JP2005207383A - Engine control method in hybrid system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve fuel consumption and reduce noise by utilizing the function of the starter of a motor generator having high silentness and responsiveness to bring a low fuel consumption state into an engine stop state in the auto deceleration control of an engine and reduce the effect of exhaust gases on the environment by reducing the exhaust gases in a hybrid system having the motor generator. <P>SOLUTION: In this hybrid system having the auto deceleration function to bring the engine 2 into the low fuel consumption state when a state in which a load applied to the engine 2 lowers below a pre-set specified value is continued for a pre-set delay time or longer, the low fuel consumption state of the engine in the auto deceleration function is brought into the stop state of the engine 2. When the engine 2 is recovered, the motor generator 40 is operated as a motor to start the engine 2. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a hybrid system, and more particularly to a hybrid system including a motor generator that functions as both a generator and an electric motor. In the present invention, “hybrid” means that at least mechanical driving force and electric power are extracted from the engine.

Conventionally, as a hybrid system applied to an electric vehicle or a work machine, a configuration in which a motor (motor) and a generator are separately provided, and a configuration in which a motor generator having a function of the motor and the generator is provided are provided. Things are known.
The hybrid system including the motor generator is applied to a construction machine such as a hydraulic excavator, and performs torque assist by operating the motor generator as an electric motor based on the relationship between the engine load torque and the fuel injection amount. In addition, a technique for controlling whether the power storage device (battery) is stored by operating as a generator to bring the engine close to an optimal operating state is known (for example, see Patent Document 1).

  Conventionally, in hydraulic construction machines such as those mentioned above, a delay time that has been set has elapsed since the time when the load was reduced, when no work or traveling was performed, or when all of the operating levers were all neutral. So, when the engine speed is set to a low speed (idle speed) lower than the set speed, so-called auto-decel control is carried out, so that fuel consumption is reduced and noise is reduced. (For example, refer to Patent Document 2).

JP 2003-27985 A JP-A-8-21269

In the auto-decel control performed by the conventional construction work machine, etc., the engine is operated at a low speed even in the low fuel consumption state (idling state) when the load is not working or running. The fuel consumption is suppressed as compared with the normal operation, but since the engine is in the operating state even in this state, the fuel is consumed, and exhaust gas and noise are generated. In other words, in order to further reduce fuel consumption and noise, it is desirable to stop the engine when work or running is not being performed. However, in a conventional working machine or the like, if the engine is controlled to be stopped every time a state where work or running is not performed, there is a risk that smooth work or running may be hindered. In other words, once the engine is in a fuel-efficient state, when the work or running is started again, in order to immediately return the engine speed to the original set speed, the engine is held at a certain speed. It was necessary to let me.
Also, today, environmental problems such as air pollution due to engine exhaust gas are becoming serious, and it is also a social request to stop idling without working or running.

  Therefore, in the present invention, in a hybrid system equipped with a motor generator, the low fuel consumption state in engine auto-decel control is set to the engine stop state by utilizing the starter function of the motor generator having high silence and responsiveness. It is an object of the present invention to further improve fuel efficiency and reduce noise by making it possible to reduce the influence of exhaust gas on the environment by reducing exhaust gas.

  The problems to be solved by the present invention are as described above. Next, means for solving the problems will be described.

  That is, according to the first aspect of the present invention, an engine, a motor generator, and a control unit that controls these are provided, and a state in which a load applied to the engine falls below a preset specified value is set in advance by the control unit. A hybrid system having an auto-decel function that puts the engine into a fuel-efficient state if the delay time continues for longer than the set delay time. The engine is started by operating the motor generator as a motor.

  According to a second aspect of the present invention, an engine, a motor generator, and control means for controlling them are provided, and whether the motor generator is operated as a motor or a generator according to a speed command from the control means. In the hybrid system to be controlled, when the state where the actual rotational speed of the engine exceeds the speed command continues for a predetermined delay time or more, the engine is stopped, and at least one operation is performed from the engine stopped state. When the lever is operated, the motor generator is operated as a motor so as to start the engine.

  As effects of the present invention, the following effects can be obtained.

  In claim 1, compared with the idling state, which is a low fuel consumption state in the conventional auto-decel function, the time during which the engine is operating is reduced by the amount of the idling state. Reduction can be achieved, and the influence of exhaust gas on the environment can be reduced. Further, due to the quietness of the motor generator, it is possible to reduce the noise at the start-up when the engine is returned from the stopped state. Furthermore, the high responsiveness of the motor generator enables smooth work and travel without causing a sense of incongruity due to the auto-decel function during work and travel.

  According to the second aspect of the present invention, when the load-reduced state in which work or traveling is not performed continues for a certain period of time, the time during which the engine is operating is reduced, so that fuel consumption can be improved and noise can be reduced. The influence exerted can be reduced. Further, due to the quietness of the motor generator, it is possible to reduce the noise at the start-up when the engine is returned from the stopped state. Furthermore, the high responsiveness of the motor generator enables smooth work and running without causing a sense of incongruity due to the auto-decel function during work or running.

Next, embodiments of the invention will be described.
1 is a diagram showing a configuration of a hybrid system, FIG. 2 is a diagram showing a list of operation modes of the hybrid system, FIG. 3 is an explanatory diagram showing a starter function of the hybrid system, and FIG. 4 is an explanatory diagram showing an assist function of the hybrid system. FIG. 5 is an explanatory diagram showing the charging (power generation) function of the hybrid system, FIG. 6 is a control block diagram for a VVVF inverter converter, FIG. 7 is a control block diagram for a buck-boost chopper, and FIG. 8 is a diagram showing a load pattern. FIG. 10 is a diagram showing a method for implementing a simulated load pattern, FIG. 10 is a diagram showing the relationship between the engine and motor output and the isobaric power line, FIG. 11 is a diagram showing a droop characteristic line, and FIG. FIG. 13 is an explanatory diagram showing reduction of engine rotation fluctuation due to engine load fluctuation, and FIG. 14 is a graph showing the specific gravity of battery fluid and battery circuit voltage. Shows the engagement, Figure 15 is a diagram showing the relationship of the battery liquid specific gravity and battery depth of discharge (DOD).

First, the configuration of the hybrid system will be described with reference to FIG.
In this hybrid system, the output shaft 4 of the engine 2 can be driven by both the engine 2 and the motor generator 40 that functions as an electric motor (motor). The driving force taken out from the output shaft portion 4 is transmitted to the output portion 6 via the clutch portion 4a, and various working portions such as a work machine, a traveling wheel in a moving body, etc. Drives underwater propulsion propellers, etc.

The motor generator 40 is a wheel-in motor directly connected to the engine in which the drive shaft is connected to the crankshaft of the engine 2, and is interposed between the main body side of the engine 2 and the output shaft portion 4.
The motor generator 40 functions as a generator or a motor, and is connected to a variable voltage variable frequency (hereinafter referred to as VVVF) inverter converter 42 of the inverter unit 41. The VVVF inverter converter 42 is connected to a battery 14 that is a power storage device via a step-up / step-down chopper 44. When the motor generator 40 functions as a motor, the power supplied from the battery 14 is supplied to the motor generator 40 via the inverter unit 41. On the other hand, when the motor generator 40 functions as a generator, the electric power generated by the motor generator 40 by driving the engine 2 is stored in the battery 14 via the inverter unit 41.

The inverter unit 41 includes a VVVF inverter converter 42 and a step-up / step-down chopper 44, and the VVVF inverter converter 42 and the step-up / step-down chopper 44 are connected to the system controller 7 via a sequencer 43. The system controller 7 including the sequencer 43 serves as control means. The system controller 7 controls operations to be performed on the control target, the order thereof, and the like based on the state of the control target, the engine speed, and external signals from various actuators. Therefore, various control signals are communicated between the system controller 7 and the sequencer 43, and signal exchange between the system controller 7, the VVVF inverter converter 42 and the step-up / down chopper 44 is performed via the sequencer 43. Is called. A signal such as a start signal or a speed command (motor command), which will be described later, is transmitted from the system controller 7 to the VVVF inverter converter 42. Between the system controller 7 and the step-up / down chopper 44, a start signal, charging start / A signal relating to the charging current is communicated.
In addition, a voltage sensor 45 is connected to the inverter unit 41, and the voltage sensor 45 detects a voltage of each unit such as an inverter DC voltage or a battery voltage of the inverter unit 41.

The motor generator 40 has a function as a motor (see M1 and M2 in FIG. 2, see FIGS. 3 and 4) and a function as a generator (see M3 to M5 in FIG. 2 and FIG. 5). Demonstrate each function according to the situation.
In other words, in the present hybrid system, when the motor generator 40 is operated as a motor, the VVVF inverter converter 42 is operated as an inverter, and the electric power supplied from the battery 14 is boosted by the step-up / down chopper 44 and the motor generator 40 is operated. When the motor generator 40 is operated as a generator, the VVVF inverter converter 42 is operated as a converter, and the power generated by the motor generator 40 is stepped down by the step-up / down chopper 44 and stored in the battery 14. It is characterized by.

  That is, when the motor generator 40 functions as a motor, the electric power supplied from the battery 14 is supplied to the motor generator 40, and the motor generator 40 is thereby operated. DC power fed from the battery 14 is input to the VVVF inverter converter 42 via the step-up / step-down chopper 44. At this time, the step-up / step-down chopper 44 functions as a boost chopper, boosts the power supply voltage of the battery 14 to a predetermined voltage, and outputs the boosted voltage to the VVVF inverter converter 42. At this time, the VVVF inverter converter 42 functions as an inverter, converts the input DC power into AC power having a predetermined voltage and frequency, and supplies the converted AC power to the motor generator 40.

  The VVVF inverter converter 42 controls the rotation speed and torque of the motor generator 40 that operates as a motor in accordance with a command (speed command / control signal) from the system controller 7. As described above, the drive shaft of the motor generator 40 is connected to the crankshaft of the engine 2, and when the motor generator 40 operates as a motor, the drive force of the motor generator 40 is transmitted to the engine 2, which will be described later. The starter function and the assist function by the motor generator 40 are exhibited.

  On the other hand, when the motor generator 40 functions as a generator, part or all of the driving force of the engine 2 is used for the operation of the motor generator 40, and the motor generator 40 is operated by the driving force from the engine 2. Power generation is performed. The electric power generated by the motor generator 40 by driving the engine 2 is input to the VVVF inverter converter 42 as three-phase AC power. At this time, the VVVF inverter converter 42 functions as a converter, and rectifies and smoothes AC power input from the motor generator 40 to convert it into DC power. The DC power converted by the VVVF inverter converter 42 is input to the battery 14 via the step-up / step-down chopper 44, and is thereby stored in the battery 14. At this time, the step-up / step-down chopper 44 functions as a step-down chopper and steps down the DC power output from the VVVF inverter converter 42 to a predetermined voltage and stores it in the battery 14.

  As described above, when the motor generator 40 operates as a motor, the VVVF inverter converter 42 functions as an inverter that converts DC power fed from the battery 14 into AC power. When operating as a generator, the bidirectional power conversion device functions as a converter that converts AC power generated by the motor generator 40 into DC power.

  Thus, since the voltage supplied from the battery 14 to the motor generator 40 can be boosted by using the step-up / step-down chopper 44 in the inverter unit 41, if the output (electric power) from the battery 14 is the same. The current can be reduced as the voltage increases (power = current × voltage). Thereby, in the wiring connecting the buck-boost chopper 44 and the VVVF inverter converter 42 and the wiring connecting the VVVF inverter converter 42 and the motor generator 40, the loss lost due to the resistance of the wiring of the load current that flows when a load is applied. (Copper loss) can be reduced.

  Further, by using the step-up / down chopper 44, the battery 14 can be reduced in size. That is, the higher the voltage supplied to the motor generator 40 that is driven as a motor, the more advantageous the motor function of the motor generator 40 is. In order to supply at a higher voltage, the battery 14 needs to be enlarged. By using the step-up / step-down chopper 44, it is possible to boost the voltage even if the voltage supplied from the battery 14 is low, so that the battery 14 need not be enlarged. Thereby, the space saving and weight reduction in the airframe which mounts this hybrid system can be achieved.

