomes an overvoltage, which may exceed the upper limit value and the battery may be overcharged. When the battery is overcharged, it enters an overvoltage state, and the deterioration of the battery is promoted. For this reason, the lifetime of the battery is shortened.

  Therefore, an object of the present invention is to provide an excavator that prevents overcharge of a capacitor even when large regenerative power is generated.

In order to achieve the above-described object, an excavator according to an embodiment of the present invention includes a lower traveling body, an upper swinging body that is pivotably attached to the lower traveling body, and a turning electric motor that rotates the upper swinging body. A power storage device for accumulating regenerative energy of the turning electric motor, an attachment attached to the upper turning body, a posture detecting unit for detecting posture information of the attachment, and a control device , the control device comprising: Based on the attitude information, the inertia moment of the upper swing body is calculated, and the storage target value of the battery is variably controlled in response to the change of the inertia moment .

  ADVANTAGE OF THE INVENTION According to this invention, even if big regenerative electric power generate | occur | produces, the shovel which prevents the overcharge of a capacitor | condenser can be provided.

It is a side view of a hybrid type shovel. It is a block diagram which shows the structure of the drive system of the hybrid type shovel of FIG. It is a block diagram which shows the structure of an electrical storage system. It is a circuit diagram of a power storage system. It is a flowchart of the process which sets the target value of SOC. It is a flowchart of the process which calculates a regeneration expected target value. It is a figure for demonstrating the process which sets SOC target value in excavation and loading operation | work. It is a block diagram (the 1) which shows the structure of the drive system of a series type hybrid type shovel. It is a block diagram (the 2) which shows the structure of the drive system of a series type hybrid type shovel.

  FIG. 1 is a side view showing a hybrid excavator to which the present invention is applied.

  An upper swing body 3 is mounted on the lower traveling body 1 of the hybrid excavator via a swing mechanism 2. A boom 4 is attached to the upper swing body 3. An arm 5 is attached to the tip of the boom 4, and a bucket 6 is attached to the tip of the arm 5. The boom 4, the arm 5, and the bucket 6 constitute an excavation attachment that is an example of an attachment, and are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9. The upper swing body 3 is provided with a cabin 10 and is mounted with a power source such as an engine.

  FIG. 2 is a block diagram showing the configuration of the drive system of the hybrid excavator according to the embodiment of the present invention. In FIG. 2, the mechanical power system is indicated by a double line, the high-pressure hydraulic line is indicated by a thick solid line, the pilot line is indicated by a broken line, and the electric drive / control system is indicated by a thin solid line.

  An engine 11 as a mechanical drive unit and a motor generator 12 as an assist drive unit are respectively connected to two input shafts of a transmission 13. A main pump 14 and a pilot pump 15 are connected to the output shaft of the transmission 13 as hydraulic pumps. A control valve 17 is connected to the main pump 14 via a high pressure hydraulic line 16.

  The control valve 17 is a control device that controls a hydraulic system in the hybrid excavator. The hydraulic motors 1A (for right) and 1B (for left), the boom cylinder 7, the arm cylinder 8, and the bucket cylinder 9 for the lower traveling body 1 are connected to the control valve 17 via a high-pressure hydraulic line.

  A power storage system 120 including a capacitor as a capacitor is connected to the motor generator 12 via an inverter 18 as a motor generator controller. The power storage system 120 is connected to a turning electric motor 21 as an electric working element via an inverter 20 as a motor generator control unit. A resolver 22, a mechanical brake 23, and a turning transmission 24 are connected to the rotating shaft 21 </ b> A of the turning electric motor 21. An operation device 26 is connected to the pilot pump 15 through a pilot line 25. The turning electric motor 21, the inverter 20, the resolver 22, the mechanical brake 23, and the turning transmission 24 constitute a load drive system.

  The operating device 26 includes a lever 26A, a lever 26B, and a pedal 26C. The lever 26A, the lever 26B, and the pedal 26C are connected to the control valve 17 and the pressure sensor 29 via hydraulic lines 27 and 28, respectively. The pressure sensor 29 is connected to a controller 30 that performs drive control of the electric system.

In the present embodiment, a posture detection unit for detecting the posture of the attachment is attached to the shovel. Specifically, a boom angle sensor 7B for detecting the angle of the boom 4 is attached to the support shaft of the boom 4, and an arm angle sensor 7A for detecting the angle of the arm 5 is attached to the support shaft of the arm 5. ing. A bucket angle sensor (not shown) for detecting the angle of the bucket 6 may be attached to the support shaft of the bucket 6. The arm angle sensor 7A and the boom angle sensor 7B as posture detecting units supply the detected arm angle θ _A and boom angle θ _B to the controller 30, respectively.

