JP4012885B2 - Power source device for work machines - Google Patents

Description

  The present invention relates to a power source device for a hybrid work machine that uses both engine power and electric power.

  In a hybrid work machine, for example, a hydraulic pump and a generator are driven in parallel by an engine, and a hydraulic actuator is driven by a hydraulic pump. On the other hand, an electric motor includes a generator and a power storage device charged by the output of the generator. The structure which drives etc. is taken.

  Alternatively, a configuration is adopted in which a generator is driven by an engine, a motor is rotated by the power generated by the generator and the power stored in the power storage device, and the hydraulic pump is driven by the motor (see Patent Documents 1 and 2).

  In addition, as the power storage device, a capacitor (usually an electric double layer capacitor is used) serving as a power source for a drive system such as a work device or a traveling device, and a power source for an auxiliary system such as a control device or electrical equipment And an auxiliary power storage device (usually a secondary battery is used) are known.

The above capacitor has a feature that it has a much longer life than a secondary battery such as a lead storage battery, a nickel metal hydride battery, or a lithium ion battery, and is a main power storage device for a work machine that repeatedly charges and discharges like an excavator. Suitable as
JP 2000-283107 A Japanese Patent Laid-Open No. 10-42587

  On the other hand, the weak point of the capacitor is that it deteriorates severely when full charge (float) or a state close to it (hereinafter referred to as full charge state) continues, and this deterioration causes a decrease in capacitance (decrease in energy density). As a result, an increase in internal resistance (decrease in output density) occurs, and the lifetime inherent in the capacitor decreases.

  In this regard, in the conventional hybrid work machine, although the charge amount (voltage) of the capacitor varies depending on the charge / discharge state with respect to the work load immediately before the end of the work, for example, the light load state continues and the capacitor is fully charged. When the work is completed and left until the next day, there is a problem that the life of the capacitor is shortened.

  As a countermeasure, it is conceivable to suppress the charge amount of the capacitor to a level less than full charge during the work (stop charging at a set value). In this case, the engine output is reduced or the engine is stopped and power is supplied from the capacitor to the load. In the former case, the engine efficiency is lowered, and in the latter case, the engine stop / start frequency is increased and the system is increased. As a result.

  Therefore, the present invention provides a power source device for a work machine that can avoid a full charge state of a capacitor from continuing for a long time and can effectively use energy.

  The invention according to claim 1 includes an engine, a generator driven by the engine, a capacitor as a main power storage device, and an auxiliary power storage device, and stores the generator output in the capacitor and the auxiliary power storage device. The power source device of the constructed work machine includes work end detection means for detecting the end of work of the machine, capacitor charge amount detection means for detecting the charge amount of the capacitor, and charge control means, and this charge control means. Is detected from the capacitor when the end of the work is detected by the work end detection means, and the charge amount of the capacitor detected by the capacitor charge amount detection means at this time is higher than a predetermined discharge set value. It is configured to perform discharge control for discharging toward the auxiliary power storage device.

  According to a second aspect of the present invention, in the configuration of the first aspect, the charge control means limits the amount of charge of the auxiliary power storage device to a first charge set value that is smaller than a rated value during work, and performs the discharge control. It is sometimes configured to increase the second charge set value higher than the first charge set value.

  According to the present invention, when the charge amount of the capacitor exceeds the discharge set value at the end of the work, the excess amount is discharged from the capacitor toward the auxiliary power storage device.

  For this reason, by setting the discharge set value as the amount of charge that does not reach the fully charged state, it is possible to avoid a situation where the battery is left in the fully charged state, thereby preventing the deterioration of the capacitor.

  In addition, since the capacitor's charging operation itself is not suppressed, but the extra power of the capacitor is transferred to the auxiliary power storage device, it is possible to operate with high system efficiency while maximizing the capacity of the capacitor.

  By the way, if the auxiliary power storage device is fully charged at the end of the work, the capacitor is not discharged to the auxiliary power storage device, and the intended purpose cannot be achieved.

