Hybrid construction machine

Abstract

Provided is a hybrid construction machine capable of preventing overcharge of an electrical storage device, comprising: an engine; a generator-motor; a hydraulic pump; a hydraulic actuator to be operated by the hydraulic pump as a hydraulic pressure source; an actuator regeneration section to make a regenerative action of generating actuator regenerated-electric-power through return fluid from the hydraulic actuator; an electric storage device; a charging-rate detector; and a control section. The control section performs: causing the electric storage device to be charged with electric power generated by the generator action of the generator-motor and the actuator regenerated-electric-power generated by the regenerative action of the actuator regeneration section; causing the generator-motor to make a motor action through electric power stored in the electric storage device to assist the engine; and a regeneration control including stopping the generator action of the generator-motor and restricting the actuator regenerated-electric-power of the actuator regeneration section, when the charging-rate detector detects that the charging rate of the electric storage device is more than a preset charging-rate limitation value.

Description

technical field [0001] The present invention relates to a hybrid construction machine that utilizes return oil from a hydraulic actuator such as a boom hydraulic cylinder for regeneration. Background technique [0002] by Figure 7 An excavator is shown as an example to illustrate the background of the invention. [0003] The excavator includes: a crawler-type lower walking body 1; an upper rotating body 2, which is freely mounted on the lower walking body 1 by rotating around an axis O perpendicular to the ground; an attachment AT installed on the upper rotating body 2; ; and a hydraulic pump driven by the engine. The attachment AT includes: a boom 3 , an arm 4 , a bucket 5 , and a plurality of hydraulic actuators for making them work, that is, a boom hydraulic cylinder 6 , an arm hydraulic cylinder 7 , and a bucket hydraulic cylinder 8 . The lower traveling body 1 is driven by a traveling drive device using a traveling hydraulic motor as a drive source, and the upper rev...

AI Technical Summary

Problems solved by technology

[0007] In the above-mentioned known technology, if the regenerative action is performed using the return oil from the hydraulic actuator in a state where the charge rate of the electrical storage device is high, the electrical storage device is charged to more than Appropriate charging rate, that is, overcharging, which may lead to failure or shortening of the life of the power storage device

especially in such Figure 7 During the lowering operation of the boom 3 of the excavator shown, large regenerative power is generated by flowing return oil from the boom hydraulic cylinder 6 at a large flow rate, that is, boom lowering regenerative power, so the possibility of overcharging increases.

In addition, in the construction machinery that performs both the regenerative function when turning and the regenerative function when the boom is lowered, when the compound operation of turning and lowering the boom that performs both regenerative functions at the same time, not only the possibility of overcharging is further increased , and there is a concern that the slewing braking performance will be reduced because the slewing energy cannot be fully regenerated

[0008] As a method of preventing the above-mentioned overcharging, it is known to use a regenerative resistor to consume the excess part of the regenerative power, but discarding the generated regenerative power as heat in this way will cause energy loss, and a relatively large resistor for consuming the regenerative power is required as a The regenerative resistor and the control device of the regenerative resistor need to add special equipment including equipment for processing the heat generated by the regenerative resistor

This makes it difficult to arrange equipment in an excavator where space constraints are particularly severe, and leads to a significant increase in costs

If a large-capacity power storage device that does not easily overcharge is used, the same disadvantages as above will be caused in terms of cost and installation space.

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