  FIG. 3 is a block diagram showing the configuration of the power storage system 120. Power storage system 120 includes a capacitor 19 as a power storage device, a step-up / down converter 100, and a DC bus 110. The DC bus 110 serving as the second capacitor controls the power transfer between the capacitor 19 serving as the first capacitor, the motor generator 12, and the turning motor 21. The capacitor 19 is provided with a capacitor voltage detector 112 for detecting a capacitor voltage value and a capacitor current detector 113 for detecting a capacitor current value. The capacitor voltage value and the capacitor current value detected by the capacitor voltage detection unit 112 and the capacitor current detection unit 113 are supplied to the controller 30.

  The step-up / step-down converter 100 performs control to switch between the step-up operation and the step-down operation so that the DC bus voltage value falls within a certain range according to the operating state of the motor generator 12 and the turning electric motor 21. The DC bus 110 is disposed between the inverters 18 and 20 and the step-up / down converter 100, and transfers power between the capacitor 19, the motor generator 12, and the turning electric motor 21.

  Returning to FIG. 2, the controller 30 is a control device as a main control unit that performs drive control of the hybrid excavator. The controller 30 is configured by an arithmetic processing unit including a CPU (Central Processing Unit) and an internal memory, and is realized by the CPU executing a drive control program stored in the internal memory.

  The controller 30 converts the signal supplied from the pressure sensor 29 into a speed command, and performs drive control of the turning electric motor 21. The signal supplied from the pressure sensor 29 corresponds to a signal indicating an operation amount when the operation device 26 is operated to turn the turning mechanism 2.

  The controller 30 performs operation control of the motor generator 12 (switching between electric (assist) operation or power generation operation) and charge / discharge control of the capacitor 19 by drivingly controlling the buck-boost converter 100 as a buck-boost controller. Do. The controller 30 is a step-up / down converter based on the charged state of the capacitor 19, the operating state of the motor generator 12 (electric (assist) operation or generating operation), and the operating state of the turning motor 21 (power running operation or regenerative operation). Switching control between 100 step-up operations and step-down operations is performed, and thereby charge / discharge control of the capacitor 19 is performed.

  The switching control between the step-up / step-down operation of the step-up / step-down converter 100 is performed by controlling the DC bus voltage value detected by the DC bus voltage detection unit 111, the capacitor voltage value detected by the capacitor voltage detection unit 112, and the capacitor current detection unit 113. Is performed based on the capacitor current value detected by.

  In the configuration as described above, the electric power generated by the motor generator 12 as an assist motor is supplied to the DC bus 110 of the power storage system 120 via the inverter 18 and supplied to the capacitor 19 via the step-up / down converter 100. . The regenerative power generated by the regenerative operation of the turning electric motor 21 is supplied to the DC bus 110 of the power storage system 120 via the inverter 20 and supplied to the capacitor 19 via the step-up / down converter 100.

The rotational speed (angular speed ω) of the turning electric motor 21 is detected by a resolver 22 as a rotational speed detection unit. The angle of the arm 5 (arm angle θ _A ) is detected by an arm angle sensor 7 A such as a rotary encoder provided on the support shaft of the arm 5, and the angle of the boom 4 (boom angle θ _B ) is determined by the support shaft of the boom 4. Is detected by a boom angle sensor 7B such as a rotary encoder provided in The controller 30 obtains an estimated turning regenerative power (energy) by calculation based on the angular velocity ω, the arm angle θ _A , and the boom angle θ _B of the turning electric motor 21. Note that if a bucket angle sensor is present, the controller 30 may additionally consider the bucket angle. Then, the controller 30 obtains a predicted regeneration target value of the SOC by calculation based on the estimated turning regenerative power obtained by calculation. The controller 30 controls each part of the hybrid excavator so as to bring the SOC of the capacitor 19 close to the calculated expected regeneration target value. Details of the calculation of the estimated turning regenerative power (energy) and the expected regeneration target value will be described later.