  In this respect, according to the second aspect of the invention, the amount of charge of the auxiliary power storage device is limited to the first charge setting value smaller than the rated value during the work to secure the free space, and at the end of the work (during the discharge control) ) Is increased to a second charge set value higher than the first set value, and the discharge amount from the capacitor is accepted by the free capacity, so that the capacitor discharge action at the end of the work can be ensured.

  FIG. 1 shows a block configuration of a drive system and a control system of a work machine (for example, an excavator) according to the embodiment.

  In the figure, an engine 1 as a power source is connected in parallel with a hydraulic pump 3 via a power device 2 and a generator / motor 4 that performs a generator action and a motor action in one unit. Driven.

  The hydraulic pump 3 is connected to hydraulic actuators for working devices (both not shown) via control valves, and these hydraulic actuators are driven by the pressure oil supplied from the hydraulic pump 3.

  On the other hand, the generator / motor 4 is connected to a capacitor (usually a double-layer capacitor) 6 as a main power storage device via a controller 5 including a rectifier, a converter, and the like, and the capacitor 6 drives a working motor and the like. Electric power (for example, 300V) is supplied to the system.

  Further, an auxiliary battery (for example, a lead storage battery) 8 as an auxiliary power storage device is connected to the controller 5 via a power conversion device 7, and electric power (from the auxiliary battery 8 to auxiliary equipment such as work lights and electrical components ( For example, 24V) is supplied.

  The capacitor 6 and the auxiliary battery 8 are respectively provided with voltage sensors 9 and 10 as charge amount detection means, and both voltages (charge amounts) detected by the voltage sensors 9 and 10 are sent to the charge control device 11.

  Further, an engine key switch 12 as a work end detection means is connected to the charge control device 11, and when the switch 12 is turned off, the signal is sent to the charge control device 11 as a work end signal.

  In this charging control device 11, for the charging voltage of the auxiliary battery 8, for example, a charging voltage corresponding to about 80% of the rated voltage (first charging set value) Vlower and a charging voltage corresponding to the rated voltage or a value close thereto (second charging) Setting value) Vupper is set, and one of these two types of setting values Vlower and Vupper is selected and sent to the power converter 7 as a command for the auxiliary battery charging voltage, depending on when the work is performed and when the work is finished.

  In the charging control device 11, a voltage (discharge setting value) Vcd to start discharging the capacitor 6 is set by the discharge voltage setting means 13, and when the capacitor voltage Vc is higher than the discharge start voltage Vcd at the end of work, A charge switching command for transferring the electric power of the capacitor 6 to the auxiliary battery 8 is issued from the charge control device 11 to the power conversion device 7.

  That is, the charge control device 11, the power conversion device 7, and the discharge voltage setting device 13 constitute a charge control device, and this charge control device avoids a situation where the capacitor 6 is left in an overcharged state after the work is completed. Control is performed.

  The contents of this control will be described in detail with reference to the flowchart of FIG.

  Along with the start of control, auxiliary battery charge voltages (first and second charge setting values) Vlower and Vupper at the time of work and at the end of work (during discharge control) are set (step S1).

  In step S2, it is determined whether or not the work is finished. When the work is in progress (in the case of NO), the charge control device 11 instructs the power conversion device 7 to set the auxiliary battery charge voltage to the first charge set value Vlower. Is issued (step S3).

  Thereby, the auxiliary battery 8 is charged with the first charging set value Vlower as the upper limit. For this reason, the free capacity for accepting the discharge power from the capacitor 6 at the end of the work is secured in the auxiliary battery 8.

  On the other hand, if it is determined in step S2 that the work is finished (in the case of YES), the set capacitor discharge start voltage Vcd and the capacitor voltage Vc are detected in step S4, and then the capacitor discharge start voltage in step S5. Vcd and capacitor voltage Vc are compared.

  If YES here (when Vc <Vcd), the capacitor 6 is not fully charged and it is not necessary to discharge the capacitor 6, so the control ends.

