JP2020029237A - Hybrid construction machine - Google Patents

Abstract

To provide a hybrid construction machine that has enhanced control responsiveness to variations in a workload while keeping power balance.SOLUTION: A hybrid construction machine includes: an engine 2: a hydraulic pump 4 driven by the engine 2; a hydraulic actuator 42 actuated by working fluid from the hydraulic pump 4; a motor generator 3 for assisting the drive of the engine 2 during power running, and generating power during regeneration; a battery 32 for charging or discharging the power generated by the motor generator 3; and an inverter 31a for controlling the power running and the regeneration of the motor generator 3 on the basis of a deviation between a target engine load factor of the engine 2 and an actual engine load factor. The target engine load factor is set on the basis of external load torque calculated from output torque of the engine 2 and output torque of the motor generator 3.SELECTED DRAWING: Figure 4

Description

  The present invention relates to a hybrid construction machine.

  Patent Literature 1 below discloses a technique of calculating an assist torque or a generation torque of an electric / generator based on a deviation between a target rotation speed of an engine and an actual rotation speed in a hybrid construction machine.

  Patent Literature 2 below discloses, in a hybrid construction machine, an output limit determined based on a torque margin obtained by a difference between an engine maximum torque determined based on an actual engine speed and an engine actual torque, There is disclosed a technique for calculating a motor torque command value based on a difference between a target engine speed and an actual engine speed.

Japanese Patent No. 4800514 Japanese Patent No. 5594748

  In Patent Literature 1, when the hydraulic load suddenly changes, the engine torque sharply increases, so that an excessive load is applied to the engine, and the engine speed may be unintentionally reduced. In addition, since the usage ratio of the engine output and the assist output of the motor / generator cannot be controlled, excessive assist may be performed, and there is a problem in control responsiveness to a change in the workload.

  According to Patent Literature 2, it is possible to prevent the motor generator from excessively assisting in accordance with the torque or the output margin of the engine. -There is also a problem that the power balance cannot be controlled because the usage ratio of the assist output of the generator cannot be controlled and the feedback control is performed based on the difference between the maximum torque of the engine and the actual torque of the engine.

  In view of the above, an object of the present invention is to provide a hybrid construction machine that can improve control responsiveness to a change in a workload while maintaining a power balance.

The hybrid construction machine of the present invention includes an upper rotating body,
A lower traveling body that supports the upper revolving body in a freely rotatable manner;
An engine housed inside the upper rotating body,
A hydraulic pump driven by the engine;
A hydraulic actuator operated by hydraulic oil from the hydraulic pump,
A motor generator that assists driving of the engine during power running and generates power during regeneration,
A battery that charges or discharges power generated by the motor generator,
An inverter that controls powering and regeneration of the motor generator based on a deviation between a target engine load factor and an actual engine load factor of the engine,
The target engine load factor is set based on an external load torque calculated from an output torque of the engine and an output torque of the motor generator.

  In the present invention, when the external load torque is larger than a first specified value, the target engine load factor may be set from a first set value to a second set value lower than the first set value.

  In the present invention, when the external load torque is smaller than a second specified value, the target engine load factor may be set from a third set value to a fourth set value higher than the third set value.

  In the present invention, the target engine load factor may be set according to a target engine speed.

  In the present invention, the target engine load factor may be set according to a value corresponding to the charged amount of the battery.

  According to the present invention, since the power running and the regeneration of the motor generator are controlled based on the target engine load factor, the actual engine load factor, and the deviation, the use of the output of the engine and the output of the motor generator only by controlling the engine Since the ratio can be controlled, control responsiveness to changes in the workload is good. Further, according to the present invention, the power running and the regeneration of the motor generator are controlled based on the deviation between the target engine load factor set based on the external load torque and the actual engine load factor. Power generation and regeneration of the motor generator suitable for the vehicle can be efficiently performed. Therefore, control responsiveness to a change in the workload can be improved while maintaining the power balance.