  On the other hand, the adjustment of the driving force (rotation speed) of the engine 2 is performed by operating an operation lever 9 such as a regulator lever provided in the operation unit 8. The operation lever 9 is provided with a position sensor (not shown) for detecting the lever position of the operation lever 9, and this position sensor is connected to the system controller 7. The operation unit 8 includes various switches such as a VVVF start (rotation speed) instruction switch, a CVCF (constant voltage constant frequency) start switch, a step-up / down chopper start switch, a storage start switch, and a storage current instruction switch as switching operation means. These various switches are connected to the system controller 7.

  When the operation lever 9 is operated, the position of the operation lever 9 is detected by the position sensor, and a signal corresponding to the lever position is input to the system controller 7. Then, the system controller 7 operates the shift actuator 21 and the throttle actuator 22 based on the input signal.

  The shift actuator 21 is connected to the clutch portion 4a, and is controlled to operate the clutch of the clutch portion 4a by the operation of the shift actuator 21. By operating the clutch in this manner, the driving force from the output shaft portion 4 to the output portion 6 is connected / disconnected. The shift actuator 21 is provided with a potentiometer (not shown) for detecting the shift position. The potentiometer is connected to the system controller 7, and the shift position detected by the potentiometer is input to the system controller 7.

The throttle actuator 22 is constituted by a rack and pinion type DC motor (throttle motor), and is connected to the throttle of the engine 2. The operation of the throttle actuator 22 changes the throttle position (throttle opening). The fuel injection amount in the engine 2 is adjusted by the change in the throttle position so that the driving force (rotation speed) of the engine 2 can be adjusted. That is, the throttle actuator 22 functions as a rotation speed adjusting means for the engine 2. The DC motor constituting the throttle actuator 22 is connected to the system controller 7, and the DC motor is controlled by a command sent from the system controller 7. Further, the throttle actuator 22 is provided with a potentiometer (not shown) for detecting the throttle position. The potentiometer is connected to the system controller 7, and the throttle position of the throttle actuator 22 detected by the potentiometer is input to the system controller 7.
In this manner, the operating force of the engine (rotational speed) is adjusted by operating the operating lever 9 and adjusting the lever position. However, when each control of the motor generator 40 described later is being performed, the fuel injection amount is not adjusted by operating the operation lever 9. That is, the motor generator 40 is controlled in a state where the fuel injection amount (instructed rotational speed) required from the lever position of the operation lever 9 is constant.

In the hybrid system configured as described above, the system controller 7 as the main controller functions as follows to control the hybrid system.
As described above, the system controller 7 is connected to the position sensor attached to the operation lever 9 in the operation unit 8, and is attached to the shift actuator 21 and the throttle actuator 22, and the shift actuator 21 and the throttle actuator 22, respectively. Connected to a potentiometer.

  The system controller 7 is connected to the engine 2, and the engine speed is input from the engine 2 to the system controller 7. The engine speed is detected by a speed sensor (not shown) attached to the engine 2. The engine speed detected by the rotation sensor is also input to the VVVF inverter converter 42.

  The system controller 7 is connected to a VVVF inverter converter 42, and the system controller 7 sends a start signal for a motor generator 40 as a motor and a predetermined speed command to the VVVF inverter converter 42. Based on these signals, VVVF inverter converter 42 controls motor generator 40 when operating as a motor. On the other hand, the VVVF inverter converter 42 sends signals such as the rotational speed, torque, and AC voltage value of the motor generator 40 that operates as a motor to the system controller 7. The rotation speed of the motor generator 40 is the rotation speed when the motor generator 40 is operated as a motor, and is detected by the rotation sensor. That is, since the motor generator 40 is configured to always rotate synchronously with the crankshaft of the engine 2, the rotational speed of the engine 2 can be known by detecting the rotational speed of the motor generator 40 with the rotational speed sensor. Therefore, the rotational speed sensor functions as an engine rotational speed detection means. The AC voltage of the motor generator 40 is an AC voltage supplied from the VVVF inverter converter 42 when the motor generator 40 is operated as a motor.

  The system controller 7 is connected to the step-up / down chopper 44, and the system controller 7 sends an activation signal, a charge start instruction, a charge current (limiter) instruction, etc. to the step-up / down chopper 44. The connected battery 14 is controlled. On the other hand, the step-up / down chopper 44 sends a signal related to the voltage of the battery 14, the charge / discharge current, and the like to the system controller 7. The system controller 7 can know the state of the battery 14 by detecting the voltage of the battery 14 detected by the voltage sensor 45 and the charge / discharge current.

  The hybrid system configured as described above has, for example, an operation mode as shown in FIG. 2, and a starter function (see FIG. 3), an assist function as functions of the motor generator 40 in the operation state of each operation mode. (See FIG. 4) and a charging (power generation) function (see FIG. 5). Hereinafter, each operation mode will be described.

  FIG. 3 shows the operation of the electric circuit and the transmission state of the driving force when the engine 2 is started (started). The engine 2 is started by supplying electric power from the battery 14 to the motor generator 40 and causing the motor generator 40 to function as a motor. When starting the engine 2, a relay (not shown) is turned on by operating the start key by the operator, and an engine start command is input to the system controller 7. The system controller 7 sends a start signal for the engine 2 to the VVVF inverter converter 42 and the step-up / down chopper 44. As a result, the power supplied from the battery 14 is boosted by the step-up / step-down chopper 44 that functions as a boost chopper, is converted into a required voltage and frequency by the VVVF inverter converter 42 that functions as an inverter, and is supplied to the motor generator 40 as AC power. Supplied. In this way, the motor generator 40 operates as a motor. Since the drive shaft of the motor generator 40 is connected to the crankshaft of the engine 2 as described above and always rotates synchronously, the engine 2 in a stopped state is started by driving the motor generator 40 as a motor.

  Thus, since the motor generator 40 that operates as a motor also has a starter function, and the motor generator 40 is used as a starter when the engine 2 is started, it is not necessary to provide a cell motor (starter motor) separately. Space can be achieved, and the mounting space of the power engine can be reduced in the airframe to which the hybrid system is applied. In addition, the manufacturing cost can be reduced. Furthermore, compared with a cell motor, noise during engine start-up and quick start-up are possible.

  After the start of the engine 2, the motor generator 40 is operated as a generator to constantly charge the battery 14, and the motor generator 40 is moved to the motor only when a “torque assist request” described later is generated. To assist in torque assist.

  FIG. 4 shows the operation of the electric circuit and the transmission state of the driving force at the time of torque assist by the motor generator 40. “Torque assist” means that the motor generator 40 is operated as a motor and the motor generator 40 covers a part of the driving load of the engine 2.

  When performing torque assist, the system controller 7 outputs a predetermined speed command to the VVVF inverter converter 42 and outputs an activation signal to the step-up / down chopper 44. As a result, the battery 14 is discharged, and the power supplied from the battery 14 is boosted by the step-up / step-down chopper 44 that functions as a boost chopper, and is converted into a required voltage and frequency by the VVVF inverter converter 42 that functions as an inverter. Then, it is supplied to the motor generator 40 as AC power. In this way, the motor generator 40 operates. When this torque assist is performed, when the engine 2 is under a heavy load or when acceleration is performed, the motor speed is reduced when the engine speed is lower than the speed command or when torque fluctuation occurs. The generator 40 is driven as a motor. At this time, the engine 2 is also driven, and the sum of the driving forces of the motor generator 40 and the engine 2 becomes the driving force of the output shaft portion 4.

  As described above, the motor generator 40 functioning as a motor performs appropriate torque assist according to the torque assist request, so that the output of the engine 2 is supplemented. Therefore, the engine 2 can be downsized. In addition, by the appropriate torque assist by the motor generator 40, it is possible to improve the acceleration performance and drivability of the work machine and the like, improve the fuel consumption, reduce the noise, and improve the exhaust color.

  FIG. 5 shows the operation of the electric circuit and the driving force when the battery 14 is charged with the electric power generated by the motor generator 40, that is, when the motor generator 40 is operated as a generator and the battery 14 is charged. The transmission state is shown. At this time, the output shaft 4 and the motor generator 40 are driven by the engine 2. In this state, the load torque applied to the engine 2 is smaller than the output torque of the engine 2, and the surplus torque of the engine 2 is used for power generation by the motor generator 40. In other words, only the engine 2 corresponds to the work load, and the motor generator 40 operates as a generator to generate power by driving the engine 2, and the battery 14 is charged by the power generation by the motor generator 40. It is in a state.

  When the battery 14 is stored by the motor generator 40 as a generator, the system controller 7 outputs a charge start instruction to the VVVF inverter converter 42 and the step-up / step-down chopper 44. The electric power generated by the motor generator 40 is rectified and smoothed by the VVVF inverter converter 42 and converted into DC power, and then stepped down by the step-up / step-down chopper 44 and stored in the battery 14. At this time, the VVVF inverter converter 42 functions as a converter.

Further, in the present hybrid system, the power storage of the battery 14 performed by operating the motor generator 40 as a generator in this way includes power storage by regenerative power generation of the motor generator 40.
For example, when this regenerative power generation occurs, when this hybrid system is applied to a hydraulic construction machine such as a hydraulic excavator, the front work machine having a boom, an arm, a bucket, etc. For example, when the turning motion of the turning body to which the machine is mounted is braked.

  As described above, the battery 14 stored by the motor generator 40 operating as a generator includes the battery stored by the regenerative power generation by the motor generator 40, so that the boom can be lowered or the swing operation of the swinging body can be braked as described above. Inertial energy can be effectively taken out as regenerative power, and the charging efficiency of the battery 14 by the motor generator 40 can be improved.

  Similarly, when the motor generator 40 is operating as a generator, there is a state in which no electric load is applied to the motor generator 40, that is, an operating state of a non-electric load. In this operation mode, the VVVF inverter converter 42 and the step-up / step-down chopper 44 are stopped, the motor generator 40 as a generator is substantially stopped, and only the engine 2 is operating alone. That is, in this operation mode, the output of the engine 2 and the load on the engine 2 are in a balanced state, and efficient operation is performed only by the engine 2. Even when the battery 14 is fully charged by the power generation by the motor generator 40, the potential difference between the inverter unit 41 and the battery 14 is reduced, so that the power supply from the battery 14 and the charging to the battery 14 are stopped. Only the engine 2 is operating alone.

The functions of the hybrid system described with reference to FIGS. 3 to 5 correspond to the operation modes shown in FIG. 2 as follows.
M1 shown in FIG. 2 is an operation mode in which the starter function is exhibited by the motor generator 40 that functions as the motor described with reference to FIG. M2 is an operation mode in which the assist function by the motor generator 40 that functions as the motor described with reference to FIG. 4 is exhibited. M3 to M5 are operation modes in which the charging (power generation) function by the motor generator 40 functioning as the generator described with reference to FIG. 5 is exhibited, and M3 is an operation state in which the motor generator 40 is a non-electric load. An operation mode in which only the engine 2 is operated alone, M4, is generated when regenerative power generation is performed by the motor generator 40 while the engine 2 is generating power while a work load is applied to the engine 2. An operation mode in which the regenerative power is stored in the battery 14, and M5 is an operation mode when an idle state is entered in the operation mode of M4. In this idle state, no work load is applied, and only the battery 14 is charged by the motor generator 40.

By applying a hybrid system that operates suitably in each mode as described above to a work machine or the like, in addition to the effects at the time of each operation described above, the load on the engine 2 is made constant during a series of operations. It is possible to improve the load factor (load leveling described later). As a result, it is possible to reduce the size of the engine mounted in anticipation of the output at the maximum load.
Further, as a characteristic of the engine in the low speed range, there is a case where the torque becomes smaller and unstable as the engine speed is lower. However, torque assist by the motor generator 40 can improve the torque in the low speed range. This makes it possible to improve engine performance such as improved fuel efficiency and exhaust color, and improves operability during light-load work that requires low-speed and accurate operation as a work implement and noise. Can be reduced.

