Flow control valve for construction equipment, having floating function

Disclosed is a hydraulic circuit for construction equipment, having a floating function for ground leveling work, which can be implemented by a main control valve. According to the present invention, provided is a flow control valve for construction equipment, having a floating function, comprising: a valve body having, formed therein, a supply path in communication with a pump path to which hydraulic oil is supplied from a hydraulic pump, and first and second actuator paths connected to a hydraulic cylinder driven by the hydraulic oil from the hydraulic pump; a spool switchably built into the valve body for, when switched, communicating the supply path into the first and second actuator paths so as to supply, to the hydraulic cylinder, the hydraulic oil from the hydraulic pump via the supply path and the first actuator path and return, to a tank path, the hydraulic oil discharged from the hydraulic cylinder via the second actuator path; a recycling path for supplying, to a small chamber of the hydraulic cylinder, a portion of the hydraulic oil returned from a large chamber of the hydraulic cylinder to the tank path and recycling the same; and a valve for floating conversion, installed at a predetermined position of the recycling path, wherein, in case of conversion to a floating state by application of pilot pressure to the valve for floating conversion, the large chamber and the small chamber of the hydraulic cylinder are communicated, and a path for supplying the hydraulic oil to the small chamber of the hydraulic cylinder and the recycling path are communicated so as to enable a bi-directional flow of the hydraulic oil.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a national phase entry under 35 U.S.C. § 371 of International Application No. PCT/KR2013/009785, filed Oct. 31, 2013, which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a flow control valve for construction equipment, and more particularly, to a flow control valve for construction equipment, in which a floating function for ground leveling work can be realized using a main control valve (MCV).

BACKGROUND ART

FIG. 1andFIG. 2are a hydraulic circuit diagram and a cross sectional view of a flow control valve for construction equipment having a floating function of the related art.

As illustrated inFIG. 1andFIG. 2, the flow control valve includes: a valve body7defining a supply passage communicating with a pump passage2through which working fluid is supplied from a hydraulic pump1and first and second actuator passages5and6connected to a hydraulic cylinder4actuated by working fluid supplied from the hydraulic pump1;

a spool9switchably disposed within the valve body7, wherein the spool9is switched to allow the supply passage3to communicate with the first or second actuator passage5or6, such that an amount of working fluid from the hydraulic pump1is supplied to the hydraulic cylinder4through the supply passage3and the first actuator passage5, and an amount of working fluid discharged from the hydraulic cylinder4returns to a tank passage8through the second actuator passage6;

a regeneration passage10through which a portion of working fluid returning to the tank passage8from a large chamber of the hydraulic cylinder4is supplied to a small chamber of the hydraulic cylinder4such that the portion of working fluid is regenerated;

a floating switching valve11including a logic valve11aconfigured to open and close a passage5abranched from the first actuator passage5, wherein the floating switching valve11is switched in response to a pilot pressure c applied thereto to drain working fluid from a back pressure chamber of the logic valve11athrough a control valve11band a drain line dr2, thereby opening the passage5a, such that, when a floating function of causing the large chamber and the small chamber of the hydraulic cylinder4to communicate with each other is selected, the large chamber and the small chamber of the hydraulic cylinder4communicate with each other, and a portion of working fluid from the large chamber and the small chamber communicating with each other is connected to a working fluid tank T; and

a logic valve12openably and closably disposed in the first actuator passage5to prevent a boom from moving downwardly due to contraction of the hydraulic cylinder4caused by an oil leakage.

A) A case of lifting the boom by actuating the hydraulic cylinder4will be described.

When the spool9is switched to the right on the drawing in response to a pilot pressure a being applied thereto, an amount of working fluid from the hydraulic pump1is supplied to the large chamber of the hydraulic cylinder4through sequentially, the pump passage2, the supply passage3, the spool9, the first actuator passage5, and the logic valve12. At this time, an amount of working fluid discharged from the small chamber of the hydraulic cylinder4returns to the working fluid tank T through sequentially, the second working fluid passage6, the spool9, and the tank passage8.

Thus, the stretching of the hydraulic cylinder4(a so called boom cylinder) can lift the boom (boom up).

B) A case of lowering the boom by actuating the hydraulic cylinder4will be described.