It is a side view showing the backhoe concerning this embodiment. It is a top view showing the backhoe concerning this embodiment. It is a figure which shows the hydraulic circuit and electric circuit mounted in a backhoe. FIG. 4 is a functional block diagram illustrating processing functions of a hybrid controller. 5 is a two-dimensional map for calculating a target engine load factor. It is a graph which shows an example of control of an engine and a motor generator. It is a graph which shows an example of control of an engine and a motor generator. 9 is a table for setting a lower limit value of a target engine load factor.

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

  First, a schematic structure of a backhoe 1 as an example of a hybrid construction machine will be described with reference to FIG. The backhoe 1 includes a lower traveling body 11, a work implement 12, and an upper revolving superstructure 13.

  The lower traveling unit 11 is driven by receiving power from the engine 2 housed inside the upper revolving unit 13, and causes the backhoe 1 to travel. The lower traveling body 11 includes a pair of left and right crawlers 11a, 11a and a pair of left and right traveling motors 11b, 11b. The left and right traveling motors 11b, 11b, which are hydraulic motors, drive the left and right crawlers 11a, 11a, respectively, so that the backhoe 1 can move forward and backward. Further, the lower traveling body 11 is provided with a blade 11c and a blade cylinder 11d for rotating the blade 11c in a vertical direction.

  The work machine 12 is driven by receiving power from the engine 2 and performs excavation work such as earth and sand. The work machine 12 includes a boom 12a, an arm 12b, and a bucket 12c, and enables excavation work by independently driving these. The boom 12a, the arm 12b, and the bucket 12c each correspond to a working unit, and the backhoe 1 has a plurality of working units.

  One end of the boom 12a is supported by a front portion of the upper swing body 13, and is rotated by a boom cylinder 12d that is movable in a stretchable manner. The arm 12b has one end supported by the other end of the boom 12a, and is rotated by an arm cylinder 12e that is movable in a stretchable manner. One end of the bucket 12c is supported by the other end of the arm 12b, and the bucket 12c is rotated by a bucket cylinder 12f that is movable in a retractable manner.

  The upper swing body 13 is configured to be swingable with respect to the lower traveling body 11 via a swing bearing (not shown). A cabin 131, a bonnet 132, a counterweight 133, a swing motor 134, an engine 2, and the like are arranged on the upper swing body 13. The upper swing body 13 swings through a swing bearing (not shown) by the driving force of the swing motor 134. The motor generator 3 driven by the engine 2 and the hydraulic pump 4 are disposed on the upper swing body 13. The hydraulic pump 4 supplies hydraulic oil to each hydraulic motor and each cylinder.

  In the cabin 131, a driver's seat 131a is arranged. A pair of operation levers (not shown) are disposed on the left and right sides of the driver's seat 131a, and a pair of traveling levers 131b, 131b are disposed in front of the driver's seat 131a. The operator controls the engine 2, each hydraulic motor, each hydraulic cylinder, and the like by sitting on the driver's seat 131a and operating the work operation levers, travel levers 131b, 131b, etc., and performs travel, turning, work, and the like. be able to.

  A bonnet 132 and a counterweight 133 are vertically arranged at the rear end of the upper swing body 13. The counter weight 133 is provided upright at the rear end of the upper revolving unit 13 and covers the engine 2. The bonnet 132 extends upward from the upper end of the counterweight 133 to reach the lower end of the rear wall of the cabin 131, and covers the engine 2 together with the counterweight 133. The rear end of the upper swing body 13 is formed in an arc shape in a plan view, and the bonnet 132 and the counterweight 133 are formed to be curved along the rear end of the upper swing body 13. The backhoe 1 of the present embodiment is of a so-called small backward turning type.

  Next, configurations of a hydraulic circuit and an electric circuit mounted on the backhoe 1 will be described. The engine 2 is a so-called horizontal engine in which the crankshaft is arranged in the left-right direction of the upper revolving unit 13, and is arranged below the driver's seat 131a. Further, the engine 2 is arranged at the rear center of the upper revolving unit 13 in plan view.

