JP5425721B2 - Hybrid work machine - Google Patents

Description

  The present invention relates to a hybrid work machine, and more particularly to a hybrid work machine using a capacitor as a capacitor.

  A hybrid work machine that assists an engine that drives a hydraulic pump with an electric motor has been used. The hybrid work machine requires a chargeable / dischargeable battery as a power source for driving the electric motor. As the capacitor, a large-capacity capacitor that can freely discharge and store electricity can be used. A hybrid construction machine using an electric double layer capacitor as a capacitor has been proposed (for example, see Patent Document 1). By using an electric double layer capacitor as a capacitor, efficient charging / discharging becomes possible.

JP 2007-155586 A

  Capacitors deteriorate with long-term use, and their capacitance (the ability to store power) decreases. It is considered that the deterioration of the capacitor is caused by the blockage of the electrode surface. It has been found that the deterioration of the capacitor is accelerated as a high voltage is applied between the terminals or as the ambient temperature becomes higher.

  When a capacitor deteriorates, the amount of power that can be stored in the capacitor decreases, and its internal resistance increases. Therefore, when the capacitor is deteriorated, it is impossible to supply appropriate electric power to the electric load, and there is a possibility that a work such as an operation with the electric load cannot be performed or a work operation is delayed. Moreover, there is a possibility that a problem that the specified force cannot be exhibited in each operation by the electric load may occur. Therefore, there is a demand for development of a technique for easily and accurately judging deterioration of a capacitor.

  According to the present invention, there is provided a hybrid work machine having a hydraulic pump driven by an engine, a motor generator connected to the engine, and a capacitor for supplying electric power to the motor generator, When the motor generator is in a power generation operation, the current charging energy is calculated as the electric power output from the motor generator, and when the current charging energy is supplied to the capacitor based on the initial capacitance of the capacitor There is provided a hybrid work machine that calculates virtual charging energy as electric power stored in a capacitor and compares the current charging energy and the virtual charging energy to determine deterioration of the capacitor.

  In the hybrid work machine described above, it is preferable to determine that the battery has deteriorated when the virtual charging energy is larger than the current charging energy. The current charging energy may be calculated from the output current and output voltage of the motor generator. Alternatively, the current charging energy may be calculated from the output command value of the motor generator. Moreover, it is good also as calculating the said virtual charge energy from the voltage between the terminals of the said electrical storage device.

  According to the present invention, when the motor generator is operated to generate power and the capacitor is charged, the charging energy output from the motor generator and the charging energy calculated from the voltage between the terminals of the capacitor are simply compared. Deterioration can be easily determined.

1 is a side view of a hybrid excavator that is an example of a hybrid work machine to which the present invention is applied. It is a block diagram which shows the structure of the drive system of a hybrid type shovel. It is a block diagram which shows the structure of an electrical storage system. It is a graph which shows the electric power generated at the time of driving a motor generator and generating electric power. It is a graph which shows the change of the voltage between the terminals of a capacitor at the time of charging a capacitor. It is a block diagram which shows the structure of the drive system of the hybrid type shovel which electrifies a turning mechanism and performs boom regeneration. It is a side view of a hybrid type bulldozer. It is a figure which shows the structure of the drive system of a hybrid type bulldozer.

  FIG. 1 is a side view of a hybrid excavator as an example of a hybrid work machine 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 are hydraulically driven by a boom cylinder 7, an arm cylinder 8, and a bucket cylinder 9, respectively. 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 shown in FIG. In FIG. 2, the mechanical power system is indicated by a double line, the high-pressure hydraulic line is indicated by a solid line, the pilot line is indicated by a broken line, and the electric drive / control system is indicated by a 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 turning hydraulic motor 2 </ b> A for driving the turning mechanism 2 is also connected to the control valve 17.

  The motor generator 12 is connected to a power storage system 120 including a battery via an inverter 18A. An operation device 26 is connected to the pilot pump 15 through a pilot line 25. 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.

  FIG. 3 is a block diagram showing the configuration of the power storage system 120. The storage system 120 includes a capacitor 19 as a storage battery, a step-up / down converter, and a DC bus 110. In the present embodiment, a capacitor having a large capacity such as an electric double layer capacitor is used as the capacitor 9.

  The DC bus 110 as a constant voltage power storage unit controls transmission and reception of power between the capacitor 19 and the motor generator 1. 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 operation state of the motor generator 12. The DC bus 110 is disposed between the inverter 18 </ b> A and the step-up / down converter 100, and transfers power between the capacitor 19 and the motor generator 12. Further, the inverter 20 is provided with an inverter voltage detector 114 for detecting the voltage value of the inverter 20 and an inverter current detector 115 for detecting the current value of the inverter 20. The inverter voltage value and the inverter current value detected by the inverter voltage detection unit 114 and the inverter current detection unit 115 are supplied to the controller 30. Further, the inverter voltage detection unit 114 and the inverter current detection unit 115 may be installed in the DC bus 110.