Further, when the hybrid system having such a configuration is applied to a small working machine or the like, the configuration may be such that the step-up / step-down chopper 44 that steps up / down the voltage input / output to / from the battery 14 is not used. That is, when the output of the motor generator 40 that operates as a motor is relatively small and does not affect the operation, such as a small working machine, a high voltage is required to exert the motor function of the motor generator 40. Therefore, the effect of the present hybrid system can be obtained without using the step-up / down chopper 44.
In this case, the battery 14 is directly connected to the VVVF inverter converter 42, and the battery capacity of the battery 14 corresponds to the motor output of the motor generator 40 that operates as a motor.

  In this way, by adopting a configuration in which the hybrid system does not use the step-up / down chopper 44, even with a small work machine, an efficient operation by the hybrid system is possible, and an effect of reducing running costs can be obtained. It becomes possible.

Next, a method for controlling the motor generator 40 that operates as a motor and a generator will be described with reference to FIGS. 6 and 7.
Control of the motor generator 40 in this hybrid system is performed by the VVVF inverter converter 42 based on the speed command from the system controller 7, and the motor generator 40 is controlled from the VVVF inverter converter 42 as shown in FIG. Speed control as basic control for controlling the output torque command (current command) and voltage control for automatically correcting the torque command are performed in conjunction with each other. In the control of the motor generator 40, the control for the charging / discharging current to the battery 14 by the step-up / step-down chopper 44 is performed in conjunction. That is, as shown in FIG. 7, the step-up / down chopper 44 controls the charging current command based on the voltage command, and the charging current control that automatically corrects the charging current command includes the speed control and the voltage control. It is done in conjunction.

In the speed control, determination and control are performed when the motor generator 40 is operated as a motor and when the motor generator 40 is operated as a generator, and is determined based on the load of the engine 2 as a reference when performing this determination and control. This is done by comparing the actual rotational speed of the engine 2 with the engine rotational speed as the speed command.
That is, this speed control is calculated based on the actual rotational speed of the engine 2 detected by the rotation sensor that detects the rotational speed of the engine 2 by the VVVF inverter converter 42 and the load of the engine 2. Is compared with the engine speed as a speed command input to the VVVF inverter converter 42. If the actual speed of the engine 2 is smaller than the speed command (below the threshold value and lower than the set speed), VVVF The torque command from the inverter converter 42 to the motor generator 40 is increased, and the motor generator 40 is operated as a motor. On the contrary, when the actual rotational speed of the engine 2 is larger than the speed command, the torque command for the motor generator 40 is decreased from the VVVF inverter converter 42 and the motor generator 40 is controlled to operate as a generator. It is a feature. The above-described “torque assist request” is a signal sent from the VVVF inverter converter 42 to the motor generator 40 when the VVVF inverter converter 42 determines that torque assist by the motor generator 40 is necessary. This corresponds to a signal for increasing the torque command in the control. The case where the actual rotational speed of the engine 2 is smaller than the speed command corresponds to the case where the “torque assist request” is generated.

  In other words, in this speed control, when speed command> actual rotational speed, a torque assist request is generated, the torque command to the motor generator 40 is increased, a positive torque is applied to the motor generator 40, and the motor The generator 40 is operated as a motor. On the other hand, when the speed command is less than the actual rotational speed, the torque command to the motor generator 40 is decreased, and a negative torque is applied to the motor generator 40. Control to operate as.

  As shown in FIG. 1, the speed command is input from the system controller 7 to the VVVF inverter converter 42 via the sequencer 43. Based on this speed command, VVVF inverter converter 42 outputs a torque command to motor generator 40 by a control method described later. The speed command determination method will be described later in detail.

Hereinafter, speed control will be described with reference to a control block diagram shown in FIG.
In the speed control, first, a speed command (referred to as a speed command value Nv) and the actual rotational speed Nr of the engine 2 are compared by the calculation unit 30, and a deviation Nv−Nr is obtained as a comparison result. The deviation Nv−Nr is input to the PI control unit 31. The PI control unit 31 includes a PI controller 31a that performs a PI (proportional integral) control calculation based on the deviation Nv−Nr, and a limiter 31b that limits an output signal from the PI controller 31a within a certain range. ing. The PI control unit 31 calculates and outputs the deviation Nv−Nr obtained by the calculation unit 30 by the PI controller 31a, and the output passes through the limiter 31b to limit the upper and lower limit values. Generated as Npi.

  On the other hand, the actual rotational speed Nr of the engine 2 is to be compared with the speed command value Nv in the arithmetic unit 30 and is limited by the torque map 32 stored in the ROM or the like of the VVVF inverter converter 42. The torque map 32 is a map representing the relationship between the engine speed and the output torque, which is created based on the results measured in advance, taking into account the horsepower of the engine, etc., as engine torque characteristics corresponding to the throttle opening. The actual rotational speed Nr is limited by the torque map 32 within a limit value range corresponding to the rotational speed of the engine 2 and is output as the rotational speed Ntm.

Then, the PI control value Npi and the rotation speed Ntm are compared by the comparison unit 36, and the smaller value is selected, and the torque limiter 33 causes the input value to fall within the preset output torque range. If it belongs, the input value is adopted, and if not, the upper limit value (when exceeding) or the lower limit value (when falling) is adopted instead of the input value. When the smaller value selected in the comparison between the PI control value Npi and the rotational speed Ntm is a negative (−) value, that is, when the actual rotational speed of the engine 2 is larger than the speed command, Therefore, the motor generator 40 always operates as a generator because of the correspondence between the speed command and the actual rotational speed and the operation of the motor generator 40.
Thus, the output value Ns output through the torque limiter 33 becomes a torque command output to the motor generator 40. When the output value Ns is a positive (+) value, the motor generator 40 is a motor. When the motor generator 40 operates and has a negative (−) value, the motor generator 40 operates as a generator. The output value Ns becomes a final torque command output to the motor generator 40 after being corrected by voltage control described later.

  As described above, by comparing the actual rotational speed of the engine 2 and the speed command to the motor generator 40, it is controlled whether the motor generator 40 is operated as a motor or a generator. It is not necessary to perform separate control for each of the devices, and by controlling only the speed command input from the system controller 7 to the VVVF inverter converter 42, switching control of the operation of the motor generator 40 can be easily performed. It becomes possible. Further, since this control follows the speed command calculated according to the load applied to the engine 2, it is possible to perform appropriate torque assist and power generation by the motor generator 40, and the engine load can be leveled. The fuel consumption can be improved.

  In such speed control, in order to keep the DC voltage between the VVVF inverter converter 42 and the step-up / down chopper 44 within a certain range, the torque command output by the speed control is automatically corrected. That is, this control method is characterized in that voltage control is performed using the inverter DC voltage of the VVVF inverter converter 42 to correct the torque command.

Next, this voltage control will be described with reference to the control block diagram shown in FIG.
In the voltage control, first, a set value Xa (for example, a setting value) that is set corresponding to the set voltage Va determined in consideration of the withstand voltage of each part of the inverter unit 41 and stored in the ROM or the like of the VVVF inverter converter 42. A setting value Xa = 3200 with respect to the voltage Va = 320V, and a value Xdc (for example, an inverter DC voltage) corresponding to the inverter DC voltage Vdc between the VVVF inverter converter 42 and the step-up / down chopper 44 actually detected by the voltage sensor 45 The value obtained by multiplying Vdc by 10) is compared by the calculation unit 34, and a deviation Xa-Xdc is obtained as a comparison result. The deviation Xa−Xdc is input to the PI control unit 35. The PI control unit 35 includes a PI controller 35a that performs a PI (proportional integration) control calculation based on the deviation Xa-Xdc, and a limiter 35b that limits an output signal from the PI controller 35a within a certain range. ing. The PI control unit 35 calculates and outputs the deviation Xa−Xdc obtained by the calculation unit 34 by the PI controller 35a, and the output passes through the limiter 35b to limit the upper and lower limit values, so that the PI control value Xpi Is generated as

  On the other hand, as a comparison target of the PI control value Xpi generated in this way, a voltage setting value Xm corresponding to the voltage Vm based on the withstand voltage of each part of the inverter unit 41 (for example, the voltage setting for the voltage Vm = 600V). Value Xm = 6000) is preset. Then, the voltage setting value Xm and the PI control value Xpi are compared by the comparison unit 37, the smaller one is selected, and the sign is inverted and output as the correction value Xc. That is, the voltage setting value Xm is set so as to substantially serve as a limiter that limits the upper limit value of the PI control value Xpi output from the PI control unit 35.

  In this voltage control for correcting the torque command output by the speed control, if the inverter DC voltage Vdc of the VVVF inverter converter 42 is higher than the set voltage Va, the torque command to the motor generator 40 is increased, and the motor generator 40 On the contrary, if the inverter DC voltage Vdc is lower than the set voltage Va, the torque command to the motor generator 40 is decreased and the motor generator 40 is urged to generate power.

  In this way, the correction value Xc generated in the voltage control and the output value Ns generated in the speed control are compared by the comparison unit 38, and the larger value is selected. Torque command output to the motor generator 40. In order to generate a necessary torque for motor generator 40, vector control is performed in VVVF inverter converter 42 to control the magnitude, frequency, phase, etc. of the output current. Thus, the operation of the motor generator 40 is controlled by the torque command that is output while being corrected by the voltage control.

The manner of correcting the torque command by this voltage control will be described according to the operating state of the motor generator 40.
First, the case where the motor generator 40 is operating as a generator will be described.
In this case, by the speed control described above, the speed command and the actual rotational speed of the engine 2 satisfy the condition of speed command <actual rotational speed. At the time of power generation after this condition is satisfied, a current for charging the battery 14 flows from the VVVF inverter converter 42 to the battery 14 side, and the inverter DC voltage Vdc of the VVVF inverter converter 42 becomes higher than the set voltage Va. That is, the inverter DC voltage Vdc> the set voltage Va. Under this condition, the torque command to the motor generator 40 is increased by the correction by the voltage control. If this is made to correspond to the block diagram shown in FIG. 6, when the motor generator 40 is operating as a generator, the output value Ns by the speed control is a negative (−) value, and the correction value Xc by the voltage control is The value is positive (+). That is, as the torque command output, the correction value Xc is selected and the torque command is increased, so that positive torque is applied to the motor generator 40. As a result, the power generation output by the motor generator 40 is suppressed, and the inverter DC voltage Vdc also decreases.

As described above, the decreasing inverter DC voltage Vdc is settled to the set voltage Va. That is, it tries to keep the relationship of Vdc = Va. That is, when the inverter DC voltage Vdc is higher than the set voltage Va, it is decreased as described above. When the inverter DC voltage Vdc is lower than the set voltage Va, the correction value Xc by voltage control becomes a negative (−) value, The torque command is reduced, and power generation by the motor generator 40 is promoted. Even if the correction value Xc by voltage control is reduced by this power generation, the output value Ns by speed control is selected as the torque command output, and power generation is continued. When the inverter DC voltage Vdc becomes higher than the set voltage Va due to power generation by the motor generator 40, the power generation output by the motor generator 40 is suppressed by voltage control.
By performing voltage control in this way, automatic correction of the torque command is performed so that the inverter DC voltage Vdc converges to the set voltage Va.

Next, the case where the motor generator 40 is operating as a motor will be described.
In this case, according to the speed control described above, the speed command and the actual rotational speed of the engine 2 satisfy the condition of speed command> actual rotational speed. At the time of torque assist after this condition is satisfied, the current supplied from the battery 14 flows from the battery 14 to the VVVF inverter converter 42 side, and the inverter DC voltage Vdc of the VVVF inverter converter 42 becomes lower than the set voltage Va. . That is, the inverter DC voltage Vdc <the set voltage Va. Under this condition, the torque command to the motor generator 40 is reduced by the correction by the voltage control. If this is made to correspond to the block diagram shown in FIG. 6, when the motor generator 40 is operating as a motor, the output value Ns by the speed control is a positive (+) value, and the correction value Xc by the voltage control is Since power generation by the motor generator 40 is not performed, the value is always negative (−). That is, as the torque command output, the output value Ns is selected and the torque command is reduced, so that negative torque is applied to the motor generator 40. As a result, the motor output from the motor generator 40 is suppressed, and the inverter DC voltage Vdc also decreases. Then, the inverter DC voltage Vdc settles on the set voltage Vb in the step-up / step-down chopper 44 by the DC voltage control described later.

