JP2012233312A - Hybrid work machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To ensure security of a work in a normal work period while preventing over discharging of a storage battery.SOLUTION: In a hybrid shovel, a generator motor 10 and a hydraulic pump 11 are connected to an engine 9; a capacitor 18 is charged by a generator action of the generator motor 10; and drive of the hydraulic pump is assisted by an electric motor action of the generator motor 10 through discharge action of the capacitor. When travel operation, in which the capacitor 18 only discharges without being charged, continues for a predetermined period of time and a detection value of capacitor SOC (state of charge) is equal to or lower than a reference value preliminarily set as a value with which the storage battery reaches over discharging, the hybrid shovel is configured to perform an adjustment control to adjust a pump flow rate so as to reduce the same in accordance with a difference between the reference value and the detection value.

Description

  The present invention relates to a hybrid work machine that uses an engine and a capacitor together as a power source.

  The background art will be described using an excavator as an example.

  As shown in FIG. 5, the excavator is configured such that an upper swing body 2 is mounted on a crawler type lower traveling body 1 so as to be rotatable around a vertical axis O, and a work attachment A is mounted on the upper swing body 2. .

  The work attachment A includes a boom 3 that can be raised and lowered, an arm 4 attached to the tip of the boom 3, a bucket 5 attached to the tip of the arm 4, and a boom and an arm that are hydraulic actuators for driving them. And each cylinder 6, 7, 8 of the bucket.

  Further, as another hydraulic actuator, a traveling motor that drives the left and right crawlers of the lower traveling body 1 and a swing motor that drives the upper swing body 2 to rotate (both not shown) are provided.

  On the other hand, in a hybrid excavator, a hydraulic pump that drives a hydraulic actuator and a generator motor that performs a generator action and a motor action are connected to an engine, and the capacitor is charged by the generator action of the generator motor. The generator motor is configured to assist the drive of the hydraulic pump by the electric motor action by the discharge force.

  In other words, when the power required to drive the hydraulic actuator is small, the surplus power is stored (charged) as electrical energy in the battery, and the stored power is released (discharged) when the required power is large to assist the engine. Improve fuel efficiency.

  In this hybrid system, as a technique for preventing overdischarge of the battery, a technique for detecting SOC (State Of Charge) which is a charge state of the battery and reducing the pump flow rate when the SOC value is reduced is known (Patent Document). 1).

JP 2007-247230 A

  In the excavator, a series of operations such as excavation → turning → discharging is performed as a normal operation, and charging and discharging of the capacitor are repeated in the normal operation, so that the capacitor SOC is finally maintained in an appropriate range.

  In other words, even if the SOC temporarily decreases during normal work, the SOC is recovered by subsequent charging.

  However, according to the above known technique, if the SOC decreases, the control for reducing the pump flow rate is always performed. Therefore, the output is limited (the pump flow rate is adjusted) every time the SOC is decreased.

  As a result, since the speed (working speed) and torque (working capacity) of the hydraulic actuator frequently change during normal work, there is a problem that stable work cannot be performed.

  On the other hand, an overdischarge of the battery is likely to occur when a discharge side operation in which only a discharge is performed without being charged during traveling (especially when traveling on an uphill) continues for a certain time or more. There is a high need to add output limits.

  Therefore, the present invention provides a hybrid work machine that can ensure the stability of work during normal work while preventing overdischarge of the battery.