  FIG. 4 is a circuit diagram of the power storage system 120. The step-up / down converter 100 includes a reactor 101, a boosting IGBT (Insulated Gate Bipolar Transistor) 102A, a step-down IGBT 102B, a power connection terminal 104 for connecting the capacitor 19, an output terminal 106 for connecting inverters 18 and 20, and And a smoothing capacitor 107 inserted in parallel with the pair of output terminals 106. The output terminal 106 of the buck-boost converter 100 and the inverters 18 and 20 are connected by a DC bus 110.

  One end of the reactor 101 is connected to an intermediate point between the step-up IGBT 102 </ b> A and the step-down IGBT 102 </ b> B, and the other end is connected to the power supply connection terminal 104. Reactor 101 is provided in order to supply induced electromotive force generated when boosting IGBT 102 </ b> A is turned on / off to DC bus 110.

  The step-up IGBT 102 </ b> A and the step-down IGBT 102 </ b> B are semiconductor elements that are configured by a bipolar transistor in which a MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is incorporated in a gate portion and can perform high-power high-speed switching. The step-up IGBT 102A and the step-down IGBT 102B are driven by the controller 30 by applying a PWM voltage to the gate terminal. Diodes 102a and 102b, which are rectifier elements, are connected in parallel to the step-up IGBT 102A and the step-down IGBT 102B.

  Capacitor 19 may be a chargeable / dischargeable capacitor so that power can be exchanged with DC bus 110 via buck-boost converter 100. 4 shows a capacitor 19 as a capacitor. Instead of the capacitor 19, a secondary battery capable of charging / discharging such as a lithium ion battery, a lithium ion capacitor, or other forms capable of transmitting and receiving power. A power supply may be used as a capacitor.

  The power connection terminal 104 and the output terminal 106 may be terminals that can connect the capacitor 19 and the inverters 18 and 20. A capacitor voltage detection unit 112 that detects a capacitor voltage is connected between the pair of power supply connection terminals 104. A DC bus voltage detector 111 that detects a DC bus voltage is connected between the pair of output terminals 106.

  The capacitor voltage detector 112 detects the voltage value (vbat_det) of the capacitor 19. The DC bus voltage detection unit 111 detects the voltage of the DC bus 110 (hereinafter, DC bus voltage: vdc_det). The smoothing capacitor 107 is a power storage element that is inserted between the positive terminal and the negative terminal of the output terminal 106 and smoothes the DC bus voltage. The smoothing capacitor 107 maintains the voltage of the DC bus 110 at a predetermined voltage. The capacitor current detection unit 113 is detection means for detecting the value of the current flowing through the capacitor 19 and includes a resistor for current detection. That is, the capacitor current detection unit 113 detects the current value (ibat_det) flowing through the capacitor 19.

  In the buck-boost converter 100, when boosting the DC bus 110, a PWM voltage is applied to the gate terminal of the boosting IGBT 102A, and the boosting IGBT 102A is turned on / off via the diode 102b connected in parallel to the step-down IGBT 102B. The induced electromotive force generated in the reactor 101 when the power is turned off is supplied to the DC bus 110. Thereby, the DC bus 110 is boosted.

  When the DC bus 110 is stepped down, a PWM voltage is applied to the gate terminal of the step-down IGBT 102B, and regenerative power supplied via the step-down IGBT 102B is supplied from the DC bus 110 to the capacitor 19. As a result, the electric power stored in the DC bus 110 is charged in the capacitor 19 and the DC bus 110 is stepped down.

  In practice, a drive unit that generates a PWM signal for driving the boosting IGBT 102A and the step-down IGBT 102B exists between the controller 30 and the step-up IGBT 102A and the step-down IGBT 102B, but is omitted in FIG. Such a driving unit can be realized by either an electronic circuit or an arithmetic processing unit.

  In the hybrid excavator having the above-described configuration, the electrical load can be driven in an energy efficient state with the electric power from the battery by maintaining the state of charge (SOC) of the capacitor 19 at a high level.

  In the conventional hybrid excavator, the target SOC of the capacitor is set small so that the capacitor is not overcharged even when large regenerative power is generated from an electric load or the like and supplied to the capacitor. That is, even if a large amount of electric power is supplied to the battery due to unexpected power generation or regeneration, the target SOC is set to 70%, for example, with a margin so that the SOC does not become 100% even if it is absorbed. As a result, the SOC of the battery is always controlled to be 70% or less, and the output voltage of the battery is a low voltage corresponding to an SOC of 70% or less.