  Thus, by performing voltage control using the inverter DC voltage Vdc of the VVVF inverter converter 42 and automatically correcting the torque command output by speed control, the motor generator 40 is operated as a motor or as a generator. Since it is possible to control switching of whether to operate, and to automatically increase / decrease the torque command to the motor generator 40, appropriate control is performed according to the operation status of the motor generator 40 as a motor or a generator. Can be done. Further, it is possible to prevent the inverter DC voltage of the VVVF inverter converter 42 from exceeding the allowable range.

  In conjunction with the speed control and voltage control described above, control of the charging / discharging current to the battery 14 by the step-up / down chopper 44 is performed. That is, the DC voltage control in which the step-up / step-down chopper 44 controls the charging current command based on the voltage command and the charging current control in which the charging current command is automatically corrected are performed in conjunction with the speed control and the voltage control.

In the DC voltage control, the step-up / step-down chopper 44 controls the charging current to the battery 14 by the charge current command. As a reference for performing this control, the voltage command value by the voltage command to the step-up / step-down chopper 44 is used. Is performed by comparing the set voltage Vb and the inverter DC voltage Vdc. Here, the set voltage Vb is set slightly lower than the set voltage Va in the voltage control described above.
That is, in this DC voltage control, when the inverter DC voltage Vdc is lower than the set voltage Vb, which is a voltage command value for the buck-boost chopper 44, the buck-boost chopper 44 decreases the charging current command value, and the battery 14 When the inverter DC voltage Vdc is higher than the set voltage Vb, which is a voltage command value for the step-up / down chopper 44, the step-up / step-down chopper 44 is charged. The current command value is increased, and the charge amount to the battery 14 is increased.

  In other words, in this DC voltage control, the battery 14 is charged when the inverter DC voltage Vdc> the set voltage Vb, and the battery 14 is discharged when the inverter DC voltage Vdc <the set voltage Vb.

Hereinafter, DC voltage control will be described with reference to a control block diagram shown in FIG.
In the DC voltage control, first, a preset value Yb (for example, with respect to the set voltage Vb = 300, which is set in advance based on a set voltage Vb based on a voltage command to the step-up / step-down chopper 44 and stored in the ROM or the like of the step-up / step-down chopper 44 is used. The setting value 1500) and a value Xdc corresponding to the inverter DC voltage Vdc (the same value as in the above-described voltage control) are compared by the calculation unit 51, and a deviation Yb−Xdc is obtained as a comparison result. Prior to this comparison, in order to balance the set value Yb and the value Xdc corresponding to the inverter DC voltage Vdc, the set value Yb and the value Xdc are set in the multipliers 50 and 52 by a preset constant C1 and C2 is multiplied respectively.

  Then, the deviation Yb−Xdc is input to the PI control unit 53. The PI control unit 53 includes a PI controller 53a that performs PI (proportional integration) control calculation based on the deviation Yb−Xdc, and a limiter 53b that limits an output signal from the PI controller 53a within a certain range. ing. The PI controller 53 calculates the deviation Yb-Xdc obtained by the calculator 51 by the PI controller 53a and outputs it. The output passes through the limiter 53b and the upper and lower limit values are limited, and the PI control value It is generated as Ypi (hereinafter, charging current command value Ypi). The charging current command value Ypi is a negative (−) value because the inverter DC voltage Vdc is higher than the set voltage Vb when the battery 14 is charged.

  The charging current command value Ypi output in this way is added with a correction value, which will be described later, in the calculation unit 54, and the value input by the charging current limiter 55 falls within the preset charging current value range. If it belongs, the input value is adopted, and if not, the upper limit value (when exceeding) or the lower limit value (when falling) is adopted instead of the input value. Then, the sign is inverted and output as an output value Ys. This output value Ys becomes the command value of the charging current command in the step-up / step-down chopper 44. When the output value Ys is a positive (+) value, the inverter DC voltage Vdc is higher than the set voltage Vb, The chopper 44 increases the charge current command value to increase the amount of charge of the battery 14, and when it is a negative (−) value, the inverter DC voltage Vdc is lower than the set voltage Vb. Controls to decrease (discharge) the charge amount to the battery 14 by decreasing the charge current command value.

  Here, in the case where the motor generator 40 is operating as a motor in the above-described correction by the voltage control for the speed control, “the inverter DC voltage Vdc is the set voltage Vb in the step-up / down chopper 44 by the DC voltage control described later. In other words, when the motor generator 40 is operating as a motor, the battery 14 is discharged and the inverter DC voltage Vdc is lower than the set voltage Vb. Yes. Therefore, the step-up / step-down chopper 44 decreases the charging current command value and discharges it from the battery 14, whereby the inverter DC voltage Vdc rises to the set voltage Vb. At this time, since the motor generator 40 is not generating power, the battery 14 is not charged, and the inverter DC voltage Vdc does not become higher than the set voltage Vb. In this way, the inverter DC voltage Vdc settles to the set voltage Vb.

  Thus, by comparing the set voltage Vb based on the voltage command for the step-up / step-down chopper 44 and the inverter DC voltage Vdc, it is controlled whether the amount of charge to the battery 14 is increased or decreased, so that the inverter DC voltage Vdc is Accordingly, the charge amount of the battery 14 can be controlled, and the battery 14 can be appropriately charged / discharged when the motor generator 40 operates as a generator. Further, since the control of the charge amount of the battery 14 is performed in conjunction with the operation control of the motor generator 40, an easy control by controlling only the speed command described above becomes possible.

  In such DC voltage control, in order to keep the amount of charge to the battery 14 within a certain range and prevent the battery 14 from being overcharged / overdischarged, the charging current command output by the DC voltage control is automatically corrected. Is called. That is, the present control method is characterized in that the charging current control is performed using the actual battery voltage of the battery 14 and the charging current command is corrected.

Next, the charging current control will be described with reference to the control block diagram shown in FIG.
In the charging current control, first, the battery voltage Vbat of the battery 14 and the set voltage Vc of the battery voltage set in advance in consideration of the capacity of the battery 14 and the like are compared by the calculation unit 57, and a deviation is obtained as a comparison result. Vbat-Vc is obtained. Prior to this comparison, in order to balance the battery voltage Vbat and the set voltage Vc, the multiplier 56 multiplies the battery voltage Vbat by a preset constant C3.

  Then, the deviation Vbat−Vc is input to the P control unit 58. The P control unit 58 includes a P controller 58a that performs P (proportional) control calculation based on the deviation Vbat−Vc, and a limiter 58b that limits an output signal from the P controller 58a within a certain range. Yes. By this P controller 58, the deviation Vbat−Vc obtained by the calculator 57 is calculated and output by the P controller 58a, and this output passes through the limiter 58b to limit the upper and lower limit values. Is generated as This P control value Vp (hereinafter, correction value Vp) is a correction value for the above-described charging current command value Ypi.

  In this charging current control that corrects the charging current command output by the DC voltage control, if the battery voltage Vbat is lower than the set voltage Vc, the current in the charging direction is increased and the discharge current is suppressed to prevent overdischarge. . Further, if the battery voltage Vbat is higher than the set voltage Vc, the current in the discharging direction is increased, the charging current is suppressed, and overcharging is prevented.

  The correction value Vp output in this way is added to the charging current command value Ypi, which is an output by DC voltage control, in the calculation unit 54, and the addition value Ypi + Vp as the calculation result passes through the charging current limiter 55. The lower limit value is limited, and the sign is reversed, and this value becomes the final output of the charging current command by the step-up / step-down chopper 44.

The manner of correcting the charging current command by such charging current control will be described in accordance with the operating state of the motor generator 40.
First, the case where the motor generator 40 is operating as a generator will be described with reference to the block diagram shown in FIG.
In this case, since the battery 14 is being charged, the inverter DC voltage Vdc> the set voltage Vb, and the charging current command value Ypi, which is an output by DC voltage control, is a negative (−) value. In this case, when the battery voltage Vbat becomes higher than the set voltage Vc, the correction value Vp output from the charging current control becomes a positive (+) value. Since the correction value Vp, which is a positive (+) value, is added to the charging current command value Ypi, which is a negative (−) value, by the calculation unit 54, the final output value Ys becomes smaller and the charging current becomes smaller. The command value decreases, the charging current is suppressed, and overcharging of the battery 14 is prevented.
In this case, even if the inverter DC voltage Vdc is increased, if the inverter DC voltage Vdc is higher than the set voltage Va by the voltage control described above, the torque command to the motor generator 40 is increased and the motor generator 40 is increased. Therefore, it is possible to prevent the inverter DC voltage Vdc from becoming too high.

Next, the case where the motor generator 40 is operating as a motor will be described.
In this case, since power supply from the battery 14 is performed, the inverter DC voltage Vdc <the set voltage Vb, and the charging current command value Ypi that is output by the DC voltage control becomes a positive (+) value. In this case, when the battery voltage Vbat becomes lower than the set voltage Vc, the correction value Vp output from the charging current control becomes a negative (−) value. Since the correction value Vp, which is a negative (−) value, is added to the charging current command value Ypi, which is a positive (+) value, by the calculation unit 54, the final output value Ys becomes large and the charging current is increased. The command value increases, the power supply current is suppressed, and overdischarge of the battery 14 is prevented.

  In this way, the charging current control is performed using the battery voltage Vbat, and the charging current command output by the direct current control is automatically corrected to control whether the charging amount to the battery 14 is increased or decreased. At the same time, overcharge / overdischarge of the battery 14 can be automatically prevented.

  Each control performed by the inverter unit 41, that is, speed control and voltage control performed by the VVVF inverter converter 42, and DC voltage control and charging current control performed by the step-up / step-down chopper 44 in conjunction with these are performed by the motor. In addition to controlling the operation of the generator 40, the voltage of each part of the inverter 41 and the charging state of the battery 14 are controlled. Only the speed command input from the controller 7 is used.

Next, a method for determining the speed command will be described.
The speed command is calculated and determined by the system controller 7, transmitted from the system controller 7 to the VVVF inverter converter 42 via the sequencer 43, and detected by the rotation sensor in the VVVF inverter converter 42. This is a comparison target of the actual rotational speed of the engine 2. That is, as described above, the VVVF inverter converter 42 compares the speed command with the actual rotational speed of the engine 2 and controls whether the motor generator 40 is operated as a motor or a generator based on the comparison result.

  The speed command is an engine at an average output with respect to the load of the engine 2 at a certain time in a state where the fuel injection amount required from the lever position of the operation lever 9 is constant, that is, in a state where the indicated rotational speed by the operation lever 9 is constant. It is a command corresponding to the rotation speed. Hereinafter, a specific example of the method for determining the speed command will be described with reference to FIG.

  In this hybrid system, the speed command is executed by the system controller 7 to determine the work load applied to the engine 2 during one work cycle time (unit time U (for example, 15 seconds)) with the rotation speed indicated by the operation lever 9 being constant. The simulated load pattern Ps is calculated based on the actual load pattern Pr, and the average output A (kW) of the engine 2 with respect to the work load within the unit time U is calculated from the simulated load pattern Ps. Then, the engine speed Na at the time of this average output A output is obtained and determined based on this engine speed Na.

As shown in FIG. 8, the actual load pattern Pr means that the engine 2 is used when a certain work (for example, excavation and loading in the case of a construction machine) is performed with the rotation speed indicated by the operation lever 9 being constant. The actual measured value of the work load is patterned as one cycle per unit time U.
In the state in which the instruction rotation speed by the operation lever 9 is constant, the engine rotation speed is changed by the load applied to the engine 2. That is, when the work load applied to the engine 2 is high, the output of the engine 2 increases and the engine speed decreases. Conversely, when the work load is low, the output of the engine 2 decreases and the engine speed decreases. Get higher.

  The simulated load pattern Ps is calculated based on the actual load pattern Pr, and approximates the actual load pattern Pr by a predetermined approximation method. Hereinafter, an example of a method for calculating the simulated load pattern Ps will be described.