  As means for solving the above problems, in the present invention, a hydraulic pump that drives a hydraulic actuator and a generator motor that performs a generator action and a motor action are connected to the engine, and the capacitor is charged by the generator action of the generator motor. And a pump regulator configured to assist the drive of the hydraulic pump by causing the generator motor to perform a motor action by the discharging action of the capacitor, and to control a pump flow rate that is a flow rate discharged from the hydraulic pump; And an SOC detection means for detecting an SOC value which is a charged state of the battery, in a hybrid work machine comprising: a control means for instructing the pump regulator of a pump flow rate corresponding to a pump pressure which is a discharge pressure of the hydraulic pump; Operating means for operating the hydraulic actuator, and operating the operating means And the control means performs a discharge-side continuation operation in which a discharge-side operation in which only the discharge is performed without charging the battery is continued for a preset time, and the SOC When the value of the battery SOC detected by the detection means becomes equal to or lower than a reference value set in advance as a value that leads to overdischarge of the battery, the pump flow rate is reduced according to the difference between the reference value and the detected value. It is configured to perform adjustment control to adjust to the side.

  In this case, in the hybrid work machine that includes the lower traveling body and is driven by a traveling motor that uses the hydraulic pump as a hydraulic source, the adjustment control is performed by setting the operation for which the traveling operation continues for a set time as the discharge-side continuous operation. (Claim 2).

  According to the above configuration, the pump flow rate is adjusted to the decrease side only when the discharge side operation such as the traveling operation (Claim 2) is continuously performed for the set time and the battery SOC is equal to or lower than the reference value. In other words, since the adjustment control is not performed during normal operation in which charging and discharging are repeated, stable operation can be performed while maintaining the speed and capacity of the actuator during normal operation.

  On the other hand, when the discharge-side continuation operation is performed and the battery SOC decreases below the reference value and there is a risk of overdischarge, the discharge is suddenly controlled by the adjustment control. You can avoid a situation where the speed and ability of the machine suddenly goes down.

  In this case, since the condition is that the storage SOC is lower than the reference value and the operation is continued for a set time, it is possible to ensure the operation at full output even if the operation continues on the discharge side while the SOC exceeds the reference value. After the two conditions are met, the speed and capacity gradually decrease in accordance with the decrease in SOC, so that the operator can be informed of the decrease in SOC and can be encouraged to take overdischarge avoidance means.

  According to the present invention, it is possible to ensure the stability of work during normal work while preventing overdischarge of the battery.

1 is a system configuration diagram of a hybrid excavator according to an embodiment of the present invention. It is a flowchart for demonstrating the control content in embodiment. It is a figure which shows the relationship of the pump pressure / pump flow rate as a control result by embodiment. It is a figure which shows the discharge characteristic of an electrical storage device. It is a schematic side view of an excavator.

  An embodiment of the present invention will be described with reference to FIGS. The embodiment is applied to a hybrid excavator.

  FIG. 1 shows a block configuration of the entire control system in this hybrid excavator, where a hydraulic system is represented by a solid line and an electric system is represented by a broken line.

  A generator motor 10 that performs a generator action and a motor action and a hydraulic pump 11 are connected to the engine 9.

  Although the figure shows the case where the engine 9, the generator motor 10 and the hydraulic pump 11 are connected on the same axis, the present invention connects the generator motor 10 and the hydraulic pump 11 in parallel to the engine 9 via a power divider. In this case, the same can be done in the following.

  The hydraulic pump 11 is configured as a variable displacement pump in which the displacement is changed by a pump regulator 13 controlled by a controller 12 as a control means, and the discharge amount (pump flow rate) is changed. It is supplied to a plurality of hydraulic actuators (boom, arm, bucket cylinders 6-8, travel motor, etc. in FIG. 5) via a control valve (direction switching valve) 14.

  In the embodiment, since a representative example of the discharge side operation is a traveling operation, only the driving circuit of the traveling motor 15 is illustrated as a hydraulic actuator circuit, and this is the target of control.

  Two traveling motors 15 are provided for the left and right sides corresponding to the left and right crawlers, and the hydraulic pump 11 is also provided separately for the left and right sides. However, since the content of the control is the same, only one is shown in the figure. ing.

  The pump regulator 13 may be one that operates directly by an electrical signal from the controller 12 or may be one that operates a solenoid valve by a signal from the controller 12 and operates by a hydraulic pressure from the solenoid valve. Good.

