Control valve

Abstract

This control valve is provided with: a housing having a high-pressure passage which is in communication with a hydraulic pressure supply source, a low-pressure passage which is in communication with a tank for storing hydraulic fluid, a cylinder passage which is in communication with a hydraulic actuator, and a sleeve which is connected to the high-pressure passage, the low-pressure passage, and the cylinder passage; a lift lock poppet valve provided within the cylinder passage, the lift lock poppet valve being capable of taking an open position at which the lift lock poppet valve connects the sleeve and the hydraulic actuator, the lift lock poppet valve being also capable of taking a closed position at which the lift lock poppet valve blocks the communication between the sleeve and the hydraulic actuator, the lift lock poppet valve having a poppet valve body having a back-pressure chamber therein; a back-pressure passage for connecting the low-pressure passage and the back-pressure chamber of the poppet valve body and having a solenoid valve provided between the ends of the back-pressure passage; and an emergency operation valve having an emergency operation valve body provided movable forward and backward between a use position at which the emergency operation valve body presses the poppet valve body, and a retracted position at which the emergency operation valve body is separated from the poppet valve body, the emergency operation valve body being seated on a valve seat when located at the retracted position, thereby providing mechanical sealing.

Description

technical field [0001] The present invention relates to a control valve used in a hydraulic circuit of an industrial vehicle or the like. Background technique [0002] As an example of a control valve widely mounted on industrial vehicles including stackers and used, the types shown below are exemplified. [0003] The control valve constitutes a hydraulic circuit for supplying operating hydraulic pressure to the cylinder head 2a side of the hydraulic brake 2 that drives the lift L, which is a driving object. like Figure 4 and Figure 5 As shown, the control valve includes a housing 1, a spool valve body 3 that can move forward and backward inside a sleeve 1e provided in the housing 1, and a lift-lock poppet valve built in the housing 1 4. [0004] The casing 1 includes: a high-pressure passage 1a that communicates with a pump P serving as a hydraulic supply source, a low-pressure passage 1b that communicates with a tank T for storing hydraulic fluid, and a cylinder passa...

AI Technical Summary

Problems solved by technology

However, when the former is used, a gap to the extent that the O-ring is prevented from being exposed and the emergency operation valve body can slide must be formed between the emergency operation valve body and the emergency valve plug, which causes another problem requiring high machining accuracy.

Furthermore, when the latter is adopted, since not only the O-ring but also the backup ring are provided separately, new problems arise such as an increase in the number of parts and an accompanying increase in manufacturing work.

[0014] The above-mentioned problems are also caused by the configuration of providing a working fluid discharge passage that directly connects the back pressure chamber and the short pipe.

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