  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 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 performs switching control between the step-up / step-down operation of the step-up / step-down converter 100 based on the charging state of the capacitor 19 and the operation state of the motor generator 12 (electric (assist) operation or power generation operation). 19 charge / discharge control 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.

  Next, deterioration determination of the capacitor 19 in the above hybrid excavator will be described. In this embodiment, a capacitor is used as a capacitor.

  The electric power (energy) ΔEasm generated by the motor generator 12 can be obtained by time-integrating the output (electric power) of the motor generator 12. FIG. 5 is a graph showing the generated power when the motor generator 12 is driven to generate power. The electric power (energy) generated by the motor generator 12 is supplied to the DC bus 110 of the power storage system 120 via the inverter 18A, and is supplied to the capacitor 16 via the converter 100. Therefore, as shown in FIG. 4, the power (energy) ΔEasm generated by the motor generator 12 can be obtained by time-integrating the output power Pasm of the inverter 18A in the range from time t1 to time t2. Since the output power Pasm of the inverter 18A is represented by the product of the current Iinv on the output side of the inverter 18A and the voltage Vinv, the current Iinv and the voltage Vinv on the output side of the inverter 18A are converted into the inverter voltage detection unit 114 and the inverter current detection unit. The power (energy) ΔEasm generated by the motor generator 12 can be obtained by obtaining the output power Pasm of the inverter 18A as measured by 115 and integrating the time. Since the current Iinv and the voltage Vinv on the output side of the inverter 18A are determined according to the output power from the motor generator 12, the current Iinv and the voltage Vinv become a current and a voltage according to the output power from the motor generator 12.

ΔEasm = ∫Pasm (t) · dt
= ∫ (Iinv × Vinv) (t) · dt
It is assumed that all the electric power (energy) ΔEasm thus obtained is supplied to the capacitor 19 via the DC bus 110 and the converter 100 and stored in the capacitor 19. Therefore, the charging energy (referred to as current charging energy) accumulated in the capacitor 19 between time t1 and time t2 is equal to the power (energy) ΔEasm generated by the motor generator 12.

  Note that the output power ΔEasm of the motor generator 12 can be obtained without measuring the current I and the voltage V on the output side of the inverter 18A. For example, if the torque T of the motor generator 12 is known, the output power ΔEasm of the motor generator 12 can be obtained by the following equation. Here, N is the rotational speed of the motor generator 12.

ΔEasm = ∫ [(2π · T / 60) × N] (t) · dt
The torque T of the motor generator 12 may be a measured value, but can be a torque command value (output command value) of the motor generator 12 that is given to the inverter 18A.

  Assuming that the capacitor 19 has not deteriorated and that there is no loss until it is supplied to the capacitor 19, all of the electric power (energy) ΔEasm obtained as described above is accumulated in the capacitor 19. .

  On the other hand, if the electric power (energy) actually stored in the capacitor 19 is ΔEcap, ΔEcap can be obtained from the change in the inter-terminal voltage Vcap of the capacitor 19. The terminal voltage of the capacitor 19 is measured by the capacitor voltage detector 112. FIG. 5 is a graph showing changes in the terminal voltage Vcap of the capacitor 19 when the capacitor 19 is charged. When electric power is stored in the capacitor 19, the voltage Vcap between the terminals of the capacitor 19 increases. Therefore, the power ΔEcap stored in the capacitor 19 from time t1 to time t2 is changed from the power (energy) stored in the capacitor 19 at time t2 to the power (energy) stored in the capacitor 19 at time t2. Can be obtained by subtracting.

The electric power stored in the capacitor 19 can be obtained by (C × Vcap ² ) / 2 where C is the capacitance of the capacitor and Vcap is the inter-terminal voltage. Therefore, the electric power (energy) accumulated in the capacitor 19 at time t2 is (Cini × Vcap (t2), where Cini is the initial capacitance of the capacitor 19 and Vcap (t2) is the terminal voltage at time t2. ) ² ) / 2. Similarly, the power (energy) accumulated in the capacitor 19 at time t1 is (Cini × Vcap (), where Cini is the initial capacitance of the capacitor 19 and Vcap (t1) is the terminal voltage at time t1. t1) ² ) / 2. Here, the reason why the initial capacitance Cini of the capacitor 19 is used is to obtain the capacitance assuming that the capacitor 19 is not deteriorated.

  Therefore, when the capacitor 19 is not deteriorated, electric power (referred to as virtual charge energy) ΔEcap that would be stored in the capacitor 19 from time t1 to time t2 is obtained by the following equation.