  The engine 2 includes an engine ECU 21. The engine ECU 21 is for performing control of the engine speed and other various controls. An accelerator dial 61 is electrically connected to the engine ECU 21 and generates a control signal based on an electric signal input from the accelerator dial 61. The accelerator dial 61 is an instruction device that instructs the engine ECU 21 on the target engine speed of the engine 2. Further, the engine ECU 21 can detect an actual rotation speed of the engine 2 (referred to as an actual engine rotation speed).

  The operator sets the engine speed of the engine 2 by operating the accelerator dial 61. The engine speed set by the accelerator dial 61 (referred to as a set engine speed) is instructed to the engine ECU 21 as the target engine speed of the engine 2. The accelerator dial 61 is electrically connected to the engine 2 via the engine ECU 21. The engine ECU 21 generates a control signal based on the electric signal from the accelerator dial 61 and sends the generated control signal to the engine 2. Output. That is, engine ECU 21 is a device that controls the output of engine 2, and engine ECU 21 can control the engine speed of engine 2 based on the operation of accelerator dial 61 by the operator.

  Further, the engine ECU 21 can calculate an engine load factor which is a ratio to the maximum output of the engine 2 at an arbitrary engine speed. Normally, since the hydraulic pump 4 is driven by the engine 2, the engine load ratio varies depending on the work content. The engine load factor can be calculated by various methods. For example, the engine load factor is calculated using the relationship between the engine speed and the fuel injection amount. The engine load factor is calculated using, for example, the relationship between the engine speed and the fuel injection amount stored in advance in the storage unit of the engine ECU 21. That is, the engine ECU 21 obtains the maximum fuel injection amount and the no-load fuel injection amount at the actual engine speed from the actual engine speed and the relationship between the engine speed and the fuel injection amount. Then, the engine ECU 21 calculates the ratio of the deviation between the actual fuel injection amount and the no-load fuel injection amount to the deviation between the maximum fuel injection amount and the no-load fuel injection amount to the actual engine load factor (the actual engine load factor). (Equivalent).

  The motor generator 3 is connected to one end of a crankshaft of the engine 2. The motor generator 3 is also called a motor generator, and operates as a generator during regeneration, and operates as an electric motor when it is necessary to assist the driving torque of the engine 2. The motor generator 3 is controlled by the hybrid controller 5 via the inverter / converter 31.

  The motor generator 3 is connected to a battery 32 via an inverter / converter 31. The battery 32 stores regenerative energy generated in the motor generator 3 and supplies driving energy to the motor generator 3. The battery 32 is disposed on the right side of the cabin 131 as shown in FIG.

  The inverter / converter 31 controls the motor generator 3 and the battery 32. Inverter / converter 31 discharges electric power of battery 32 to drive motor generator 3 based on an assist command from hybrid controller 5 to assist the output of engine 2. Further, inverter / converter 31 charges battery 32 with electric power generated by motor generator 3 based on a charge command from hybrid controller 5.

  The hydraulic pump 4 is connected to the motor generator 3. A plurality of hydraulic pumps 4 may be provided. A control valve 41 is connected to the hydraulic pump 4. The control valve 41 switches the direction and flow rate of hydraulic oil supplied from the hydraulic pump 4 to each hydraulic actuator 42 (the traveling motors 11b, 11b, the boom cylinder 12d, the arm cylinder 12e, the bucket cylinder 12f, etc.).

  Hybrid controller 5 outputs a control command for controlling the output of motor generator 3 to inverter 31a. In the present embodiment, the hybrid controller 5 outputs the output torque of the motor generator 3 as a command value. The output torque of the motor generator 3 is the output torque of power running or the output torque of regeneration, and defines the output torque of regeneration as positive and the output torque of power running as negative.