  Reference numeral 16 denotes a remote control valve as travel operation means. The control valve 14 is operated by a pilot pressure corresponding to the operation amount of the remote control valve 16, and pressure oil is supplied to and discharged from the travel motor 15 (operation direction and speed of the hydraulic actuator). Be controlled.

  The generator motor 10 is connected to a capacitor 18 ((a secondary battery such as a capacitor, a nickel hydride secondary battery, a lithium ion secondary battery) 18 via an inverter 17.

  The inverter 17 controls the switching between the generator action and the motor action of the generator motor 10, the current or torque of the generator and the motor, and the charge / discharge of the capacitor 18.

  On the other hand, as a detecting means, a pilot pressure sensor 19 as an operation detecting means for detecting a pilot pressure (running operation) output from the remote control valve 16, and a pump for controlling the pump flow rate (horsepower control) according to the pump pressure. A pump pressure sensor 20 is provided as pump pressure detection means for detecting pressure.

  Based on the signals from both the sensors 19 and 20, the controller 12 determines whether the traveling operation has been performed or whether the traveling operation has been performed for a preset time, and the voltage and current of the battery 18. It is determined whether or not the capacitor SOC value calculated from the above becomes equal to or less than a reference value set in advance as a value that leads to overdischarge of the capacitor, and the pump flow rate based on this determination is commanded to the pump regulator 13.

  The operation of this hybrid excavator including the control contents of the controller 12 will be described with reference to the flowchart of FIG.

  After the start of control, it is determined whether or not the traveling operation has been performed for a set time in step S1 of FIG. 2, and if NO, that is, if there is no traveling operation or if there is no traveling operation, As a normal command, a pump flow rate corresponding to the pump pressure is commanded to the pump regulator 13 in step S2.

  FIG. 3 shows the relationship between the pump pressure and the pump flow rate. In the case of the normal command that is NO in step S1, the pump flow rate is obtained according to the characteristic I and this is commanded to the pump regulator 13.

  Specifically, since the pump flow rate is obtained by the product of the pump rotation speed and the pump tilt, the pump regulator 13 is commanded to tilt the pump to obtain the pump flow rate corresponding to the pump pressure.

  The characteristic I in FIG. 3 is that the pump output (pump pressure × pump flow rate) is the sum of engine power and capacitor power (more precisely, the assist force of the generator motor 10 driven by the capacitor 18). It is set so as not to exceed the total supply power.

  If YES in step S1, that is, if the traveling operation has been performed for a set time, the process proceeds to step S3, and the detected value Er of the battery SOC at that time is compared with the reference value Es.

Note that the amount of energy change ΔE during the time Ts of the battery 18 is calculated from the current I and the voltage V.
ΔE = [Σ (I × V × Ts) / 3600
Is calculated (integrated).

  The capacitor SOC is obtained by expressing the ratio of the value obtained by adding ΔE to the rated charge amount α to the rated charge amount α in%, where the current charging direction is positive.

That is,
SOC = (α + ΔE) / α × 100
It becomes.

  If NO in step S3, that is, if the SOC detection value Er exceeds the reference value Es, a normal command is issued in step S2 because there is no danger of overdischarge of the battery 18.

  On the other hand, if YES, that is, if the detected value Er falls below the reference value Es, an adjusted flow rate based on the characteristic II in FIG. 3 is obtained in step S4.

  The characteristic II is a characteristic of the flow rate obtained by subtracting the flow rate obtained by multiplying the SOC value difference (Es−Er) by the gain K from the original pump flow rate based on the characteristic I, and this adjusted flow rate is commanded to the pump regulator 13. The

  As a result, the pump flow rate is reduced, the running output is reduced, and the discharge of the battery 18 is suppressed.

  FIG. 4 shows the discharge characteristics of the secondary battery (capacitor). In a constant current output state, the voltage change ΔV and the output change according to the discharge are small, and the full discharge can be performed for a long time. Then, the voltage and output suddenly go down. This characteristic becomes more conspicuous as the output is higher and the capacity is higher.