  Here, if the target SOC of the battery is set to a higher value than before, the output voltage of the battery also increases, and the electric load can be driven efficiently. That is, by increasing the output voltage of the battery and driving the electric load with a higher voltage than before, the electric load can be driven more efficiently than before.

  Further, in the case of using a capacitor with a small storage capacity in order to reduce the size of the capacitor and reduce the cost of the storage system, as much power as possible can be held in the capacitor by setting the target SOC of the capacitor high. For example, when a capacitor is used as the capacitor, the capacitor can be made smaller without reducing the conventional amount of electricity stored by using a small capacitor and setting the target SOC high.

  Here, in consideration of the normal operation state of the drive unit in the drive system of the hybrid excavator and the charge amount and the charge rate (SOC) of the capacitor, there is no problem in normal use if the SOC of the capacitor is 90% or less. I understood it. Therefore, by setting the target SOC of the capacitor to 90%, the electric load can be efficiently driven at a high voltage, and the capacitor can be reduced in size and cost.

  However, when the target SOC of the battery is set to a high value such as 90%, for example, if a large regenerative power is generated in a state where the SOC of the battery is high, there is a risk of overcharging. Therefore, in the embodiment described below, the charge rate (SOC) of the battery (capacitor) is variably controlled. That is, when it is predicted that large regenerative power is generated, the SOC is controlled in advance so that the SOC does not exceed the upper limit value of the system even if the regenerative power is absorbed.

  Next, a method for controlling the charging rate (SOC) of the capacitor 19 in the hybrid excavator of FIG. 1 will be described.

  In the present embodiment, when the upper swing body 3 is decelerated, the turning electric motor 21 functions as a generator, generates regenerative power (swing regenerative power), and supplies it to the power storage system 120.

  Further, in this embodiment, by using the SOC of the capacitor 19 as a capacitor in a region as high as possible, the amount of charge is always increased to maintain the discharge voltage of the capacitor 19 at a high level, thereby preventing power shortage. However, the capacitor 19 is discharged at a high voltage to increase energy efficiency. At this time, if a large amount of regenerative power is generated and supplied to the capacitor 19, since a larger amount of power is charged with a high SOC, the capacitor 19 is overpowered.

  Therefore, in the present embodiment, it is predicted in advance that turning regenerative power is generated, and in such a case, the SOC of the capacitor 19 is lowered to suppress the capacitor 19 from being overcharged. That is, the estimated value of the regenerative power is calculated, and the target value of the SOC is determined and changed based on the estimated regenerative power (estimated regenerative energy). Normally, the target value of SOC is set to a constant value based on the control conditions of the system. However, in this embodiment, the target value of SOC is estimated swirl regenerative power (estimated swirl) that is predicted to be generated from now on. It is changed at any time based on the regenerative energy.

  FIG. 5 is a flowchart of a process for setting the SOC target value. First, in step S1, an estimated turning regenerative power QA is calculated.

  Subsequently, in step S2, it is determined whether or not the estimated turning regenerative power QA is greater than zero. That is, it is determined whether or not there is an estimated turning regenerative power QA. If the estimated turning regenerative power QA is zero, that is, if turning is not performed and it is estimated that no regenerative power is generated, the process proceeds to step S3. In step S3, the SOC target value SOCtg as the power storage target value is set to the system control upper limit SOCcul, and the current process is terminated. The system control upper limit value SOCcul is an upper limit value of the SOC determined by the control of the hybrid excavator. When the detected value of the SOC exceeds the system control upper limit value SOCcul, it is determined that the capacitor 19 has overflowed.

  On the other hand, when the estimated turning regenerative power QA is greater than zero, that is, when it is estimated that regenerative power is generated, the process proceeds to step S4. In step S4, the expected regeneration target value SOCetg is calculated based on the calculated estimated turning regenerative power QA. The expected regeneration target value SOCetg is an SOC value such that the SOC of the capacitor 19 does not become larger than the above-described system control upper limit SOCcul even when the estimated turning regenerative power QA is supplied to the capacitor 19, and is greater than the system control upper limit SOCcul. Small value.

  When the estimated regeneration target value SOCetg is calculated in step S4, the process proceeds to step S5. In step S5, the SOC target value SOCtg as the power storage target value is set to the regeneration expected target value SOCetg, and the current process is terminated. The expected regeneration target value SOCetg is a value that changes according to the value of the estimated turning regenerative power QA, and the SOC target value SOCtg also changes according to the value of the estimated turning regenerative power QA.