  The hybrid controller 5 includes an engine output torque calculator 51 that calculates the output torque of the engine 2. The engine output torque calculation unit 51 calculates the output torque of the engine 2 based on the actual engine speed, the rated torque curve of the engine 2, and the actual engine load factor input from the engine ECU 21. The output torque of the engine 2 is the output torque [Nm] of the engine 2 = the rated torque [Nm] at the actual engine speed (the rated torque at the actual engine speed obtained from the rated torque curve) x the actual engine load factor [% ] / 100.

  The hybrid controller 5 includes an external load torque calculator 52 that calculates an external load torque. The external load torque is calculated from the output torque of the engine 2 and the output torque of the motor generator 3. The output torque of the engine 2 is input from an engine output torque calculation unit 51, and the output torque of the motor generator 3 is input from an output control unit 54 described later. The external load torque is calculated by calculating external load torque [Nm] = output torque [Nm] of engine 2-output torque [Nm] of motor generator 3. As described above, the output torque of the motor generator 3 is defined as positive on the regenerative side and negative on the powering side. Therefore, the external load torque during regeneration is smaller than the output of the engine 2 and the external torque during powering is defined. The load torque becomes larger than the output of the engine 2.

  The hybrid controller 5 includes a target engine load factor calculation unit 53 that calculates a target engine load factor. The target engine load factor is calculated from the external load torque and the target engine speed. The external load torque is input from the external load torque calculation unit 52, and the target engine speed is input from the engine ECU 21. The target engine load factor is calculated by, for example, a two-dimensional map in which the external load torque and the target engine speed are input. The two-dimensional map is stored in the hybrid controller 5.

  The hybrid controller 5 includes an output control unit 54 that generates a control command based on a deviation between a target engine load factor of the engine 2 and an actual engine load factor. More specifically, the output control unit 54 calculates a load factor deviation by subtracting the actual engine load factor from the target engine load factor, multiplies the calculated load factor deviation by a proportional gain, The output torque of the motor generator 3 is calculated by the sum of the value obtained by multiplying the integral gain by the integral gain. The target engine load factor is input from the target engine load factor calculation unit 53, and the actual engine load factor is input from the engine ECU 21. The output control unit 54 outputs the calculated output torque of the motor generator 3 to the inverter 31a as a command value.

  When the target engine load factor is larger than the actual engine load factor, that is, when there is a margin in the output of the engine 2, the hybrid controller 5 controls the inverter 31 a to charge the battery 32 with the electric power generated by the motor generator 3. A control command is transmitted to the motor generator 3 via the control unit. When the target engine load factor is larger than the actual engine load factor, the output torque calculated by the output control unit 54 is positive. Therefore, in this embodiment, the positive output torque is the regenerative output torque.

  On the other hand, when the target engine load factor is smaller than the actual engine load factor, that is, when the output of the engine 2 is insufficient, the hybrid controller 5 discharges the power of the battery 32 to drive the motor generator 3. To the motor generator 3 via the inverter 31a. When the target engine load factor is smaller than the actual engine load factor, the output torque calculated by the output control unit 54 is negative. Therefore, in this embodiment, the negative output torque is the output torque of the power running.

  Here, a method of setting the target engine load factor will be described. As described above, the target engine load factor is calculated from the two-dimensional map using the external load torque and the target engine speed as inputs. FIG. 5 shows an example of this two-dimensional map. As shown in FIG. 5, when the external load torque is large (150 Nm and 200 Nm), the target engine load factor is set low, and when the external load torque is small (0 Nm and 50 Nm), the target engine load factor is set high.

  The target engine load ratio is set in accordance with the target engine speed. When the target engine speed is low, the target engine load ratio is low, and when the target engine speed is high, the target engine load ratio is low. It is set high. Since there is an engine load factor with good fuel efficiency depending on the engine speed, an effect of improving fuel efficiency can be obtained by appropriately setting the engine load factor according to the engine speed. Work load and charge / discharge balance can be balanced even at low rotation, and continuous work is possible.

  6A and 6B are graphs illustrating an example of control of the engine 2 and the motor generator 3.

