JP2005155252A - Power system control unit for construction machine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress fluctuation in voltage of a battery; to reduce the size and weight of a unit; to reduce costs; and to obtain a high power. <P>SOLUTION: This power system control unit for construction machines is provided with a control means 24 for detecting the fluctuation in the voltage of the battery 25, which increases torque of a hydraulic pump 23 by making an electric motor/generator 22 operate as an electric motor for assisting torque of an engine 21, when the voltage of the battery rises, and which performs control so that electrical energy generated by the generator can be stored in the battery 25 by making the electric motor/generator 22 operate as a generator, when the voltage of the battery falls. Thus, the fluctuation in the voltage of the battery 25 can be suppressed. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power system controller for a construction machine such as a hydraulic excavator, and more particularly, to a hybrid construction machine including a generator and a torque assisting motor in addition to an engine as a power source for driving the construction machine. The present invention relates to a power system control device.

  In general, a hydraulic excavator is equipped with a diesel engine as a drive source, travels with the diesel engine, and drives a hydraulic pump to operate an arm, an excavator, and the like to perform various operations. This method has a problem in terms of exhaust gas, such as exhausting black smoke, which is heavy on the engine, and also in terms of noise and fuel efficiency.

  Therefore, for the purpose of reducing the burden on the engine and improving the fuel efficiency, a configuration using a hybrid system in which a motor is provided as a power source in addition to the engine and a hydraulic pump is driven by the motor and the engine is known. (For example, refer to Patent Document 1).

Further, as shown in the same patent document 1, in the hybrid system, a generator and an electric motor are provided as a power source in addition to the engine, and the generator is driven by surplus torque of the engine. Also known is a technique for storing generated electric energy in a battery, supplying the electric energy of the battery to an electric motor as needed, assisting the engine by rotating the electric motor, and reducing the load on the engine. .
Japanese Patent Laid-Open No. 2001-16704.

  However, in the invention described in Patent Document 1, when the engine is assisted by the electric motor, the battery power is consumed and the battery voltage is lowered. On the contrary, when electric power is generated, electric energy is stored in the battery and the battery voltage is increased. This battery voltage fluctuation is not desirable because it shortens the life of the battery and restricts the control near the upper limit / lower limit of the battery voltage. In other words, at the upper limit of the voltage, it cannot be charged any more, so even if the engine has a margin, it becomes a light load operation and the fuel efficiency becomes worse. On the other hand, there is a problem that the assist cannot be performed at the lower limit of the voltage.

  Furthermore, since the invention described in Patent Document 1 has a structure in which an electric motor and a generator are prepared separately, there is a problem in that the apparatus becomes larger and heavier and the cost becomes higher.

  Therefore, there are technical problems to be solved in order to suppress the voltage fluctuation of the battery, reduce the size and weight of the device, reduce the cost, and always increase the output required for this kind of construction machine. The present invention aims to solve this problem.

  The present invention has been proposed to achieve the above object, and the invention according to claim 1 is driven by an engine, a hydraulic pump connected to the power line of the engine, and surplus torque of the engine. A construction machine comprising: a generator; a battery for storing electrical energy generated by the generator; and a torque assisting motor that converts electrical energy received from the battery into mechanical energy and supplies the mechanical energy to the hydraulic pump. In the power system control device, the battery voltage fluctuation is detected, and when the battery voltage increases, the torque assist motor is operated to increase the set torque of the hydraulic pump, and the battery voltage decreases. Control means for controlling the electric energy generated by operating the generator to be stored in the battery, Providing construction machine for power system control apparatus that suppress variation in voltage.

  According to this configuration, when the battery voltage rises, if the engine is assisted by the torque assisting motor, the torque of the hydraulic pump is increased and the battery power is consumed, the battery voltage is lowered. When the electric power is lowered, electric energy is stored in the battery when the electric power is generated by the generator, and the battery voltage rises, so that fluctuations in the battery voltage can be suppressed.

  According to a second aspect of the present invention, the hydraulic pump has an electromagnetic proportional valve for adjusting a set torque of the hydraulic pump, and the control means adjusts the set torque of the hydraulic pump via the electromagnetic proportional valve. Provided is a power system controller for a construction machine that is provided.

  According to this configuration, the set torque of the hydraulic pump is adjusted by the control means controlling the electromagnetic proportional valve in accordance with the fluctuation of the battery voltage. In addition, since the set torque of the hydraulic pump is variably adjusted, it is possible to avoid restrictions on control near the upper limit / lower limit of the battery voltage.

  A third aspect of the present invention is the construction machine power system control according to the first or second aspect, wherein the control means is configured to decrease the engine speed when the set torque of the hydraulic pump is increased. Providing equipment.