  Note that the processing in step S3 and the processing in step S5 described above are performed by the power storage target value control unit 301 of the controller 30.

  Next, the calculation process of the estimated turning regenerative power QA in step S1 described above will be described. Calculation of the estimated turning regenerative power QA is performed by the estimated regenerative energy calculation unit 302 of the controller 30. The calculation of the estimated turning regenerative power QA is performed based on the following equation representing the kinetic energy of an object that performs rotational motion.

QA = 1/2 × J × ω ²
Here, J is the moment of inertia of the upper swing body 3, and ω is the angular velocity of the swing motion of the upper swing body 3. The angular velocity ω can be obtained from the rotational speed of the turning electric motor 21 detected by the resolver 22.

  The inertia moment J is a value that changes according to the posture of the attachment including the boom 4 and the arm 5, and is calculated by the inertia moment calculation unit 303 of the controller 30.

Specifically, the inertia moment calculation unit 303 calculates the inertia moment J of the upper swing body 3 based on the arm angle θ _A and the boom angle θ _B output by the arm angle sensor 7A and the boom angle sensor 7B as the posture detection unit. calculate. When the bucket angle sensor as the posture detection unit is provided, the moment of inertia calculation unit 303 is configured so that the inertia of the upper swing body 3 is based on the arm angle θ _A , the boom angle θ _B, and the bucket angle output from the bucket angle sensor. The moment J may be calculated.

  Next, the process of step S4 in FIG. 5 will be described. The process of step S4 is a process for calculating the expected regeneration target value SOCetg. The expected regeneration target value SOCetg is performed by the power storage target value determination unit 304 of the controller 30. FIG. 6 is a flowchart of a process for calculating the regenerative expected target value SOCetg. First, in step S11, a storage work amount Qmax that is electric power stored in the capacitor 19 when the charging rate (SOC) of the capacitor 19 reaches the system control upper limit SOCcul is calculated. The stored power work Qmax corresponds to the maximum power that can be stored in the capacitor 19 in terms of system control. When a capacitor is used, the stored energy work Qmax can be calculated using the following equation.

Qmax = 1/2 × C × V ² = 1/2 × C × (360 × √SOCcul) ²
Here, C is the capacitance of the capacitor 19.

  Next, in step S12, a target value Q of power that can be stored in the capacitor 19 is calculated by subtracting the estimated turning regenerative power QA from the stored work amount Qmax (Q = Qmax−QA).

  Then, in step S13, the expected regeneration target value SOCetg is obtained from the target value Q of power. The expected regeneration target value SOCetg can be calculated by the following equation.

SOCetg = 2 × Q / (C × 360 ² )
When the expected regeneration target value SOCetg is calculated as described above, the SOC target value SOCtg is set to the expected regeneration target value SOCetg in step S5 shown in FIG.

  Here, the setting of the SOC target value SOCtg in excavation / loading work performed by the hybrid excavator will be described. FIG. 7 is a diagram for explaining processing for setting the SOC target value SOCtg in excavation / loading work. Transitions indicated by solid lines in FIG. 7 indicate the turning speed W, the estimated turning regenerative power QA, and the SOC target value SOCtg. Represents the transition. Note that, during the operation from time t0 to time t4 in FIG. 7, the estimated turning regenerative power QA can be expected, and therefore, the regenerative expected target value SOCetg is set to the SOC target value SOCtg as the power storage target value. In addition, the transition shown by the dotted line in FIG. 7 is the comparison target when the moment of inertia J of the upper swing body 3 does not change during the excavation / loading operation, that is, when the attachment posture (turning radius) does not change. Represent.

  In the excavation / loading work, the turning speed W of the upper swing body 3 is proportional to the angular speed ω of the turning electric motor 21 and changes as indicated by F7A in the excavation / loading work.

Further, the estimated turning regenerative power QA is calculated by multiplying the value obtained by squaring the angular velocity ω of the turning electric motor 21 by the moment of inertia J (QA = 1/2 × J × ω ² ), as described above. Transition as shown. Here, after the time when the turning speed W reaches a peak, the turning speed is decelerated, and thus turning regenerative power is generated. Since the minus direction (negative value) of the turning speed W means reverse rotation, the estimated turning regenerative power QA is calculated by the absolute value of the turning speed W.