  The set time is set based on the discharge characteristics so that the adjustment control is started at a time sufficiently before the voltage and the output are suddenly reduced.

  According to this hybrid excavator, the traveling operation, which is a discharge-side operation in which only discharging is performed without being charged as described above, is continuously performed for a set time, and the detected value Er of the battery SOC is less than or equal to the reference value Es. Only when this happens, adjustment control is performed to adjust the pump flow rate to the decreasing side.

  In other words, since adjustment control is not performed during normal work in which charging and discharging are repeated, stable work can be performed while maintaining the speed and capacity of the actuator during normal work.

  On the other hand, when the traveling operation is continuously performed for a set time and the detection value Er of the battery SOC is lowered below the reference value Es due to this, the adjustment of adjusting the pump flow rate to the decreasing side occurs. Since the discharge is suppressed by the control, it is possible to avoid a situation where the speed is suddenly reduced and the capacity is suddenly reduced due to an overdischarge state.

  In this case, since the condition is that the detection value Er of the storage battery SOC has decreased to the reference value Ea or less and the continuation operation for the set time, work at full output can be ensured while the SOC exceeds the reference value, After the two conditions are met, the speed and capacity gradually decrease in accordance with the decrease in SOC, so that the operator can be informed of the decrease in SOC and can be encouraged to take overdischarge avoidance means.

Other embodiments
(1) Since the overdischarge of the capacitor is likely to occur particularly during climbing, it is detected that the vehicle is climbing from the inclination of the vehicle body, and the above adjustment control is performed only when this climbing is performed, on the condition that the set time continues and the SOC decreases. May be performed.

  (2) The present invention is not limited to the shovel, and can also be applied to other work machines (dismantling machines and crushers) configured by attaching different attachments to the same base machine as the shovel.

  In this case, in a machine in which a discharge side operation similar to traveling is performed, a configuration in which the operation is monitored and adjustment control may be performed.

DESCRIPTION OF SYMBOLS 1 Lower traveling body 2 Upper revolving body 9 Engine 10 Generator motor 11 Hydraulic pump 12 Controller as control means which also serves as SOC detection means 13 Pump regulator 14 Control valve 15 Traveling motor 16 Remote control valve as operation means 17 Inverter 18 Accumulator 19 Operation means As a pilot pressure sensor 20 Pump pressure sensor

Claims (2)

  A hydraulic pump that drives the hydraulic actuator and a generator motor that performs a generator action and a motor action are connected to the engine, and the capacitor is charged by the generator action of the generator motor, and the generator motor is discharged by the discharge action of the capacitor Is configured to assist the drive of the hydraulic pump by performing an electric motor action, and according to the pump regulator that controls the pump flow rate that is the flow rate discharged by the hydraulic pump, and the pump pressure that is the discharge pressure of the hydraulic pump In a hybrid work machine having a control means for commanding the pump flow rate to the pump regulator, an SOC detection means for detecting an SOC value which is a charge state of the battery, an operation means for operating the hydraulic actuator, and the operation Operation detecting means for detecting the operation of the means, and the control means The discharge side operation in which the discharge side operation in which only the discharge is performed without charging the capacitor is continued for a preset time is performed, and the value of the capacitor SOC detected by the SOC detection means is the overcharge of the capacitor. It is configured to perform adjustment control to adjust the pump flow rate to the decrease side according to the difference between the reference value and the detected value when the value leading to the discharge is below a preset reference value. Hybrid work machine.   In a hybrid work machine that includes a lower traveling body, and the lower traveling body is driven by a traveling motor that uses the hydraulic pump as a hydraulic source, the control means uses the operation that the traveling operation continues for a set time as the discharge-side continued operation. The hybrid work machine according to claim 1, wherein the hybrid work machine is configured to perform adjustment control.

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