Power plants – Pressure fluid source and motor – Having condition responsive control in a system of distinct...
Patent
1992-07-17
1994-05-31
Look, Edward K.
Power plants
Pressure fluid source and motor
Having condition responsive control in a system of distinct...
60452, 91446, 91518, F16D 3102
Patent
active
053158270
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an apparatus for switching the flow rate for attachments, and, more particularly, to an apparatus for switching the flow rate for attachments in order to supply hydraulic pressure for operating an attachment fastened to a hydraulic excavator according to the type of the attachment.
BACKGROUND ART
A hydraulic excavator composed of an upper revolving structure and a lower travelling structure has a multiplicity of hydraulic actuators such as hydraulic cylinders for moving a boom, an arm, a bucket and the like which constitute a working machine, and a travelling motor for rotating the right and the left tracks. In order to freely operate each of the actuators, two variable capacity type hydraulic pumps are usually mounted. As an alternative to the bucket fastened to serve as a working machine, an attachment such as a crasher or a hydraulic breaker or the like is sometimes fastened so as to perform an operation for crashing a structure or a rock. The aforesaid attachments respectively require different flow rates because the hydraulic devices for operating the attachments are different from one another. For example, a flow rate realized by two pumps is required in a case where a crasher is operated, while only a flow rate realized by one pump is required in a case where a hydraulic breaker is operated.
On the other hand, the above-mentioned attachments are usually used in such a manner that exchange of attachments for use in one hydraulic excavator is performed when the need arises. Therefore, the hydraulic excavator must be capable of easily switching the flow rate to be supplied to the attachment in order to be immediately adapted to the newly fastened attachment. Accordingly, in the conventional hydraulic excavator, a service valve 43 of two provided service valves 40 and 43 is, as shown in FIG. 6, switched so as to switch the flow rate between that realized by one main pump and that realized by two main pumps.
Referring to FIG. 6, five directional control valves for operating a revolving actuator, a boom-Hi actuator, a left-side service actuator, an arm-Lo actuator, and a left running actuator are connected in parallel to a variable capacity type hydraulic pump (hereinafter called a "main pump") 1. Five directional control valves for operating a right running actuator, a bucket actuator, a boom-Lo actuator, an arm-Hi actuator, and a right-side service actuator are connected in parallel to a main pump 5. Two pipes 41 and 42 connected to outlet ports of the right side service valve 40 are respectively connected to a hydraulic circuit extending from the left side service valve 43 to an actuator 19 so that they are joined together.
An attachment pedal 13 for operating the attachment is positioned in contact with a pilot-pressure control valve (hereinafter called a "PPC valve") 14, and a control pump 12 serves as a hydraulic pressure source for it. Two pilot circuits 44 and 45 extending from the PPC valve 14 are respectively connected to the left end portion and the right end portion of the service valve 43. Furthermore, branch circuits 46 and 47 are respectively provided for the two pilot circuits 44 and 45 and are respectively connected to the right end portion and the left end portion of the service valve 40 via pilot circuit directional control valves 48 and 49 having solenoids. The solenoids of the aforesaid pilot circuit direction control valves 48 and 49 are respectively connected to a selection switch 50.
In a case where, for example, a crasher is fastened as the attachment, a flow rate realized by two pumps is required in order to operate the crasher and therefore the selection switch 50 is switched on. As a result, the solenoids of the pilot circuit directional control valves 48 and 49 are excited, the branch circuits 46 and 47 of the pilot circuits 44 and 45 are thereby communicated, and the pilot pressure acts on the left end portion of the service valve 43 and the right end portion of the service valve 40 or acts on the right end portion of the s
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Imai Hiroshi
Ito Daigiro
Kabushiki Kaisha Komatsu Seisakusho
Look Edward K.
Nguyen Hoang
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