  First, based on the actual load pattern Pr described above, an output value H at a high load as an approximate value of an output value when a work load higher than a certain value is applied to the engine 2, a work load lower than the certain value is applied. Output value L at low load as an approximate value of the output value at the time of stoppage, and output value S at the stop time as an approximate value of the output value at the time of work stoppage are determined. Here, the rotation speed of the engine 2 at the stop-time output value S is substantially the same as the rotation speed indicated by the operation lever 9. Then, the output value at each time in the actual load pattern Pr corresponds to either the high load output value H or the low load output value L when the work load is applied (working time), and the work load is applied. In a state where the operation is not performed (when the work is stopped), the simulated load pattern Ps is obtained by approximating the actual load pattern Pr in correspondence with the output value S when stopped. That is, the actual load pattern Pr is approximated so that the output values (the high load output value H, the low load output value L, and the stop output value S) in each state are continuous, and the actual load pattern Pr A series of corresponding output values is set as a simulated load pattern Ps.

  Next, the average output A of the engine 2 with respect to the work load is calculated from the simulated load pattern Ps calculated as described above. The average output A is obtained by integrating the outputs in the simulated load pattern Ps and taking the time average. In other words, in the simulated load pattern Ps, the unit time U is the total time T1 that is the high load output value H, the total time T2 that is the low load output value L, and the total time that is the stop output value S. T3 is divided into three times corresponding to each output value (U = T1 + T2 + T3), and the average value in unit time U of the sum of the products of the respective output values and time becomes the average output A. Then, the engine speed Na at the time when the average output A is output in a state where the instruction speed by the operation lever 9 is constant is set as the speed command value. That is, the speed command is a command based on the engine speed at the average output in the simulated load pattern Ps, and the speed command value is compared with the actual engine speed Nr of the engine 2 in the speed control performed by the VVVF inverter converter 42 described above. It becomes a target (see FIG. 6).

In this way, the speed command is determined, and the lever position of the operation lever 9 that adjusts the driving force of the engine 2 is determined to be a position where the engine speed Na is obtained when the output to the work load of the engine 2 is the average output A. . The operation of the motor generator 40 corresponding to the relationship between the average output A and the simulated load pattern Ps will be described with reference to FIG.
In the simulated load pattern Ps, when the output of the engine 2 is a high load output value H, that is, the work load on the engine 2 is higher than the work load at the time of the average output A output of the engine 2, and the rotational speed of the engine 2 is When it becomes low, the output exceeding the average output A is compensated by operating the motor generator 40 as a motor to perform torque assist. Conversely, when the output of the engine 2 is the low load output value L and the stop output value S, that is, the work load on the engine 2 is lower than the work load at the time of the average output A output of the engine 2, When the rotational speed increases, the motor generator 40 is operated as a generator to generate power (charge) based on the surplus output from the actual output value to the average output A.

  The operation of the motor generator 40 will be described in correspondence with the engine speed. Based on the engine speed Na determined as the speed command (hereinafter, speed command value Na), the work load is high and the actual speed of the engine 2 is increased. When the number is lower than the speed command value Na, it is compensated by operating the motor generator 40 as a motor and performing torque assist. Conversely, when the workload is low and the actual rotational speed of the engine 2 is higher than the speed command value Na, the motor generator 40 is operated as a generator to generate power (charge). As described above, the operation of the motor generator 40 is controlled in accordance with the rotational speed of the engine 2 with the speed command value Na determined as the speed command as a reference.

  In the graph shown in FIG. 9, with the average output A as a reference, the output of the engine 2 is higher than the average output A, that is, the high load output value H side is a positive (+) value, and the average output A When the output of the engine 2 is lower than that, that is, when the low load output value L side is a negative (−) value, the integrated value of the output value in the unit time U becomes zero. In other words, by setting the output of the engine 2 to a constant average output A, the output corresponding to the motor generator 40 operating as the motor is based on the electric power stored in the battery 14 when the motor generator 40 operates as the generator. As a result, the energy balance of the motor generator 40 becomes zero.

As described above, the simulated load pattern Ps is calculated from the actual load pattern Pr actually applied to the engine 2, and the speed is obtained by using the engine speed at the time of average output A output based on the simulated load pattern Ps as the speed command value Na. By determining the command, it is possible to automatically calculate a speed command that is a target value of the engine speed according to the work load actually applied to the engine 2. As a result, torque assist and power generation by the motor generator 40 are appropriate in accordance with the working state.
Further, by performing torque assist and power generation by the motor generator 40 based on the speed command value Na determined as the speed command, the engine 2 performs a leveled constant output (average output A). The load factor of the engine 2 can be improved, that is, load leveling can be achieved. By achieving load leveling of the engine 2, it is possible to reduce the size of the engine to be mounted in anticipation of the conventionally required output at the maximum load (high load output value H).

  The speed command described above is determined based on the actual load pattern Pr in a certain unit time U. Every time this unit time U elapses, the average output A of the engine 2 for each unit time U is calculated, It is also possible to control so that the average output A for each unit time U is further averaged. That is, in the load sharing control method in this case, the average output A of the engine 2 within the unit time U is measured repeatedly and sequentially, and the moving average is taken each time, and the final average output at the time of work is calculated. By doing so, the speed command value is converged.

  Specifically, the simulated load pattern Ps1 is calculated from the actual load pattern Pr1 in a certain unit time U1. An average output A1 is calculated from the simulated load pattern Ps1. The engine speed at the time of the average output A1 is set as the speed command value Na1 when the unit time U1 has elapsed. Next, the average output A2 is similarly calculated in the next unit time U2 after the unit time U1 has elapsed. Then, the average value of the average output A1 and the average output A2 is calculated when the unit time U2 has elapsed. The average value of the average outputs A1 and A2 is the average output when the unit time U2 has elapsed. The engine speed at the average output is set as a speed command value when the unit time U2 has elapsed. Thereafter, while the engine 2 is operating, each average output up to that time is sequentially calculated in the same manner, and the engine speed at the time of this average output is used as the speed command value at each unit time. Converge the value.

  Thus, the speed command value is converged by sequentially measuring the average output of the engine 2 per unit time and calculating the average value of each average output until that time. Can be changed over time according to the work load. As a result, the followability of the speed command to the work load can be improved, and the assist and power generation by the motor generator 40 can be made more appropriate.

Next, an engine rotation control method according to the work load applied to the engine 2 will be described.
In this engine speed control method, the speed command value calculated by the system controller 7 is compared with the actual speed of the engine 2 based on the load applied to the engine 2, and torque assist by the motor generator 40 and The power generation is controlled to try to level the load on the engine 2.
In other words, the engine rotation control method uses the system controller 7 to calculate an average output with respect to the work load when the indicated rotation speed by the operation lever 9 is constant in the hybrid system, and the actual engine 2 detected by the rotation sensor. When the engine speed is lower than the average engine speed (speed command value), the torque command to the motor generator 40 is increased from the VVVF inverter converter 42, and torque assist is performed by the motor generator 40. On the other hand, when the actual engine speed of the engine 2 is higher than the engine speed at the average output, the torque command from the VVVF inverter converter 42 to the motor generator 40 is decreased, and the electric power generated by the motor generator 40 is supplied to the battery. 14 to store electricity It is characterized by controlling.

In FIG. 10, the horizontal axis represents the rotational speeds of the engine 2 and the motor generator 40, and the left vertical axis represents the brake mean pressure (Brake Mean Pressure) converted to torque. The right vertical axis is the horsepower (output) of the engine 2.
The engine maximum torque curve TPe shows the relationship between the rotational speed of the engine 2 and the maximum torque (driving force) within a range permitted by exhaust gas regulations and the like.
The equal horsepower line is composed of a series of points at which the horsepower (output) obtained from the product of the engine speed and torque on the graph of engine speed and torque is equal for each horsepower E1, E2,. It is a curve and shows the characteristics of the engine. This horsepower (output) is obtained from a pump load (work load) such as a variable displacement hydraulic pump that is driven by an engine and supplies pressure oil to various actuators provided in a work machine or the like. That is, it shows the torque required to produce a constant horsepower (output) when the engine is driven at a certain rotational speed.

  As shown in FIG. 11B, the droop characteristic lines D1 and D2 are determined in consideration of the engine speed when the engine 2 is loaded at a certain idling speed, fuel consumption, and the like. Is a plot of the relationship between the rack position of the rack gear of the rack and pinion type DC motor that constitutes. As shown in this figure, the control in which the fuel injection amount increases when the engine 2 is loaded, but the engine speed decreases, is called droop control. The droop characteristic line indicating the characteristics of the droop control is the operation lever. By operating 9 in the direction in which the fuel injection amount increases, the engine speed is increased (D1 → D2).

  When the load applied to the engine 2 changes, the engine 2 automatically changes the rotational speed of the engine 2 so that the fuel injection pump automatically injects the fuel so that the engine 2 reaches the indicated rotational speed by operating the operation lever 9. The engine 2 is provided with a mechanical governor (not shown) as a speed governing device for adjusting the amount and keeping the engine speed constant. This mechanical governor includes a governor weight that rotates in conjunction with the rotation of the engine 2, a governor spring, and a governor lever. The injection amount is adjusted. In this mechanical governor, when the engine 2 speed increases, the centrifugal force acting on the governor weight increases, the governor spring is compressed and the governor lever is actuated to reduce the injection amount, and conversely the engine 2 speed. As the engine speed decreases, the centrifugal force acting on the governor weight decreases, and the governor lever is actuated in the direction to increase the injection amount by the elastic force of the governor spring. With such a configuration, the rotational speed of the engine 2 is kept constant. Be drunk. For this reason, the droop characteristic line of the engine 2 provided with the mechanical governor becomes a substantially straight line as shown in FIG.

In FIG. 11B, the horizontal axis represents the engine speed, and the vertical axis represents the rack position of the control rack. Ra is a no-load rack position, which is a rack position in a state where no load is applied to the engine 2, that is, a state in which the engine 2 is at the original fuel injection amount and the rotational speed required by the operation lever 9. Rb is a limit rack position, which is a rack position when the engine 2 is in a high load state, that is, a state where the rotational speed of the engine 2 is low and the fuel injection amount is the largest. That is, when the load applied to the engine 2 is large while the instruction rotation speed by the operation lever 9 is constant, the state of the engine 2 moves to an upper state on the droop characteristic line, and conversely, when the load decreases, the droop characteristic It will move to the state below on the line.
When a point having the same output as the output of the engine 2 at an arbitrary point Dp1 on the droop characteristic line D1 is taken on the droop characteristic line D2, the position of the point Dp2 is obtained. That is, when the operation lever 9 is operated in the fuel injection amount increasing direction while the output of the engine 2 is constant, the rack position is also moved in the injection amount increasing direction.

  FIG. 11A is a diagram showing the rack position indicated by the vertical axis in FIG. 11B converted to the axial torque of the engine 2. From this figure, it can be seen that the shaft torque decreases due to the movement from the point Dp1 to the point Dp2. That is, if the operation lever 9 is operated in the direction of increasing the fuel injection amount while the output of the engine 2 is constant, the engine speed increases and the shaft torque decreases.

The engine rotation control will be described with reference to FIG. 10 showing the relationship between the droop characteristic lines D1 and D2 and the equal horsepower lines.
In this control, first, the system controller 7 calculates the average output of the engine 2 with respect to the work load in a state where the indicated rotational speed by the operation lever 9 is constant. The average output here is calculated in the same manner as the above-described average output A, and will be described using the same reference numerals. The equal horsepower line at the average output A of the engine 2 is the equal horsepower line of the horsepower Ea in FIG. Further, the operation lever 9 is set to a position where the output of the engine 2 becomes the average output A, and the droop characteristic line at this position of the operation lever 9 is set to D1. That is, the engine speed at the point Ce that is the intersection of the equihorse power line of the horsepower Ea and the droop characteristic line D1 becomes the speed command value Na as the speed command described above. The purpose of this control is to maintain the operating state of the engine 2 at the average output A and the rotational speed at the speed command value Na by the torque assist and power generation by the motor generator 40, thereby reducing the load on the engine 2. It is to achieve leveling.

  In FIG. 10, the state of the engine 2 at the point Ce, which is the intersection of the equihorse force line of the horsepower Ea and the droop characteristic line D1, is a state in which the actual rotational speed of the engine 2 and the speed command value Na coincide. In this state, neither torque assist nor power generation by the motor generator 40 is performed. That is, with reference to the state of the engine 2 at this point Ce, when the work load increases from this state and the engine speed decreases, torque assist is performed by the motor generator 40, and the work load decreases and the engine speed increases. The motor generator 40 is controlled to store the battery 14.