  On the other hand, in the case of NO (when Vc ≧ Vcd), the capacitor 6 is in a fully charged state, so that discharging is required, and the auxiliary battery charging voltage is set to the second charging setting from the charging control device 11 to the power conversion device 7. A charge switching command is issued to raise the value Vupper.

  As a result, discharging from the capacitor 6 toward the auxiliary battery 8 is performed.

  This discharging action is performed until Vc <Vcd (Vlower and Vupper are set so that the auxiliary battery voltage does not reach Vupper during this time).

  As described above, when the voltage (charge amount) Vc of the capacitor 6 is higher than the discharge start voltage (discharge set value) Vcd at the end of the work, the power exceeding the discharge start voltage Vcd is transferred from the capacitor 6 to the auxiliary battery 8. Since the discharge start voltage Vcd is set to a value that does not cause the capacitor 6 to be fully charged, the capacitor 6 can be prevented from being left in an overcharged state after the work is completed. . For this reason, deterioration of the capacitor 6 can be prevented and its original life can be secured.

  Moreover, instead of suppressing the charging operation itself of the capacitor 6, the extra power (overcharged amount) of the capacitor 6 is transferred to the auxiliary battery 8, so that the capacity of the capacitor 6 is utilized to the maximum while operating with high system efficiency. can do.

  In addition, the charging voltage of the auxiliary battery 8 is limited to a value equal to or lower than the first charging set value Vlower that is lower than the rated value at the time of work to secure an empty capacity in the auxiliary battery 8, and the first time at the end of work (during discharge control) Since the discharge amount from the capacitor 6 is received by the above-mentioned free capacity by raising the second charge set value Vupper higher than the charge set value Vlower, it is possible to ensure the discharging action of the capacitor 6 at the end of the operation.

  By the way, in the environment where a margin for receiving discharge of the capacitor 6 by the auxiliary battery 8 is ensured, such as when a plurality of auxiliary batteries 8 are provided, it is not always necessary to regulate the charge amount of the auxiliary battery 8 during work.

  In the above embodiment, the generator 1 and the motor 4 are driven by the engine 1 and the engine 1 is assisted by the motor action of the generator and motor 4 when the engine load is high. It may be provided separately.

  Further, the present invention is not limited to a hybrid work machine that adopts a so-called parallel system in which the hydraulic pump and the generator are driven in parallel by the engine as described in the above embodiment, and the generator is driven by the engine, The present invention can also be applied to a hybrid work machine that employs a so-called series system in which a hydraulic pump is driven by rotating an electric motor.

It is a block block diagram of the drive system and control system of the working machine concerning embodiment of this invention. It is a flowchart for demonstrating the effect | action of embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Engine 2 Power divider 3 Hydraulic pump 4 Generator / motor 6 Capacitor 8 Auxiliary battery 7 Power conversion apparatus which comprises charge control means 11 Same as above, Charge control apparatus 13 Same as above, Discharge voltage setting means

Claims (2)

  Power of a working machine comprising an engine, a generator driven by the engine, a capacitor as a main power storage device, and an auxiliary power storage device, and configured to store the generator output in the capacitor and the auxiliary power storage device The power source apparatus includes work end detection means for detecting the end of work of the machine, capacitor charge amount detection means for detecting the charge amount of the capacitor, and charge control means. The charge control means includes the work end detection means. When the end of work is detected by the capacitor and the charge amount of the capacitor detected by the capacitor charge amount detection means is higher than a predetermined discharge set value at this time, the capacitor discharges toward the auxiliary power storage device. A power source device for a work machine, characterized in that the discharge control is performed.   2. The power source device for a work machine according to claim 1, wherein the charge control unit limits a charge amount of the auxiliary power storage device to a first charge set value smaller than a rated value during work, and during the discharge control. A power source device for a working machine, characterized in that the power source device is configured to be raised to a second charge setting value higher than the first charge setting value.

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