ΔEcap = [Cini × Vcap (t2) ² ] / 2 −
[Cini × Vcap (t1) ² ] / 2
= Cini × [Vcap (t2) ² −Vcap (t1) ² ] / 2
As described above, the power (current charging energy) ΔEasm generated by the motor generator 12 and supplied to the capacitor 19 from time t1 to time t2 is obtained from the current Iinv and voltage Vinv on the output side of the inverter 18A. be able to. On the other hand, when the capacitor 19 is not deteriorated, the electric power (virtual charging energy) ΔEcap stored in the capacitor from the time t1 to the time t2 can be obtained from the change ΔVcap of the voltage between the terminals of the capacitor.

  Here, if the capacitor 19 is not deteriorated, the current charging energy ΔEasm generated by the motor generator 12 and supplied to the capacitor 19 is all accumulated in the capacitor. That is, if the capacitor 19 is not deteriorated, the current charging energy ΔEasm and the virtual charging energy ΔEcap are equal.

  On the other hand, when the capacitor 19 is deteriorated, the electrostatic capacity C of the capacitor 19 is reduced by the amount of deterioration, so that the charging energy accumulated in the capacitor 19 is reduced. Therefore, when the capacitor 19 is deteriorated, the current charging energy ΔEasm is smaller than the virtual charging energy ΔEcap.

  Therefore, it is possible to determine whether or not the capacitor 19 has deteriorated by comparing the current charging energy ΔEasm and the virtual charging energy ΔEcap. That is, if the ratio ΔEasm / ΔEcap between the current charging energy ΔEasm and the virtual charging energy ΔEcap is equal to 1 (ΔEasm / ΔEcap = 1), it can be determined that the capacitor 19 has not deteriorated. On the other hand, if ΔEasm / ΔEcap is smaller than 1 (ΔEasm / ΔEcap <1), it can be determined that the capacitor 19 has deteriorated.

  Here, a threshold value X is set for the value of ΔEasm / ΔEcap, and when ΔEasm / ΔEcap is less than or equal to the threshold value X (ΔEasm / ΔEcap), it is determined that the capacitor 19 has deteriorated. Also good. That is, the threshold value X is set as a criterion for determining the degree of deterioration, and when ΔEasm / ΔEcap becomes equal to or less than the threshold value X (ΔEasm / ΔEcap <X), it is determined that the capacitor 19 has deteriorated. In this case, the operator may be notified that the capacitor 19 has deteriorated, or the operator may be notified that it is time to replace the capacitor 19.

  Here, the ratio ΔEasm / ΔEcap between the current charging energy ΔEasm and the virtual charging energy ΔEcap is the current capacitance of the capacitor 19 (current capacitance Crel) and the initial capacitance of the capacitor 19 (initial capacitance Cini). ) And the ratio. That is, as described below, the current charging energy ΔEasm depends on the current capacitance Crel, and the virtual charging energy ΔEcap depends on the initial capacitance Cini.

ΔEasm = Crel × [Vcap (t2) ² −Vcap (t1) ² ] / 2
ΔEcap = Cini × [Vcap (t2) ² −Vcap (t1) ² ] / 2
Therefore,
ΔEasm / ΔEcap = Crel / Cini
It becomes. Further, the current capacitance Crel of the capacitor 19 can be obtained from the above formula.

Crel = 2 × ΔEasm / [Vcap (t2) ² −Vcap (t1) ² ]
In the above-described embodiment, the example in which the present invention is applied to a so-called parallel type hybrid excavator that connects the engine 11 and the motor generator 12 to the main pump 14 that is a hydraulic pump to drive the main pump has been described. The present invention drives the motor generator 12 with the engine 11, stores the electric power generated by the motor generator 12 in the power storage system 120, and then drives the main pump 14 only with the stored electric power. It can also be applied to excavators.

  The present invention can also be applied to a hybrid excavator in which the turning mechanism is electrically operated and boom regeneration is performed. FIG. 6 is a block diagram showing a configuration of a drive system of a hybrid excavator that electrically drives the turning mechanism and performs boom regeneration. 6, parts that are the same as the parts shown in FIG. 2 are given the same reference numerals, and descriptions thereof will be omitted.

  In the hybrid excavator shown in FIG. 6, a turning electric motor 21 is provided to drive the turning mechanism 2. A turning electric motor 21 as an electric work element is connected to a power storage system 120 via an inverter 20. 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. 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.

  In order to perform boom regeneration, a hydraulic motor 310 is provided in the middle of the hydraulic piping 7 </ b> A to the boom cylinder 7. The hydraulic motor 310 is mechanically connected to the generator 300, and when the hydraulic motor 310 is driven, the generator 300 is driven by the rotational force. The generator 300 is electrically connected to the power storage system via the inverter 18B.

  In this boom regeneration mechanism, when the boom 4 is lowered, the hydraulic oil returns from the boom cylinder 7 to the control valve 17. The hydraulic oil 310 is driven by the return hydraulic oil to generate a rotational force (torque). This rotational force is transmitted to the generator 300, and the generator 300 is driven to generate electric power. The electric power generated by the generator 300 is supplied to the DC bus 110 of the power storage system 120 via an inverter.