  According to this configuration, when the set torque of the hydraulic pump is increased, the engine speed is decreased, so that the fuel efficiency of the engine is increased and noise is reduced.

  According to the first aspect of the present invention, since the fluctuation of the battery voltage is suppressed, the burden on the battery can be reduced and the life of the battery can be extended.

  According to the second aspect of the present invention, the set torque of the hydraulic pump can be adjusted by the control means controlling the electromagnetic proportional valve in accordance with the fluctuation of the battery voltage. Therefore, in addition to the effect of the first aspect, the set torque The adjustment operation becomes easy. In addition, since it is possible to avoid restrictions on control near the upper limit / lower limit of the battery voltage, a reduction in fuel efficiency at the upper limit of the voltage, which is a problem in the conventional device, and assist at the lower limit of the voltage. The problem of not being able to solve each can be solved.

  According to the third aspect of the present invention, when the set torque of the hydraulic pump is increased, the engine speed is also decreased. Therefore, in addition to the effect of the first or second aspect, the fuel efficiency of the engine is increased and the noise is also decreased. To do.

  In order to reduce the burden on the engine and the battery when rotating the generator, and to achieve the purpose of reducing the size and weight of the device, reducing the cost, and increasing the output, the battery voltage fluctuation is reduced. When the battery voltage rises, the torque assist motor is operated to increase the set torque of the hydraulic pump, and when the battery voltage drops, the generator is operated to generate electrical energy generated by the generator. There is provided a power system control device for a construction machine which is provided with a control means for controlling the battery so as to be stored in a battery so as to suppress fluctuations in the battery voltage.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 shows a hydraulic excavator as a construction machine to which the present invention is applied. In the hydraulic excavator 10, an upper swing body 13 is rotatably mounted on a lower traveling body 11 via a swing mechanism 12. The upper swing body 13 is provided with a cab 14 on one front side thereof, and a boom 15 is attached to the front center portion so as to be able to be raised and lowered. An arm 16 is attached to the tip of the boom 15 so as to be rotatable up and down, and a bucket 17 is attached to the tip of the arm 16.

  FIG. 2 is a block diagram showing a schematic configuration of a power system applicable to the hydraulic excavator shown in FIG. In FIG. 2, the power system of this embodiment includes an engine 21 for driving a hydraulic excavator, an electric / generator 22 and a hydraulic pump 23 connected to the power line of the engine 21, a control means 24, a battery, 25, an electromagnetic proportional valve 30, and an actuator 31.

  The engine 21 is a diesel engine in the present embodiment, and the excavator 10 travels using the engine 21 as a drive source. The hydraulic pump 23 is also driven by the engine 21.

  The electric / generator 22 receives a function of a generator that converts mechanical energy rotated by the engine 21 into electric energy and stores the electric energy in the battery 25, and receives electric energy from the battery 25. It has a function as an electric motor that converts the energy to drive the hydraulic pump 23, and has a structure in which the electric motor and the generator are combined in one housing.

  The hydraulic pump 23 drives an actuator (not shown) including hydraulic cylinders that operate the boom 15, the arm 16, and the bucket 17, and receives the driving force of the engine 21 and the driving force of the electric / generator 22. Works.

  The control means 24 includes a sensor 26, a limiter circuit 27, an inverter circuit 28, and a control circuit 29.

  The sensor 26 is a sensor that detects voltage fluctuation of the battery 25, and outputs a signal corresponding to the battery voltage to the control circuit 29.

  The limiter circuit 27 is a circuit that selectively switches between the function of the motor and the function of the generator that the motor / generator 22 has. When the electric motor / generator 22 is switched to the electric motor mode by the operation of the limiter circuit 27, the electric energy stored in the battery 25 is supplied to the electric motor / generator 22. On the contrary, when the electric / generator 22 is switched to the generator mode, the electric / generator 22 is rotated by the surplus torque of the engine 21, electric energy is generated from the electric / generator 22, and the electric energy is supplied to the battery 25. This is stored in the battery 25.

  When the electric energy stored in the battery 25 is supplied to the electric motor / generator 22, the inverter circuit 28 converts the electric energy into AC power and supplies it, and conversely, the electric energy is generated by the electric motor / generator 22. It has a conversion function for converting the AC power thus converted into DC power and supplying it to the battery 25.

  The control circuit 29 is a microcomputer (commonly referred to as “microcomputer”), controls the operation of the motor / generator 22 via the limiter circuit 27 according to a preprogrammed procedure, and is proportional to the rotation of the engine 21 and the electromagnetic proportionality. The valve 30 and the limiter circuit 27 are controlled.

  The electromagnetic proportional valve 30 is for adjusting the set torque of the hydraulic pump 23.

  FIG. 3 is a flowchart showing an example of a control procedure programmed in the control circuit 29 in advance. Next, the operation of the power system controller shown in FIG. 2 will be described using the flowchart of FIG.