  As shown in FIG. 6A, when the external load torque is larger than the first specified value T1, the target engine load factor is set from the first set value L1 to a second set value L2 lower than the first set value L1. . By setting the target engine load factor to be low when the external load is high, the response to the external load is not controlled by the motor generator 3 having a relatively slow response speed, but by the rotational governing (the rotational speed of the engine 2) of the engine 2 having a sufficient load. (Adjustment), the control responsiveness to the workload can be improved. By setting the target engine load factor low, the motor generator 3 can assist the vehicle from a state where the actual engine load factor is not so high.

  On the other hand, as shown in FIG. 6B, when the external load torque is smaller than the second specified value T2, the target engine load factor is set from the third set value L3 to the fourth set value L4 higher than the third set value L3. Is done. By setting the target engine load factor to be high when the external load is low, the output of the engine 2 can be utilized to promote the maximum charging, and the power balance of the battery 32 can be maintained.

  Further, the target engine load factor may be set according to a value corresponding to the charged amount of the battery 32. For example, the lower limit value of the target engine load factor is set by a table as shown in FIG. When the voltage of the battery 32 is high (400 V or more), the lower limit of the target engine load factor is set to 0%, which is a state in which the lower limit of the target engine load factor is not limited. Therefore, when the voltage of the battery 32 is high, the target engine load factor calculated using the two-dimensional map shown in FIG. 5 is used.

  On the other hand, as the voltage of the battery 32 decreases from 400 V, the lower limit of the target engine load factor is increased from 0%. When the voltage of the battery 32 decreases to 350 V, the lower limit of the target engine load factor is set to 80%. Is low (350 V or less), the lower limit of the target engine load factor is limited to 80%. Therefore, when the voltage of the battery 32 is low, the target engine load factor is set to 80% even if the target engine load factor calculated from the two-dimensional map shown in FIG. 5 is lower than 80%. As a result, when the charged amount of the battery 32 decreases, the lower limit of the target engine load factor can be increased to promote charging.

[Other embodiments]
In the above-described embodiment, the voltage of the battery 32 is used as the value corresponding to the charged amount of the battery 32. However, the SOC (Status of Charge) of the battery 32 may be used.

  As described above, the embodiments of the present invention have been described with reference to the drawings. However, it should be considered that the specific configuration is not limited to these embodiments. The scope of the present invention is shown not only by the description of the embodiment but also by the claims, and further includes meanings equivalent to the claims and all modifications within the scope.

DESCRIPTION OF SYMBOLS 1 Backhoe 11 Lower traveling body 13 Upper revolving superstructure 2 Engine 3 Motor generator 4 Hydraulic pump 5 Hybrid controller 21 Engine ECU
31a inverter 32 battery

Claims (5)

An upper revolving structure,
A lower traveling body that supports the upper revolving body in a freely rotatable manner;
An engine housed inside the upper rotating body,
A hydraulic pump driven by the engine;
A hydraulic actuator operated by hydraulic oil from the hydraulic pump,
A motor generator that assists driving of the engine during power running and generates power during regeneration,
A battery that charges or discharges power generated by the motor generator,
An inverter that controls powering and regeneration of the motor generator based on a deviation between a target engine load factor and an actual engine load factor of the engine,
The hybrid construction machine, wherein the target engine load factor is set based on an external load torque calculated from an output torque of the engine and an output torque of the motor generator.   The hybrid according to claim 1, wherein when the external load torque is larger than a first specified value, the target engine load factor is set from a first set value to a second set value lower than the first set value. Construction machinery.   3. The target engine load factor is set from a third set value to a fourth set value higher than the third set value when the external load torque is smaller than a second specified value. Hybrid construction machinery.   The hybrid construction machine according to claim 1, wherein the target engine load factor is set according to a target engine speed. The hybrid construction machine according to any one of claims 1 to 4, wherein the target engine load factor is set according to a value corresponding to a charged amount of the battery.

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