When the spool9is switched to the left on the drawing in response to a pilot pressure b applied thereto, an amount of working fluid from the hydraulic pump1is supplied to the small chamber of the hydraulic cylinder4through sequentially, the pump passage2, the supply passage3, the spool9, and the second actuator passage6.

At this time, a pilot pressure b1is applied to the control valve15, such that an amount of working fluid from the back pressure chamber12aof the logic valve12communicates with the first actuator passage5through the control valve15to open the logic valve12. Then, an amount of working fluid discharged from the large chamber of the hydraulic cylinder4returns to the working fluid tank T through sequentially, the logic valve12, the first actuator passage5, the spool9, the regeneration passage10, a booster valve13, and the tank passage8.

When the pressure of working fluid within the regeneration passage10is higher than the pressure within the second actuator passage6, a portion of working fluid in the regeneration passage10may merge with working fluid in the second actuator passage6through a check valve14disposed in the regeneration passage10, thereby being supplied to the small chamber of the hydraulic cylinder4.

Consequently, the contraction of the hydraulic cylinder4can lower the boom (boom down).

C) A case of performing a floating function will be described.

When a pilot pressure c is applied to the control valve11bof the floating switching valve11, the control valve11bis switched to the left on the drawing, an amount of working fluid drains from the back pressure chamber of the logic valve11athrough the control valve11band the drain line dr2. That is, when the control valve11bis switched, the large chamber and the small chamber of the hydraulic cylinder4communicate with each other, and a portion of working fluid within the communicating large and small chambers flows to the working fluid tank T.

Since separately from a main control valve (MCV) is provided a floating switching valve11, which provides a floating function allowing a bucket B to move along an irregular surface E to perform ground leveling work, as illustrated inFIG. 7, the number of parts increases, thereby increasing the manufacturing cost. In addition, since the floating switching valve11is additionally provided, the layout of equipment becomes complicated, and cost for the floating switching valve11is additionally caused, which are problematic.

DISCLOSURE

Technical Problem

Accordingly, the present invention has been made keeping in mind the above problems, and an object of the present invention is to provide a flow control valve for construction equipment, in which a floating function is realized using a main control valve (MCV) to simplify the layout of equipment and reduce the number of parts, thereby reducing the manufacturing cost.

Technical Solution

In order to achieve the above object, according to an embodiment of the present invention, a flow control valve for construction equipment having a floating function, includes:

a valve body defining a supply passage communicating with a pump passage through which working fluid is supplied from a hydraulic pump and first and second actuator passages connected to a hydraulic cylinder actuated by working fluid supplied from the hydraulic pump;

a spool switchably disposed within the valve body, wherein the spool is switched to allow the supply passage to communicate with the first or second actuator passage, such that working fluid from the hydraulic pump is supplied to the hydraulic cylinder through the supply passage and the first actuator passage, and working fluid discharged from the hydraulic cylinder returns to a tank passage through the second actuator passage;

a regeneration passage through which a portion of working fluid returning to the tank passage from a large chamber of the hydraulic cylinder is supplied to a small chamber of the hydraulic cylinder such that the portion of working fluid is regenerated;

a floating switching valve disposed in the regeneration passage, wherein the floating switching valve is switched to a floating position in response to a pilot pressure applied thereto, thereby causing the large chamber and the small chamber of the hydraulic cylinder to communicate with each other and causing the second actuator passage, through which working fluid is supplied to the small chamber of the hydraulic cylinder, and the regeneration passage to communicate with each other, such that an amount of working fluid is allowed to flow in both directions; and

a booster valve disposed in a passage between the regeneration passage and the tank passage, wherein the booster valve allows a portion of working fluid in the large chamber and the small chamber of the hydraulic cylinder to flow to the tank passage when the floating switching valve is switched to the floating position.

The floating switching valve may include:

a logic valve opening and closing the regeneration passage; and

a control valve disposed in a passage between a back pressure chamber of the logic valve and a working fluid tank, wherein, when the control valve is switched in response to the pilot pressure applied thereto to switch the floating switching valve to the floating position, working fluid drains from the back pressure chamber of the logic valve, thereby allowing an amount of working fluid to flow to the regeneration passage from the second actuator passage through which working fluid is supplied to the small chamber of the hydraulic cylinder.

A drain line, through which the working fluid drains from the back pressure chamber of the logic valve, may be connected to a port outside of the valve body.