  Specifically, when a high load is applied from the state where the engine 2 is at the point Ce, the engine speed decreases, and the state of the engine 2 moves upward along the droop characteristic line D1. In this case, if the horsepower with respect to the load applied to the engine 2 is E3, the engine 2 moves to a point Ce1 which is an intersection of the droop characteristic line D1 and the equal horsepower line of the horsepower E3. Thus, the torque exceeds the engine maximum torque Te at the engine speed N1. That is, the state at the point Ce1 becomes an overload state exceeding the engine maximum torque Te that can be exhibited by the engine 2 at the engine speed N1. In order to avoid such a state, torque assist is performed by the motor generator 40, and the torque is improved while maintaining the rotational speed of the engine 2 at the speed command value Na to compensate for the insufficient output. In this case, since the engine 2 is injected with fuel to rotate at the speed command value Na, even if a load is applied and the engine speed decreases, the motor generator 40 compensates for the shortage of torque. The speed command value Na can be maintained.

  If a load corresponding to the horsepower E3 is applied at the point Ce by performing torque assist by the motor generator 40, the engine 2 avoids the state of the point Ce1 and moves to the state of the point Cem. At this point Cem, torque is applied by the motor generator 40 while the engine 2 is kept at the speed command value Na from the state of the point Ce, and the output E3 is performed with the total torque of the engine 2 and the motor generator 40. Indicates the state. In other words, in the engine 2 alone, when a load corresponding to the horsepower E3 is applied from the state of the point Ce, the engine 2 moves to the state of the point Ce1, but by performing torque assist by the motor generator 40, the engine speed is obtained. Is increased by (Na-N1), and (E3-Ea) is supplemented as horsepower. Furthermore, the engine 2 apparently operates at the position of the point Ce, but the droop characteristic line D1 is maintained with the engine speed maintained at the speed command value Na by torque assist by the motor generator 40. From this, it is possible to obtain an output on the droop characteristic line D2, which is a state in which the indicated rotational speed by the operation lever 9 is increased. In short, the torque transmitted from the VVVF inverter converter 42 to the motor generator 40 when a work load is applied and the actual rotational speed of the engine 2 falls below the speed command value Na when the rotational speed indicated by the operating lever 9 is constant. The command is increased and torque assist by the motor generator 40 is performed.

  When the load is reduced from the state where the engine 2 is at the point Ce, the engine speed is increased, and the state of the engine 2 moves downward along the droop characteristic line D1. In this case, for example, if the horsepower with respect to the load of the engine 2 is E1, the engine 2 moves to a point Ce2 that is the intersection of the droop characteristic line D1 and the equihorsepower line of the horsepower E1, and therefore the engine speed is It will go up to N2. However, since the engine 2 is controlled so as to keep the output at the average output A and the rotation speed at the speed command value Na, the motor generator 40 generates electric power by this surplus output and charges the battery 14. In short, when the indicated rotational speed by the operating lever 9 is constant, the work load is reduced and the actual rotational speed of the engine 2 is higher than the speed command value Na, the data is transmitted from the VVVF inverter converter 42 to the motor generator 40. The torque command is decreased, and the electric power generated by the motor generator 40 is stored in the battery 14.

  In this way, load leveling of the engine 2 can be achieved by performing engine rotation control based on the engine speed at the time of average output with respect to the work load. As a result, it is possible to improve fuel efficiency and to exhibit a torque that is equal to or greater than the engine maximum torque of the engine 2 and to reduce the size of the engine 2 that is mounted in anticipation of the output at the maximum load.

  Further, in this engine rotation control, even when the average output A is increased and the speed command value Na is taken in the low speed range, when the actual engine speed of the engine 2 is lower than the speed command value Na, Since torque assist is performed by the motor generator 40, the motor generator 40 can be controlled in accordance with the height of the work load, and torque assist can be performed in accordance with the work content. Thereby, it is possible to improve the torque in the low speed region, and to improve the engine performance of the engine 2 such as improvement of fuel consumption and exhaust color.

The engine rotation control as described above will be described from the aspect of current flow.
That is, in this control, when the actual rotational speed of the engine 2 falls below the speed command value Na, electric power is supplied from the battery 14 to the motor generator 40 to drive the motor generator 40 and torque assist. On the contrary, when the actual rotational speed of the engine 2 is higher than the speed command value Na, the motor generator 40 generates power using the driving force of the engine 2 and the generated power is stored in the battery 14. Control to do.

  Specifically, when the actual rotational speed of the engine 2 detected by the rotation sensor falls below the speed command value Na, the direct current supplied from the battery 14 is supplied to the VVVF inverter via the step-up / down chopper 44. Input to the converter 42. At this time, the step-up / step-down chopper 44 functions as a boost chopper, boosts the discharge voltage of the battery 14 to a predetermined voltage, and outputs the boosted voltage to the VVVF inverter converter 42. At this time, the VVVF inverter converter 42 functions as an inverter, converts the input DC power into AC power having a predetermined voltage and frequency, and supplies the converted AC power to the motor generator 40. Then, torque assist by the motor generator 40 is performed.

  On the contrary, when the actual rotational speed of the engine 2 detected by the rotation sensor is higher than the speed command value Na, part or all of the driving force of the engine 2 is used for the operation of the motor generator 40 as a generator. The motor generator 40 generates electric power. The electric power generated by motor generator 40 is output to VVVF inverter converter 42 as three-phase AC power. At this time, the VVVF inverter converter 42 functions as a converter, and rectifies and smoothes AC power input from the motor generator 40 to convert it into DC power. The DC power converted by the VVVF inverter converter 42 is input to the battery 14 via the step-up / step-down chopper 44, and thereby stored in the battery 14. At this time, the step-up / step-down chopper 44 functions as a step-down chopper, and steps down the DC power input from the VVVF inverter converter 42 to a predetermined voltage and stores it in the battery 14.

  Thus, by performing engine rotation control, the load level of the engine 2 can be leveled, and the operation of the motor generator 40 and the charging / discharging of the battery 14 can be linked to adjust the energy balance of the motor generator 40. It becomes possible and it can aim at improvement in fuel consumption.

Next, engine rotation control in the low speed region of the engine 2 will be described.
Generally, as a characteristic of the engine in a low speed region, the lower the engine speed, the lower the output, and the smaller the torque, the more unstable. Therefore, when the engine 2 is started or when the engine speed is lowered due to a high work load, the load on the engine 2 is likely to be overloaded, and exhaust gas and smoke are likely to be generated. In addition, for example, in a working machine such as a tractor, when working while moving the machine at a low speed, in a ship or the like during trolling while performing low-speed navigation, and in a hydraulic construction machine such as a hydraulic excavator, There are also scenes where the engine requires high torque in a low speed range, such as when the boom of a front working machine having a bucket or the like is raised. In view of such a point, in this control, torque is improved in the low speed region of the engine 2 by engine rotation control in which torque assist is performed by the motor generator 40 in the low speed region of the engine 2. Hereinafter, engine rotation control in the low speed region of the engine 2 will be described with reference to FIG.

  FIG. 12 shows a motor maximum torque curve TPm showing the relationship between the rotation speed of the motor generator 40 as a motor and the maximum torque (driving force) in addition to the engine maximum torque curve Tpe shown in FIG. . The engine maximum torque curve Tpe corresponds to a torque map in this control. As can be seen from this figure, assuming that the engine speed is lower than the engine speed R2, the engine maximum torque in the low speed area of the engine 2 decreases as the engine speed decreases. . On the other hand, the motor maximum torque of the motor generator 40 as a motor is stable in a low speed range, and has a characteristic that when the rotational speed becomes higher than a certain rotational speed, the torque decreases as the rotational speed increases. In this control, the engine performance in the low speed range of the engine 2 is improved by utilizing the contradictory torque characteristics in the low speed range of the engine 2 and the motor generator 40.

That is, in this control, when the engine speed detected by the rotation sensor falls within a preset low speed range, the torque command to the motor generator 40 that operates as a motor is increased from the VVVF inverter converter 42, and the motor The generator 40 is controlled to perform torque assist.
Specifically, the rotation speed of the engine 2 as a low speed region is set in advance and stored in the VVVF inverter converter 42. In the present embodiment, the low speed region of the engine 2 is set to the engine speed R1 to R2 (for example, approximately 1000 to 2000 rpm). As described above, the rotation speed of the engine 2 is detected by the rotation sensor as the engine rotation speed detection means, and is input to the VVVF inverter converter 42. When it is determined that the engine speed input by the VVVF inverter converter 42 is in the low speed range, the torque command from the VVVF inverter converter 42 to the motor generator 40 is increased, and torque assist by the motor generator 40 is performed. To control.

  Thus, by performing torque assist by the motor generator 40 in the low speed range from the engine speed R1 to R2, the total torque of the engine 2 and the motor generator 40 operating as a motor becomes the maximum torque. In FIG. 12, the maximum torque in the low speed range is an engine + motor maximum torque curve TPem representing the sum of the engine maximum torque curve Tpe and the motor maximum torque curve TPm in the range from the engine speed R1 to R2. Become.

  Thus, by performing the engine rotation control in the low speed region of the engine 2, it is possible to prevent a decrease in output in the low speed region, and to improve the torque in the low speed region. This makes it possible to improve engine performance such as improved fuel economy and exhaust color, and to improve operability and reduce noise during work requiring low speed and high torque as a work implement. be able to. Furthermore, it is possible to obtain an effect that black smoke emission can be suppressed at the start-up of the engine 2.

Next, a description will be given of a case where the engine rotation control method in the low speed region of the engine 2 is performed based on the load torque applied to the engine 2.
In this case, the engine rotation control in the low speed region of the engine 2 is performed based on the engine maximum torque curve Tpe as a torque map, and when the load torque applied to the engine 2 exceeds the value of the engine maximum torque curve Tpe, the motor Torque assist by the generator 40 is performed. That is, when the engine speed detected by the rotation sensor is in the low speed range, the load applied to the engine 2 based on the engine maximum torque curve Tpe indicating the relationship between the engine speed and the engine maximum torque stored in advance. When the torque exceeds the engine maximum torque, a torque command for the motor generator 40 is increased from the VVVF inverter converter 42 and the motor generator 40 is controlled to perform torque assist.

  Specifically, the system controller 7 stores in advance, as a torque map, an engine maximum torque curve Tpe indicating the relationship between the engine speed and the engine maximum torque of the engine 2. It should be noted that the system controller 7 may store at least the load torque corresponding to the upper limit value corresponding to the engine speed. Here, the load torque applied to the engine 2 is obtained by converting the aforementioned horsepower (output) into torque. When the system controller 7 determines that the engine speed input by the VVVF inverter converter 42 is in the low speed range, the load torque applied to the engine 2 exceeds the engine maximum torque at the engine speed. It is determined whether or not. As a result of this determination, when it is determined that the load torque applied to the engine 2 exceeds the maximum engine torque at the engine speed, the speed command from the system controller 7 to the VVVF inverter converter 42 is increased, as described above. As the speed command increases, the torque command from the VVVF inverter converter 42 to the motor generator 40 is increased, and the motor generator 40 is controlled to perform torque assist.

  Referring to FIG. 12, when a high load is applied to the engine 2 in the low speed range where the engine speed is from R1 to R2, the point Ce indicating the state of the engine 2 moving on the droop characteristic line D1 is It moves upward along the droop characteristic line D1. When the load on the engine 2 becomes a certain level or more and the point Ce moves upward from the engine maximum torque curve Tpe (see Ce3 in the figure), torque assist by the motor generator 40 is performed.

  As described above, when the load torque applied to the engine 2 exceeds the engine maximum torque in the low speed region of the engine 2, the motor generator 40 performs torque assist so that the engine maximum torque of the engine 2 is actually increased during work. Since torque assist by the motor generator 40 can be performed only when the above load torque is applied, torque assist corresponding to the work load applied to the engine 2 is possible. As a result, it is possible to compensate for a decrease in the output of the engine 2 in the low speed range, so that an overload state of the engine 2 can be prevented, and the torque in the low speed range of the engine 2 can be improved. The engine performance can be improved.