  Here, in a general excavation / loading operation, in the case of lifting and turning, since the boom 4 is raised and the arm 5 is closed and the turning radius of the excavation attachment is reduced, the moment of inertia J is also reduced. For this reason, the estimated turning regenerative power QA (solid line) in the present embodiment is smaller than the case (dotted line) assuming that the orientation of the attachment does not change if the turning speed W (angular speed ω) is the same. . On the other hand, in the case of the swivel turning, the boom 4 is lowered and the arm 5 is opened to increase the turning radius of the excavation attachment, so that the moment of inertia J is also increased. Therefore, the estimated turning regenerative power QA (solid line) in the present embodiment is larger than the case (dotted line) on the assumption that the posture of the attachment does not change if the turning speed W (angular speed ω) is the same. .

  Then, the estimated regeneration target value SOCetg becomes the maximum charging rate (system control upper limit value SOCcul) of the capacitor 19 allowed in system control when the estimated turning regenerative power QA is supplied to the capacitor 19 and charged. Set to the correct value. Therefore, the expected regeneration target value SOCetg is a value obtained by subtracting the estimated turning regenerative power QA from the system control upper limit value SOCcul, that is, the estimated turning regenerative power QA is inverted and zero is adjusted to the system control upper limit value SOCcul, and F7C It becomes a pattern as shown in.

  Thus, the controller 30 calculates the estimated turning regenerative power QA and the expected regeneration target value SOCetg based on the moment of inertia J calculated in real time. Therefore, the controller 30 appropriately calculates the estimated turning regenerative power QA and the expected regeneration target value SOCetg in a state where the inertia moment J during the lifting turn is relatively small, a state where the inertia moment J during the lifting turn is relatively large, and the like. Can be reflected. As a result, as can be seen from the comparison with the transition indicated by the dotted line, the controller 30 has a more appropriate charge rate (SOC) of the capacitor 19 than when calculating the estimated turning regenerative power QA while keeping the moment of inertia J at a constant value. Can be controlled.

  Here, in F7C, the case where the stored voltage value of the capacitor 19 at time t = t0 is 100% with respect to the rated voltage will be described. From time t0 to t10, a turning operation is performed. Therefore, the SOC target value SOCtg (in this case, the expected regeneration target value SOCetg) is lowered in accordance with the increase in the calculated estimated turning regenerative power QA. Since the expected regeneration target value SOCetg is lowered, the electric power that has been stored (charged) up to the system control upper limit SOCcul is discharged by a decrease in the expected regeneration target value SOCetg. The electric power discharged at this time can be used for powering operation of raising the boom 4 or turning.

  Moreover, since the turning speed W decreases at the time t10 to t2, the calculated estimated turning regenerative power QA also decreases. Accordingly, SOC target value SOCtg (in this case, expected regeneration target value SOCetg) increases. At the same time, turning regenerative electric power is generated because the turning electric motor 21 is braked (decelerated), and the turning regenerative electric power can be charged to the capacitor 19 by an increase in the expected regeneration target value SOCetg.

  Similarly, from time t3 to t11, the expected regeneration target value SOCetg decreases, and discharging is performed by the amount corresponding to the decrease in the expected regeneration target value SOCetg. Further, at times t11 to t4, the expected regeneration target value SOCetg is increased, and charging is performed by the increase in the estimated regeneration target value SOCetg.

  Note that, as indicated by the dotted line, the expected regeneration target value SOCetg when it is assumed that the attachment posture (turning radius) does not change is slightly smaller than the system control upper limit SOCcul at time t3 to t4. Don't be. Under these conditions, if the attachment is extended (the turning radius is large), the attachment posture (turning radius) is different from the premise, and the actual turning regenerative power exceeds the estimated value. The revolving regenerative power is charged into the capacitor 19. In this case, the charging rate (SOC) of the capacitor 19 not only becomes higher than the expected regeneration target value SOCetg, but may exceed the system control upper limit SOCcul. However, in the present embodiment, the controller 30 can sufficiently reduce the expected regeneration target value SOCetg, as indicated by the solid line. Therefore, even when a large turning regenerative electric power is charged to capacitor 19, it is possible to prevent the charging rate (SOC) of capacitor 19 from exceeding system control upper limit SOCcul.