A drain line, through which the working fluid drains from the back pressure chamber of the logic valve, may be connected to the tank passage within the valve body.

The flow control valve may further include a priority selection valve disposed upstream in the supply passage, wherein, when the floating switching valve is switched to the floating position, and the priority selection valve is switched in response to a pilot pressure applied thereto to perform a combined operation by actuating a hydraulic actuator other than the hydraulic cylinder, the priority selection valve supplies an amount of working fluid from the hydraulic pump to the other hydraulic actuator.

The floating switching valve may be disposed inside or outside of the valve body.

Advantageous Effects

According to the present invention configured as described above, a floating function is realized using the MCV. Since a separate floating switching valve is unnecessary, it is possible to simplify the layout of equipment and reduce the number of parts, thereby reducing the manufacturing cost.

DESCRIPTION OF THE REFERENCE NUMERALS IN THE DRAWINGS

BEST MODE

Hereinafter, some exemplary embodiments of a hydraulic circuit for construction equipment having a floating function according to the present invention will be described in detail with reference to the accompanying drawings.

FIG. 3is a hydraulic circuit diagram illustrating a flow control valve for construction equipment having a floating function according to a first embodiment of the present invention.FIG. 4is a cross sectional view illustrating the flow control valve for construction equipment having the floating function, illustrated inFIG. 3.FIG. 5is a hydraulic circuit diagram illustrating another flow control valve for construction equipment having a floating function according to a second embodiment of the present invention.FIG. 6is a view illustrating a key part of a drain line illustrated inFIG. 5.FIG. 7is a view illustrating a floating function according to some embodiments of the present invention.

Referring toFIG. 3andFIG. 4, the flow control valve for construction equipment having the floating function according to the first embodiment of the present invention includes:

a valve body7defining a supply passage3communicating with a pump passage2through which working fluid is supplied from a hydraulic pump1and first and second actuator passages5and6connected to a hydraulic cylinder4actuated by working fluid supplied from the hydraulic pump1;

a spool9switchably disposed within the valve body7, wherein the spool9is switched to allow the supply passage3to communicate with the first or second actuator passage5or6, such that working fluid from the hydraulic pump1is supplied to the hydraulic cylinder4through the supply passage3and the first actuator passage5, and working fluid discharged from the hydraulic cylinder4returns to a tank passage8through the second actuator passage6;

a regeneration passage10through which a portion of working fluid returning to the tank passage8from a large chamber of the hydraulic cylinder4is supplied to a small chamber of the hydraulic cylinder4such that the portion of working fluid is regenerated;

a floating switching valve16disposed at a location in the regeneration passage10, wherein the floating switching valve16is switched to a floating position in response to a pilot pressure d applied thereto, thereby causing the large chamber and the small chamber of the hydraulic cylinder4to communicate with each other and causing the second actuator passage, through which working fluid is supplied to the small chamber of the hydraulic cylinder4, and the regeneration passage10to communicate with each other such that an amount of working fluid can flow in both directions; and

a booster valve13disposed in a passage between the regeneration passage10and the tank passage8, wherein the booster valve13allows a portion of working fluid in the large chamber and the small chamber of the hydraulic cylinder4to flow to the tank passage8when the floating switching valve16is switched to the floating position.

The floating switching valve16includes:

a logic valve17opening and closing the regeneration passage10; and

a control valve18disposed in a passage between a back pressure chamber17aof the logic valve17and a working fluid tank T. When the control valve18is switched in response to the pilot pressure d applied thereto in order to switch the floating switching valve16to the floating position, working fluid may drain from the back pressure chamber17aof the logic valve17through the control valve18and a drain line dr3, thereby allowing an amount of working fluid to flow to the regeneration passage10from the second actuator passage6through which working fluid is supplied to the small chamber of the hydraulic cylinder4.

A drain line dr3, through which the working fluid drains from the back pressure chamber17aof the logic valve17, may be connected to a port outside of the valve body7.

A drain line dr3, through which the working fluid drains from the back pressure chamber17aof the logic valve17, may be connected to the tank passage8within the valve body7.

A priority selection valve20may be disposed upstream in the supply passage3. In the case in which the floating switching valve16is switched to the floating position, when the priority selection valve20is switched in response to a pilot pressure f applied thereto to perform a combined operation by actuating a hydraulic actuator (not shown) other than the hydraulic cylinder4, the priority selection valve20supplies an amount of working fluid from the hydraulic pump1to the other hydraulic actuator.