Furthermore, when the engine rotation control in the low speed region of the engine 2 is performed based on the load torque applied to the engine 2, it can be controlled as follows.
In this case, when the load torque applied to the engine 2 approaches a certain value of the engine maximum torque curve TPe, torque assist by the motor generator 40 is performed. That is, when the engine speed detected by the rotation sensor falls within the low speed range, the engine maximum torque is calculated based on the engine maximum torque curve Tpe indicating the relationship between the engine speed stored in advance and the engine maximum torque. When the difference from the load torque applied to the engine 2 becomes smaller than a preset value, the torque command to the motor generator 40 is increased from the VVVF inverter converter 42 and the motor generator 40 performs torque assist. To do.

  Specifically, when it is determined that the engine speed input by the VVVF inverter converter 42 is in the low speed range, the difference between the engine maximum torque at the engine speed and the load torque applied to the engine 2 is the system It is determined whether or not the torque difference d is preset and stored in the controller 7. As a result of this determination, when it is determined that the difference between the engine maximum torque at the engine speed and the load torque applied to the engine 2 is smaller than the torque difference d, a speed command is sent from the system controller 7 to the VVVF inverter converter 42. By increasing the speed command as described above, the torque command from the VVVF inverter converter 42 to the motor generator 40 is increased, and the motor generator 40 performs torque assist.

  Referring to FIG. 12, a curve obtained by translating the engine maximum torque curve TPe in the engine control method based on the load torque applied to the engine 2 described above downward by a torque difference d is a simulated engine maximum torque curve in this case. TPe ′ is controlled so that the motor generator 40 performs torque assist before the load torque applied to the engine 2 reaches the original maximum engine torque. That is, when a high load is applied to the engine 2 in a low speed range where the engine speed is from R1 to R2, the point Ce indicating the state of the engine 2 moving on the droop characteristic line D1 is along the droop characteristic line D1. Move up. When the load applied to the engine 2 exceeds a certain level and the point Ce moves upward from the simulated engine maximum torque curve TPe ′ (see Ce4 in the figure), torque assist by the motor generator 40 is performed.

  The engine maximum torque curve Tpe as the torque map described above may be stored in advance in the VVVF inverter converter 42. In this case, the comparison between the load torque applied to the engine 2 and the engine maximum torque is performed in the VVVF inverter converter 42. From this comparison result, it is determined whether or not the torque command for the motor generator 40 from the VVVF inverter converter 42 is increased.

  As described above, when the load torque applied to the engine 2 approaches the engine maximum torque above a certain level, the load torque applied to the engine 2 has a margin with respect to the engine maximum torque by performing torque assist by the motor generator 40. Since the torque assist is performed by the motor generator 40 from the state, the torque in the low speed region of the engine 2 can be improved and the smoke in the vicinity of the engine maximum torque of the engine 2 can be reduced. Thereby, improvement of engine performance, such as improvement of fuel consumption and improvement of exhaust color, can be aimed at.

  By the way, in this hybrid system, when the engine 2 is subjected to a load of a relatively short time with respect to the above-described work load, the number of revolutions of the engine 2 generated at the moment when the load is applied and when the load is released. The engine generator 40 can reduce the engine rotation fluctuation and level the load of the engine 2 by performing torque assist and power generation by the motor generator 40 even for the fluctuation of the engine (engine rotation fluctuation). In this case, it is desirable to use an electric double layer capacitor instead of the battery 14 as the power storage device. Hereinafter, reduction of engine rotation fluctuation and use of an electric double layer capacitor as a power storage device will be described with reference to FIG.

  The upper part of FIG. 13A shows a case where a load W having a magnitude w1 is applied to the engine 2 for a certain period of time from a state where no load is applied to the engine 2. In this case, the engine speed fluctuates as shown in the figure below. In other words, from the rotational speed n0 of the engine 2 in an unloaded state, at the moment when the load W is applied, the engine rotational speed decreases more rapidly than the rotational speed n1 of the engine 2 corresponding to the magnitude w1 of the load W. Thereafter, the rotational speed n1 is settled. Then, at the moment when the load W is released, the engine speed increases more rapidly than the rotational speed n0 in a state where no load is applied. As described above, when the engine 2 is loaded, minute pulsation of the engine (engine rotation fluctuation) occurs in a short time due to load fluctuation due to the inertial force of the load at the moment when the load is applied and when the load is released.

  When this engine rotation fluctuation occurs, a rapid decrease in the engine speed at the moment when the engine 2 is loaded is suppressed by performing torque assist by the motor generator 40 as described above. Further, when the engine speed rapidly increases (regeneration) at the moment when the load applied to the engine 2 is released, the motor generator 40 generates power. That is, the engine rotation fluctuation is suppressed by performing torque assist and power generation by the motor generator 40 even when the engine 2 fluctuates due to a minute load other than the work load.

  Specifically, the engine speed corresponding to the load applied to the engine 2 is set as the target engine speed, and the fluctuation value from the target engine speed of the actual engine speed detected by the rotation sensor is equal to or greater than a predetermined value. Then, torque assist or power generation by the motor generator 40 is performed, and the engine rotation fluctuation rate due to the load fluctuation of the engine 2 is kept within a certain range. That is, at the moment when the engine 2 is loaded, when the engine speed decreases and the deviation (fluctuation) from the target speed exceeds a certain value, the motor generator 40 is operated as a motor to perform torque assist. Conversely, if the engine speed increases and the deviation (fluctuation) from the target speed exceeds a certain value at the moment when the load applied to the engine 2 is released, the motor generator 40 is changed to a generator. To generate electric power, and the battery 14 is charged with the generated electric power. The target rotation speed corresponds to the instruction rotation speed depending on the lever position of the operation lever 9, and is preset in the system controller 7 or the VVVF inverter converter 42. Then, the fluctuation of the engine speed from the target speed is detected by the system controller 7 or the VVVF inverter converter 42. The engine speed fluctuation rate is the ratio of the fluctuation value of the actual speed of the engine 2 from the target speed to the target speed.

  For example, when this is made to correspond to FIG. 13A described above, the rotation speed n1 corresponding to the load w1 applied to the engine 2 becomes the target rotation speed corresponding to the load W, and no load is applied. The rotational speed n0 in the state becomes the target rotational speed in the no-load state of the engine 2. Then, at the moment when the load W is applied to the engine 2, the engine speed decreases, and the fluctuation value from the target speed n1 corresponding to the load W of the engine speed, that is, the difference between the target speed n1 and the engine speed is obtained. When the predetermined value δn is exceeded, the motor generator 40 is operated as a motor to perform instantaneous torque assist, and the load fluctuation of the engine 2 in this case is reduced. Conversely, the engine speed increases at the moment when the load W applied to the engine 2 is released, and the fluctuation value of the engine speed from the target speed n0 corresponding to the no-load state of the engine 2, that is, the target speed n0. When the difference between the engine speed and the engine speed becomes larger than the specified value δn, the motor generator 40 is operated as a generator to perform instantaneous power generation, and the load fluctuation of the engine 2 in this case is reduced. The prescribed value δn may be set to a different value depending on engine characteristics or the like depending on whether the engine speed fluctuates from the target speed to the lower side or increases.

  Thus, the pulsation of the engine 2 can be suppressed by performing torque assist and power generation by the motor generator 40 even with respect to engine rotation fluctuation due to minute load fluctuation in a short time of the engine 2. As a result, the engine efficiency can be improved, the fuel consumption can be improved, and the exhaust gas can be reduced.

The upper part of FIG. 13B shows the amount of fluctuation that affects the engine speed due to torque assist and power generation by the motor generator 40 that is performed when the engine speed fluctuates. That is, when torque assist is performed by operating the motor generator 40 as a motor, the assist amount for the engine 2 is shown. When power generation is performed by operating the motor generator 40 as a generator, the engine used for this power generation is displayed. The consumption of the number of rotations of 2 will be shown.
Thus, by operating the motor generator 40 and performing load leveling in a short time, the engine speed changes as shown in the following figure. That is, the engine rotation fluctuation at the time of load fluctuation is suppressed by torque assist and power generation by the motor generator 40, and the fluctuation value of the engine rotation speed from the target rotation speed is suppressed to be smaller than the specified value δn.
As described above, in order to perform instantaneous torque assist and power generation by the motor generator 40 in a short time, it is necessary that power supply and charging by the power storage device be performed so that the functions are exhibited in a short time. That is, the power storage device is also required to be responsive to torque assist and power generation by the motor generator 40 in a short time and charge / discharge efficiency. Therefore, an electric double layer capacitor is used that has better charge / discharge efficiency than a battery and can handle instantaneous charge / discharge.

  In a battery, electricity is stored by using a chemical change, but in this electric double layer capacitor, electricity is stored as an electron by an electrostatic action without a chemical change. Therefore, charging / discharging efficiency is high and it is possible to cope with instantaneous charging / discharging. That is, when a battery is used as the power storage device, power supply when performing torque assist by the motor generator 40 is relatively responsive, but a time delay occurs when the power generated by the motor generator 40 is stored. In other words, when trying to cope with engine rotation fluctuations due to load fluctuations in a short time, if a battery is used as a power storage device, charging time is more than discharging time when trying to store the same amount of electricity as the supplied electricity. It becomes longer and the balance of power consumption as a battery will not match. However, such a problem can be solved by using an electric double layer capacitor as the power storage device. That is, it is possible to reduce the imbalance in the charge / discharge balance of the power storage device due to suppression of engine rotation fluctuation due to load fluctuations in a short time with respect to the engine 2, and to charge the power storage device satisfactorily. Insufficiency can be prevented.

Furthermore, the following effects can be obtained by using an electric double layer capacitor as a power storage device in the hybrid system.
The electric double layer capacitor is resistant to repeated charging and discharging, and can extend the life of the power storage device. In addition, the electric double layer capacitor has low pollution because the raw material is made of an electrolyte and carbon that are nearly harmless. In addition, since the electric double layer capacitor has a wide range of endurance temperature characteristics, it is possible to obtain an effect that stable operation is possible in the operating temperature range as compared with a battery whose performance deteriorates at low temperatures. it can.

The electric double layer capacitor can also be used in combination with a battery. In this case, an electric double layer capacitor and a battery are connected in parallel as a power storage device.
As described above, by using the electric double layer capacitor and the battery together as the power storage device in the hybrid system, the battery compensates for the storage capacity of the electric double layer capacitor having the characteristic that the energy density that can be relatively stored is lower than that of the battery. be able to. As a result, it is possible to cope with the engine rotation fluctuation due to the load fluctuation in the short time described above, and to secure a sufficient storage capacity.

  In addition, the technology that suppresses the pulsation of such an engine is premixed compression that is cleaner than a gasoline engine and has fuel efficiency similar to that of a diesel engine, but has a large pulsation and is unstable compared to a gasoline engine or a diesel engine. By applying it in a hybrid system equipped with a self-ignition (HCCI) engine, it can be expected that the effect will be exhibited more.

Subsequently, an auto-decel function as an engine control method in the hybrid system will be described.
The auto-decel function is a low fuel consumption state (idling state) when the load reduction state in which no work or running is continued for a certain period of time or longer on the work machine, etc. At the start of work or traveling, the engine speed is immediately returned to the original set speed. In such an auto-decel function, the present hybrid system is characterized in that the engine 2 is brought into a stopped state instead of changing the engine 2 to the above-described decelerating speed. This will be specifically described below.

  In this hybrid system, as described above, the VVVF inverter converter 42 compares the actual rotational speed of the engine 2 with the speed command input from the system controller 7 to the VVVF inverter converter 42, and based on the comparison result. The motor generator 40 is controlled. The low load state continues, and the state in which the actual engine speed of the engine 2 exceeds the speed command value is equal to or longer than a preset delay time by comparing the actual engine speed and the speed command value. If it continues, it will control to stop the engine 2. FIG. That is, since the starter function by the motor generator 40 described above can start the engine 2 quickly, the responsiveness when the engine 2 is started again from a stopped state is high, so the low load state of the engine 2 is constant. If it continues for more than the time, the engine 2 is stopped and there is no problem in the work and running.