Here, the capacitance of the capacitor 19 C, when the stored voltage (inter-terminal voltage) is V, the power storage energy E which is charged in the capacitor 19 is expressed by E = (1/2) CV ^2. Therefore, if the storage voltage V is increased, the capacity of the capacitor 19 for maintaining the same energy can be reduced. For example, conventionally, in order to prevent the SOC from exceeding the system control upper limit SOCcul, the SOC target value SOCtg is determined with sufficient consideration of regenerative power. That is, the conventional SOC target value SOCtg is, for example, 67% (= V / Vmax: charging voltage) with respect to the rated voltage (Vmax) so that large regenerative power can be absorbed. Ratio). When SOC target value SOCtg is set to system control upper limit value SOCcul, capacitor 19 is charged so that the charging voltage is 100% (= V / Vmax: charging voltage ratio) with respect to the rated voltage.

By the way, if the charging voltage value V stored in the capacitor 19 is increased by √2 times as represented by E = (1/2) CV ² , the same stored energy E is obtained even if the capacitance is halved. Can be obtained. In other words, if the charging voltage value V is increased by √2 times, the capacitance of the capacitor can be reduced to ½.

Specifically, in the past, control was performed using an SOC with a charging voltage ratio of 67%, but by setting the charging voltage ratio to 95%, which is a charging voltage ratio when √2 times, The capacity of the capacitor 19 can be halved while maintaining the same stored energy. That is, by setting the charging voltage ratio to 95%, a capacitor having a capacitance of 1/2 can be used while maintaining the same stored energy as when the charging voltage ratio is 67%. Here, when the charging voltage ratio is 95%, the SOC is expressed as a ratio of the square of the voltage V, and therefore the SOC is about 90% (SOC = (1/2) CV ² / (1/2 ) CVmax ² ).

  In the present embodiment, the SOC can be controlled to be about 90% (charge voltage ratio 95%) or more in a state where there is no expectation of regenerative power. That is, the capacitor capacity can be halved compared to the conventional case. When regenerative power is expected, SOC is controlled at a high level in a state where there is no expectation of regenerative power by calculating in real time the expected regenerative target value SOCetg while considering the kinetic energy (moment of inertia J) of the electric motor 21 for turning. Even if it does, it is because it can prevent that an overcharge generate | occur | produces in the case of subsequent regenerative operation. Specifically, since the SOC target value is variably controlled in accordance with the change in the kinetic energy (moment of inertia J) of the electric motor 21 for turning, if the regenerative power is expected to be generated, the SOC ratio is reduced in advance. It is because it can be kept. Therefore, applying this embodiment to a hybrid excavator increases the degree of freedom in selecting the capacitor 19.

  As can be seen from F7C, the expected regeneration target value SOCetg obtained in the present embodiment is higher than the target upper limit value of the conventional SOC when it is estimated that no regenerative power is generated (QA = 0). It becomes equal to the control upper limit value SOCcul. Further, the regenerative expected target value SOCetg obtained in the present embodiment is calculated when the regenerative power is estimated to be generated (QA> 0) when the estimated turning regenerative power QA is charged to the capacitor 19 from the system control upper limit SOCcul. This is a value obtained by subtracting the increasing charging rate (SOC) from the system control upper limit SOCcul. As a result, while maintaining the charging rate (SOC) of the capacitor 19 at a value close to the system control upper limit value SOCcul, the charging rate (SOC) of the capacitor 19 becomes equal to the system control upper limit value SOCcul even when regenerative power is supplied to the capacitor 19. It can be controlled so as not to exceed.

  Further, in the above-described embodiment, the estimated turning regenerative electric power QA is obtained in order to calculate the expected regeneration target value SOCetg, but instead of the bucket 6, like a riffmag excavator with a lifting magnet attached to the tip of the arm, When the regenerative function other than the swivel regenerative function has a riffmag regenerative function, or when it has a boom regenerative function, obtain the estimated regenerative power obtained by adding the estimated refumag regenerative power and the estimated boom regenerative power to the estimated revolving regenerative power QA. And it is sufficient. The regenerative power from the lifting magnet is a reverse current that flows when the lifting magnet is turned off, and has a substantially constant current value. Therefore, the estimated riff mug regenerative power can be set as a fixed value. In addition, when the voltage value of the capacitor 19 is smaller than the storage target value from time t0 to t10, the capacitor 19 is charged. Similarly, at time t3 to t11, when the voltage value of the capacitor 19 is smaller than the storage target value, the capacitor 19 is charged.

  Furthermore, when there is no prospect of regeneration, the power storage target value is set to a value equal to the system control upper limit SOCcul. However, when there is no possibility of regeneration, the power storage target value may be set to a value with a margin of several percent from the system control upper limit value SOCcul. Further, the power storage target value may be set in a predetermined range.