  In the hybrid excavator configured as described above, when the voltage and current of the inverter 18A are measured by the inverter voltage detection unit 114 and the inverter current detection unit 115 in order to calculate the current charging energy ΔEasm, the inverter 18B and the inverter 20 Is temporarily stopped. Similarly, when the voltage and current of the capacitor 19 are measured by the capacitor voltage detector 112 and the capacitor current detector 113 in order to calculate the virtual charge energy ΔEcap, the driving of the inverter 18B and the inverter 20 is temporarily stopped. The

  The present invention can also be applied to, for example, a hybrid bulldozer shown in FIG. In the hybrid bulldozer shown in FIG. 7, the blade 52 attached to the bulldozer main body 50 is hydraulically driven by a lift cylinder 54 and a tilt cylinder 56. The left and right crawler belts 58A and 58B are driven by left and right drive wheels 60A and 60B driven by an electric motor.

  FIG. 8 is a diagram showing the configuration of the drive system of the hybrid bulldozer. In FIG. 8, the same components as those shown in FIG. 2 are denoted by the same reference numerals, and the description thereof is omitted. In FIG. 8, the mechanical power system is indicated by a double line, the high-pressure hydraulic line is indicated by a solid line, the pilot line is indicated by a broken line, and the electric drive / control system is indicated by a 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 the hydraulic system in the hybrid bulldozer. The lift cylinder 54 and the tilt cylinder 56 are connected to the control valve 17 via a high pressure hydraulic line.

  The motor generator 12 is connected to a power storage system 120 including a capacitor as a battery via an inverter 18A. A left running motor 64A is connected to the power storage system 120 via an inverter 20A. The left traveling motor 64A drives the left driving wheel 60A via the left driving transmission 62A. In addition, a right running motor 64B is connected to the power storage system 120 via an inverter 20B. The right traveling motor 64B drives the right driving wheel 60B via the right driving transmission 62B.

  The operating device 26 is 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.

  Similar to the configuration shown in FIG. 3, power storage system 120 includes a capacitor 19 as a power storage, a buck-boost converter, and a DC bus 110. A large capacity capacitor such as an electric double layer capacitor can be used as the capacitor 19.

  As described above, the power storage system 120 of the hybrid bulldozer is also provided with the capacitor 19 as a capacitor, and the deterioration of the capacitor according to the above-described embodiment can be determined.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 1A, 1B Hydraulic motor 2 Turning mechanism 2A Turning hydraulic motor 3 Upper turning body 4 Boom 5 Arm 6 Bucket 7 Boom cylinder 7A Hydraulic piping 7B Boom angle sensor 8 Arm cylinder 9 Bucket cylinder 10 Cabin 11 Engine 12 Electric power generation Machine 13 Transmission 14 Main pump 15 Pilot pump 16 High pressure hydraulic line 17 Control valve 18A, 18B, 20 Inverter 19 Capacitor 21 Electric motor for turning 25 Pilot line 26 Operating device 26A, 26B Lever 26C Pedal 26D Button switch 27 Hydraulic line 28 Hydraulic line 29 Pressure sensor 30 Controller 50 Bulldozer body 52 Blade 54 Lift cylinder 56 Tilt cylinder 58A, 58B Left and right crawlers 60A, 60B Left and right Driving wheel 62A, 62B Left / right drive transmission 64A, 64B Left / right traveling motor 100 Buck-boost converter 110 DC bus 111 DC bus voltage detector 112 Capacitor voltage detector 113 Capacitor current detector 114 Inverter voltage detector 115 Inverter current detector 120 Power storage system

Claims (5)

A hybrid work machine having a hydraulic pump driven by an engine, a motor generator connected to the engine, and a capacitor for supplying electric power to the motor generator,
When the motor generator is in a power generation operation, current charging energy is calculated as electric power output from the motor generator, and when the current charging energy is supplied to the capacitor based on the initial capacitance of the capacitor. A hybrid type work machine that calculates virtual charge energy as electric power stored in the battery and compares the current charge energy and the virtual charge energy to determine deterioration of the battery. A hybrid work machine according to claim 1,
A hybrid work machine that determines that the battery has deteriorated when the virtual charging energy is larger than the current charging energy. A hybrid work machine according to claim 1 or 2,
A hybrid work machine that calculates the current charging energy from a current and a voltage corresponding to output power from the motor generator. A hybrid working machine according to any one of claims 1 to 3,
A hybrid work machine that calculates the current charging energy from an output command value of the motor generator. A hybrid type work machine according to any one of claims 1 to 4,
A hybrid work machine that calculates the virtual charge energy from a voltage between terminals of the battery.

Images