  Thus, by setting the low fuel consumption state of the engine 2 in the auto-decel function to the stop state of the engine 2, the idling state is compared with the idling state which is the low fuel consumption state in the conventional auto-decel function. Since the time during which the engine is operating is reduced, fuel consumption can be improved and noise can be reduced, and the influence of exhaust gas on the environment can be reduced. Further, due to the quietness of the motor generator 40, it is possible to reduce noise at the time of startup when the engine 2 is returned from the stopped state.

Next, the case where the engine 2 is started again from the stop state of the engine 2 in the auto-decel function will be described.
In the auto-decel function in the present hybrid system, the engine 2 once stopped is operated by operating the motor generator 40 as a motor when at least one operation lever 9 is operated.

The at least one operation lever 9 is at least one of a lever, such as a regulator lever, a throttle lever, and a shift lever, which are disposed in the operation unit 8 and adjusts the driving force of the engine 2, for example. When one of these is operated, the engine 2 is started by the motor generator 40.
That is, when the operation lever 9 is operated from the stopped state of the engine 2 by the auto-decel function, a signal corresponding to the lever position is input to the system controller 7. The system controller 7 that has received the signal related to the lever operation sends a start signal for the engine 2 to the VVVF inverter converter 42 and the step-up / down chopper 44. As a result, the power supplied from the discharged battery 14 is boosted by the step-up / step-down chopper 44, converted into a required voltage and frequency by the VVVF inverter converter 42, and supplied to the motor generator 40 as AC power. In this way, the motor generator 40 operates as a starter, and the stopped engine 2 is started again.

  As described above, since the motor generator 40 is caused to function as a starter from the stopped state of the engine 2 by the auto-decel function, noise at the time of the engine 2 start-up and quick start-up can be achieved. The fuel economy can be improved and noise and exhaust gas can be reduced by changing the low fuel consumption state of 2 to the stop state of the engine 2, and the high responsiveness of the motor generator 40 makes it uncomfortable due to the auto-decel function during work and running. Smooth work and running are possible without any occurrence.

In the hybrid system, the engine 2 and the motor generator 40 can be controlled based on the state of charge of the battery 14. Hereinafter, a method for controlling the engine 2 and the motor generator 40 based on the state of charge of the battery 14 will be described.
In this control method, when the charge amount of the battery 14 falls below a specified value, the motor generator 40 does not perform torque assist, and the system controller 7 adjusts the rotation speed of the engine 2 that is normally adjusted by operating the operation lever 9. By automatically controlling, the engine output (engine speed) is to be controlled to be constant. That is, in the present control method, when the state of charge of the battery 14 falls below a preset specified value, torque assist by the motor generator 40 is not performed, and the DC motor constituting the throttle actuator 22 is controlled to control the engine. The engine speed is controlled so as to keep the engine output constant by adjusting the rotational speed of 2.

First, a method for calculating the state of charge of the battery 14 (hereinafter, SOC (State of Charge)) will be described.
As described above, the AC power generated by the motor generator 40 by driving the engine 2 is rectified and smoothed by the VVVF inverter converter 42 and converted to DC power, and then converted to DC power by the step-up / down chopper 44. It is transformed and stored in the battery 14. In addition, power is supplied to the motor generator 40 by the power supplied from the battery 14 so that the motor generator 40 can be driven.

The SOC of the battery 14 is calculated by the system controller 7 from the relationship between the electromotive force of the battery 14 and the specific gravity of the battery liquid (electrolyte) of the battery 14.
If it demonstrates concretely, the battery voltage (terminal voltage of the battery 14) Vbat during charging / discharging will be represented by following Formula (1).
Vbat = E _O ± I _CD · R _O (1)
The SOC of the battery 14 is calculated using this equation. In Equation (1), E _O is the electromotive force (battery open circuit voltage) of the battery 14, I _CD is the charge / discharge current of the battery 14, and R _O is the internal resistance of the battery 14. The charging / discharging current I _CD of the battery 14 becomes a charging current or a discharging current depending on the direction of the current. In the formula (1), the charging current is positive (+) and is negative (−). Discharge current.

The battery voltage Vbat and the charge / discharge current I _CD detected by the voltage sensor 45 are transmitted from the step-up / down chopper 44 to the system controller 7 via the sequencer 43. The system controller 7 calculates the internal resistance R _O of the battery 14 based on the input battery voltage Vbat and charge / discharge current I _CD . Based on the calculated internal resistance R _O , the battery open circuit voltage E _O is calculated from Equation (1). The system controller 7 previously stores the relationship between the battery open circuit voltage E _O and the specific gravity of the battery fluid (electrolyte) of the battery 14 as shown in FIG. 14, and the specific gravity of the battery fluid as shown in FIG. The relationship with the depth of discharge of the battery 14 (hereinafter referred to as DOD (Depth of Discharge)) is stored. The system controller 7 may store the relationship between the battery fluid and the SOC in advance instead of the relationship between the battery fluid and the DOD. Both DOD and SOC are quantities representing the state of charge of the battery, and there is a relationship of DOD + SOC = 100% between the two.

When the battery open circuit voltage E _O is known, the system controller 7 calculates the specific gravity of the battery with respect to a certain battery temperature (ambient temperature) based on the relationship between the battery open circuit voltage E _O and the specific gravity of the battery fluid. Then, the DOD of the battery 14 is calculated from the calculated specific gravity of the battery fluid based on the relationship between the specific gravity of the battery fluid and the DOD, and the SOC of the battery 14 with respect to this DOD is calculated. The method for calculating the SOC of the battery 14 is an example, and the method is not limited to the above calculation method as long as the SOC of the battery 14 having a certain level of accuracy can be calculated by the system controller 7 at any time.

Then, the calculated SOC of the battery 14 is compared with the specified value SOC _min stored in advance in the system controller 7 by the system controller 7, and whether or not the SOC of the battery 14 is below the specified value SOC _min. Is judged. Here, if it is determined that the SOC of the battery 14 is lower than the specified value SOC _min , torque assist by the motor generator 40 when the above-described engine 2 is subjected to a work load higher than a certain level is not performed, instead. In addition, control is performed so as to perform load leveling of the engine 2 with respect to the work load by increasing the output of the engine 2 itself. That is, when the charge amount of the battery 14 decreases and the motor generator 40 does not perform sufficient torque assist, the discharge of the battery 14 is stopped by not performing the torque assist by the motor generator 40. Then, instead of torque assist by the motor generator 40, the engine output (engine speed) is kept constant by controlling the throttle actuator 22 that adjusts the fuel injection amount of the engine 2.

Specifically, the load leveling of the engine 2 by controlling the throttle actuator 22 is performed as follows.
As described above, the throttle actuator 22 is constituted by a rack and pinion type DC motor, and the rack gear of the throttle actuator 22 is connected to the governor lever of the mechanical governor described above. The DC motor is automatically controlled by the system controller 7, thereby adjusting the fuel injection amount of the engine 2 and adjusting the engine speed.

That is, in the state where the SOC of the battery 14 calculated as described above by the system controller 7 is lower than the specified value SOC _min , a high work load is applied to the engine 2, and the actual rotational speed of the engine 2 is set to the speed command. When the value is smaller than the value, a command is sent from the system controller 7 to the DC motor of the throttle actuator 22 to operate the governor lever in the direction of increasing the fuel injection amount, and the engine speed is increased so that the engine output becomes constant. Hold at the command value. When the SOC of the battery 14 is lower than the specified value SOC _min due to the power generation by the motor generator 40, the control shifts to the normal torque assist control by the motor generator 40 when the SOC exceeds the specified value SOC _min .

  In this way, when the charge amount of the battery 14 is insufficient, torque assist by the motor generator 40 is not performed, and the engine output is kept constant by controlling the throttle actuator 22 of the engine 2 so that the engine 2 The characteristics of the engine 2 with respect to the work load (work speed, etc.) even when the charge amount of the battery 14 is insufficient, such as when the torque assist by the motor generator 40 is continuously performed after being in a high load state for a long time. Without changing, it is possible to eliminate a sense of incongruity (such as a rapid decrease in engine speed) due to insufficient torque assist of the motor generator 40 due to insufficient charge of the battery 14 during work. In addition, since the battery 14 can be prevented from being overdischarged, the battery performance can be prevented from being deteriorated due to the overdischarge of the battery 14 and the life can be extended.

  Further, the automatic control of the throttle actuator 22 by the system controller 7 can be controlled so as to be performed for a predetermined time from when the power supply by the battery 14 is finished. That is, in this case, until the preset time elapses after the power supply from the battery 14 with the torque assist of the motor generator 40 is completed, the torque assist by the motor generator 40 is not performed and the throttle actuator 22 is controlled. As a result, the engine speed is adjusted to keep the engine output constant by adjusting the rotational speed of the engine 2.

  Specifically, when a high work load is applied to the engine 2 and the actual rotational speed of the engine 2 becomes lower than the speed command value, torque assist is performed by the motor generator 40. Thereafter, the work load is released and the engine 2 is released. Torque assist by the motor generator 40 is not performed until a predetermined time elapses after the actual rotational speed of the motor becomes higher than the speed command value, that is, after the power supply by the battery 14 is completed. In addition, by automatically controlling the throttle actuator 22 by the system controller 7, the engine output is kept constant and the load level of the engine 2 is leveled.

  For example, a case where the throttle actuator 22 is automatically controlled for a certain period of time after the power supply by the battery 14 is finished is referred to as a “power saving mode” in the hybrid system, and the “power saving mode” is turned on / off in the operation unit 8. A switch or the like for switching may be provided, and a configuration that can be arbitrarily selected by an operator such as a work machine to which the hybrid system is applied may be employed.

  By controlling in this way, since the battery 14 is not discharged at least for a certain period of time after the power supply by the battery 14 is completed, it is possible to prevent the battery 14 from being overdischarged in advance. Further, when such control is performed, the “power saving mode” is set, and switching can be performed, so that overdischarge of the battery 14 can be prevented in accordance with the working state and load leveling of the engine 2 can be achieved. It becomes possible.

  As examples of use of the present invention, driving of a hydraulic excavator or the like in a construction machine, driving of various working units in an agricultural working machine, driving of a propeller for underwater propulsion of a ship, traveling in another moving body (for example, an automobile, etc.) It can be widely applied to the driving of the part and the turning part.

The figure which shows the structure of a hybrid system. The figure which shows the list of the operation modes of a hybrid system. Explanatory drawing which shows the starter function of a hybrid system. Explanatory drawing which shows the assist function of a hybrid system. Explanatory drawing which shows the charge (electric power generation) function of a hybrid system. The control block diagram for VVVF inverter converters. FIG. 3 is a control block diagram for a step-up / down chopper. The figure which shows a load pattern. The figure which shows the implementation method of a simulated load pattern. The figure which shows the relationship between an engine and a motor output, and an equal horsepower line. The figure which shows a droop characteristic line. The figure which shows the relationship between an engine and a motor output, and an equal horsepower line. Explanatory drawing which shows reduction of engine rotation fluctuation | variation by engine load fluctuation | variation. The figure which shows the relationship between specific gravity of a battery liquid, and a battery circuit voltage. The figure which shows the relationship between the specific gravity of a battery liquid, and the discharge depth (DOD) of a battery.

Explanation of symbols

2 Engine 7 System Controller 9 Operation Lever 14 Battery 21 Shift Actuator 22 Throttle Actuator 40 Motor Generator 42 VVVF Inverter Converter 44 Buck-Boost Chopper

Claims (2)

An engine, a motor generator, and control means for controlling these, and when the state where the load applied to the engine falls below a preset specified value by the control means continues for a preset delay time or longer, A hybrid system having an auto-decel function of bringing the engine into a low fuel consumption state,
An engine control method in a hybrid system, wherein the engine fuel consumption state in the auto-decel function is set to an engine stop state, and when the engine is returned, the motor generator is operated as a motor to start the engine. . The hybrid system includes an engine, a motor generator, and control means for controlling them, and controls whether the motor generator operates as a motor or a generator according to a speed command from the control means. And
When the state in which the actual rotational speed of the engine exceeds the speed command continues for a preset delay time or more, the engine is stopped, and when at least one operation lever is operated from the engine stopped state, An engine control method in a hybrid system, wherein a motor generator is operated as a motor so as to start the engine.

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