  In the above-described embodiment, an example in which the present invention is applied to a so-called parallel type hybrid excavator that drives the main pump by connecting the engine 11 and the motor generator 12 to the main pump 14 that is a hydraulic pump will be described. did. However, in the present invention, the motor generator 12 directly connected to the engine 11 is driven by the engine 11 as shown in FIG. 8, or is connected to the engine 11 via the transmission 13 as shown in FIG. The motor generator 12 is driven by the engine 11, the electric power generated by the motor generator 12 is stored in the power storage system 120, and then the main pump 14 is driven only by the stored electric power via the inverter and the pump motor 400. It can also be applied to series-type hybrid excavators. In this case, the motor generator 12 has a function as a generator that performs only a power generation operation by being driven by the engine 11.

  The present invention is not limited to the specifically disclosed embodiments described above, and various modifications and improvements can be made without departing from the scope of the present invention.

  DESCRIPTION OF SYMBOLS 1 ... Lower traveling body 1A, 1B ... Hydraulic motor 2 ... Turning mechanism 3 ... Upper turning body 4 ... Boom 5 ... Arm 6 ... Bucket 7 ... Boom cylinder 7A ... Arm angle sensor 7B ... Boom angle sensor 8 ... Arm cylinder 9 ... Bucket cylinder 10 ... Cabin 11 ... Engine 12 ... Motor generator 13 ... Transmission 14 ..Main pump 15 ... Pilot pump 16 ... High pressure hydraulic line 17 ... Control valve 18, 20 ... Inverter 19 ... Capacitor 21 ... Rotating motor 22 ... Resolver 23 ...・ Mechanical brake 24 ・ ・ ・ Swivel transmission 25 ・ ・ ・ Pilot line 26 ・ ・ ・ Operating device 26A, 26B ・ ・ ・ Lever 26C ・ ・-Pedal 27 ... Hydraulic line 28 ... Hydraulic line 29 ... Pressure sensor 30 ... Controller 100 ... Buck-boost converter 101 ... Reactor 102A ... Boost IGBT 102B ... Decrease IGBT 104 ... Power supply connection terminal 106 ... Output terminal 107 ... Capacitor 110 ... DC bus 111 ... DC bus voltage detector 112 ... Capacitor voltage detector 113 ... Capacitor current detector DESCRIPTION OF SYMBOLS 120 ... Power storage system 301 ... Power storage target value control part 302 ... Estimated regenerative energy calculation part 303 ... Moment of inertia calculation part 304 ... Power storage target value determination part 400 ... Electric motor for pumps

Claims (5)

A lower traveling body,
An upper swivel body pivotably attached to the lower traveling body;
A turning electric motor for turning the upper turning body;
A battery for accumulating regenerative energy of the electric motor for turning;
An attachment attached to the upper swing body;
A posture detection unit that is disposed on the attachment and detects posture information of the attachment;
A control device,
The control device is configured to change the attachment method that changes during turning detected by the posture detection unit.
Calculating the moment of inertia of the upper swing structure change during turning based on the posture information of the cement,
In response to the change in the moment of inertia, the storage target value of the battery is variably controlled during turning .
Excavator. The attachment includes a boom attached to the upper swing body, and an arm attached to the boom,
The posture detection unit detects an angle of the boom and an angle of the arm;
While the upper swing body is turning, the control device is configured to calculate the upper swing body calculated in real time from the moment of inertia calculated in real time from the angle of the boom and the angle of the arm and the rotation speed of the electric motor for turning. Calculating the estimated turning regenerative energy in real time based on the turning angular velocity of the battery, and calculating the storage target value of the battery in real time based on the estimated turning regenerative energy.
The excavator according to claim 1. The attachment includes a bucket;
The posture detection unit detects an angle of the bucket;
The control device calculates the moment of inertia from the angle of the boom, the angle of the arm, and the angle of the bucket;
The shovel according to claim 2. The estimated turning regenerative energy calculated at the time of lifting and turning is smaller as the turning radius of the attachment is smaller,
The power storage target value calculated at the time of lifting and turning is larger as the turning radius of the attachment is smaller.
The shovel according to claim 2. The estimated turning regenerative energy calculated at the time of holding down turning is smaller as the turning radius of the attachment is larger,
The power storage target value calculated at the time of turning down is smaller as the turning radius of the attachment is larger.
The shovel according to claim 2.

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