  First, the control circuit 29 determines whether the battery voltage Vt of the battery 25 is above or below the reference voltage Vs from the information on the battery voltage of the sensor 26 (step S1).

  For example, in the torque diagram of the hydraulic pump shown in FIG. 4, the reference voltage Vs here is a range in which a standard required torque region of the hydraulic pump 23 is surrounded by a curve ABCD. The curve A-B-C-D is used as the reference voltage Vs, and it is determined that the battery voltage is decreasing within the range of the curve A-B-C-D. It is determined that In FIG. 4, the vertical axis indicates the discharge pressure P of the hydraulic pump 23, and the horizontal axis indicates the displacement volume Q of the hydraulic pump. Further, the battery voltage drops when the motor / generator 22 is used as an assisting motor, rises when the motor / generator 22 is used as an assisting motor, and further, due to load fluctuations of the hydraulic excavator 10, assist and power generation. The ratio will change and change.

  When the battery voltage Vt is higher than the reference voltage Vs, the control circuit 29 switches the motor / generator 22 to the assist motor mode and slightly reduces the rotational speed of the engine 21 (step S2). That is, when the rotational speed of the engine 21 is reduced, the fuel efficiency of the engine 21 is increased and the noise is also reduced.

  On the other hand, when the battery voltage Vt is lower than the reference voltage Vs, the control circuit 29 switches to a mode in which the motor / generator 22 operates as a generator and controls the above-described restriction on the rotational speed of the engine 21, that is, the rotational speed. The state in which the vehicle is operated with the lowering of the pressure is solved (step S3).

  Further, the process returns from step S2 or step S3 to step S1, and thereafter this operation is repeated.

  Therefore, in the configuration of the present embodiment, when the battery voltage Vt is higher than the reference voltage Vs, the battery voltage is consumed by using the motor / generator 22 as the motor, and when the battery voltage Vt is decreasing, Since the battery voltage is accumulated for use in the machine, large fluctuations in the battery voltage can be suppressed. Thereby, the burden on the battery 25 is reduced and the battery life can be extended. In addition, since the electric motor / generator 22 in which the function of the electric motor and the function of the electric generator are integrated is used, it is not necessary to prepare the electric motor and the electric generator individually, and the apparatus is reduced in size, weight and cost. Can be reduced.

  In the structure of the above embodiment, the limiter circuit 27 is made variable, and the threshold value for switching the motor / generator 22 from the motor mode to the generator mode or from the generator mode to the motor mode is adjusted. You may make it do. In this way, if the variable type is adopted, it becomes possible to avoid restrictions on the control near the upper limit / lower limit of the battery voltage, and the reduction in fuel efficiency at the upper limit of the voltage, which has been a problem with conventional devices. In addition, problems such as inability to assist at the lower limit of the voltage can be solved.

  In addition, the present invention can be variously modified without departing from the spirit of the present invention, and the present invention naturally extends to the modified one.

The figure shows an embodiment of the present invention.
1 is an overall configuration diagram of a hydraulic excavator to which a construction machine power system control device according to the present invention is applied. The block diagram which shows schematic structure of the motive power system control apparatus in a hydraulic excavator same as the above. The flowchart which shows an example of the control procedure in the control circuit of a motive power system control apparatus same as the above. The figure explaining an example of the judgment characteristic of a torque characteristic of a hydraulic pump, and the rise / fall of a battery voltage.

Explanation of symbols

DESCRIPTION OF SYMBOLS 21 Engine 22 Electricity / generator 23 Hydraulic pump 24 Control means 25 Battery 26 Sensor 27 Limiter circuit 28 Inverter circuit 29 Control circuit

Claims (3)

An engine, a hydraulic pump connected to the power line of the engine, a generator driven by excess torque of the engine, a battery for storing electrical energy generated by the generator, and received from the battery In a power system controller for a construction machine comprising a torque assisting electric motor that converts electric energy into mechanical energy and supplies the hydraulic pump to the hydraulic pump.
Detecting voltage fluctuation of the battery, when the battery voltage rises, operate the torque assisting motor to increase the set torque of the hydraulic pump, and when the battery voltage falls, operate the generator A control system for a construction machine, comprising control means for controlling the electric energy generated in such a manner as to be stored in the battery so as to suppress fluctuations in the battery voltage.   2. The hydraulic pump has an electromagnetic proportional valve for adjusting a set torque of the hydraulic pump, and the control means adjusts a set torque of the hydraulic pump via the electromagnetic proportional valve. Power system controller for construction machinery.   The construction system power system control device according to claim 1 or 2, wherein the control means is configured to decrease the engine speed when the set torque of the hydraulic pump is increased.

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