The floating switching valve16may be disposed inside or outside of the valve body7.

As described above, the configuration of lifting a boom by stretching the hydraulic cylinder4using an amount of working fluid supplied from the hydraulic pump1due to the switching of the spool9in response to a pilot pressure a applied thereto is the same as inFIG. 2, and a detailed description thereof will be omitted.

Hereinafter, a case of lowering the boom by actuating the hydraulic cylinder4will be described.

When the spool9is switched to the left on the drawing in response to a pilot pressure b applied thereto, an amount of working fluid from the hydraulic pump1is supplied to the small chamber of the hydraulic cylinder4through sequentially, the pump passage2, the supply passage3, the spool9, and the second actuator passage6.

Here, when a pilot pressure b1is applied to the control valve15, an amount of working fluid discharged from the back pressure chamber12aof the logic valve12communicates with the first actuator passage5through the control valve15, thereby opening the logic valve12. Then, an amount of working fluid discharged from the large chamber of the hydraulic cylinder4returns to the working fluid tank T through sequentially, the logic valve12, the first actuator passage5, the spool9, the regeneration passage10, the booster valve13, and the tank passage8.

In this case, when the pressure of working fluid within the regeneration passage10is higher than the pressure within the second actuator passage6, a portion of working fluid in the regeneration passage10may merge with working fluid in the second actuator passage6through the logic valve17disposed in the regeneration passage10, thereby being supplied to the small chamber of the hydraulic cylinder4.

Consequently, the contraction of the hydraulic cylinder4can lower the boom (boom down).

Hereinafter, a case of performing the floating function for ground leveling work will be described.

Specifically, in the position in which the boom is lowered by contracting the hydraulic cylinder4to perform ground leveling work, when a pilot pressure d is applied to the control valve18of the floating switching valve16, the spool of the control valve18is switched downwardly on the drawing ofFIG. 3, such that an amount of working fluid drains from the back pressure chamber17aof the logic valve17through the control valve18and the drain line dr3.

Consequently, the passage19through which the second actuator passage6communicates with the regeneration passage10is opened, thereby allowing working fluid to flow from the second actuator passage6to the regeneration passage10. That is, the large chamber and the small chamber of the hydraulic cylinder4communicate with each other, and a portion of working fluid from the large chamber and the small chamber of the hydraulic cylinder4communicating with each other is caused to flow to the working fluid tank T through sequentially, the booster valve13and the tank passage8.

As described above, the floating switching valve16for ground leveling work is provided and realized within the valve body7of a main control valve (MCV) A, thereby removing the problem in that the separate floating switching valve11(including the logic valve11aand the control valve15) is attached to the MCV A as inFIG. 1.

In addition, as illustrated inFIG. 5, a drain line dr4draining working fluid in the back pressure chamber17aof the logic valve17may be connected to the tank passage8in the valve body7. It is thereby possible to perform ground leveling work by allowing the large chamber and the small chamber of the hydraulic cylinder4to communicate with each other by switching the control valve18disposed in the passage19, through which the second actuator passage6communicates with the regeneration passage10, to an open position.

Furthermore, as illustrated inFIG. 5, in the position in which the floating function is selected, when a combined operation may be performed by driving a hydraulic actuator (not shown) other than the hydraulic cylinder4(a so-called boom cylinder), an amount of working fluid from the hydraulic pump1may be supplied to the other hydraulic actuator with priority to the hydraulic cylinder4.

That is, as the pilot pressure f applied to the control valve of the priority selection valve20disposed upstream in the supply passage switches the spool to the right on the drawing, an amount of working fluid supplied from the hydraulic pump1may apply pressure to the priority selection valve20, thereby closing the supply passage3. It is therefore possible to supply an amount of working fluid from the hydraulic pump1to the other hydraulic actuator with priority to the hydraulic cylinder4.

Although the specific exemplary embodiments of the present disclosure have been presented in the foregoing descriptions, many modifications and variations are obviously possible for a person having ordinary skill in the art without departing from the principle and scope of the present invention defined by the appended claims.

INDUSTRIAL APPLICABILITY

According to the present invention having the foregoing features, it is possible to realize a floating function using a MCV to simplify the layout of equipment and reduce the number of parts, thereby reducing the manufacturing cost.