Hydraulic control valve for construction machinery

It is addressed to provide a hydraulic control valve for preventing high-speed rotation of a valve body of a check valve incorporated in the hydraulic control valve of a type that pressure oil is supplied from a tandem, path and a parallel path via the check valve. A check valve unit is constituted by a main unit and a valve body of a first check valve. A throttle is provided on a right side of an O-ring groove. On a main unit side, there is formed a cylindrical housing portion in which a threaded portion is formed on an outer peripheral portion for fixation to a casing of the hydraulic control valve. On an inner peripheral surface of the housing portion, a groove is formed in an axial direction. Meanwhile, the valve body of the first check valve has a rib. At a time of assembly, the rib, is inserted into the groove of the main unit as indicated by an arrow. After the valve body is assembled to the main unit and fixed to the casing, even with imbalance such as phase shift of the pressure-oil path, the rib having fit into the groove, namely the valve body, is prevented to rotate while it is slidable in the axial direction. Thus, the casing of a seating part of the valve body is not abraded.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a hydraulic control valve used for construction machinery such as a hydraulic shovel, and more particularly, to structure of a check valve incorporated in the hydraulic control valve.

2. Description of the Related Art

Construction machinery, for example, a hydraulic shovel normally comprises hydraulic cylinders for driving a boom, an arm, a shovel, and the like, and hydraulic motors for driving a swivel base, a travelling caterpillar, or a vehicle. To each of the hydraulic actuators, a required pressure oil is supplied from hydraulic pumps via each of hydraulic control valves of a control valve unit mounted on the swivel base.

Incidentally, as illustrated in FIG. 1 of JP 2002-155903 A (hereinafter, referred to as Patent Document 1), the control valve unit is provided with switching valves k1, k2, and k3connected in tandem via a center bypass path34. The switching valves k2and k3are provided with check valves via a parallel line32. Further, on a downstream side of each of the check valves, each of the switching valves k2and k3is provided with another check valve provided between each of the check valves and the center bypass path34.

FIG. 2of the present application refers to a control valve6which is a hydraulic circuit part of FIG. 1 of the Patent Document 1 described above, and simply illustrates only a part relevant to the invention of the present application. Note that, in the following description, a component corresponding to the switching valve in the Patent Document 1 is referred to as a hydraulic control valve, and a component corresponding to the control valve therein is referred to as a control valve unit.

InFIG. 2, three hydraulic control valves VL1to VL3are connected in tandem to each other. Apart of pressure oil delivered from a variable delivery pump VPM is provided to the tandem path2, another part thereof passes a bypass path1, a throttle3and a check valve5and, merges with the part of pressure oil having passed a check valve4in parallel provided in a path branched from the tandem path2, with the result of being fed to a port PT2of the hydraulic control valve VL2. The hydraulic control valve VL3has the similar circuit configuration.

The configuration ofFIG. 2enables simultaneously driving of a low-load hydraulic actuator and a high-load hydraulic actuator. The throttle3is adjusted in accordance with a magnitude of a load. Further, the check valve4prevents backflow into the tandem path2, and the check valve5prevents backflow into a parallel path1.

FIG. 3illustrates a main part of the structure of the hydraulic control valve VL2. InFIG. 3, in the hydraulic control valve VL2, a spool Spr is arranged in a hole passing though the inside of its casing CS. Reference symbols a and b shows pressure-oil ports for controlling the position of the spool Spr. Paths i and ii illustrated in the center of the figure constitute branch paths for supplying pressure oil supplied from the tandem path2or the bypass path1originally from a pump in accordance with the position of the spool Spr into ports APT or BPT. The branch operation of the pressure oil is performed by a check valve unit CH.

In the check valve unit CH, a main unit6thereof has an upper portion provided with the throttle3, a lower portion provided with an opening portion c, and an outer peripheral portion provided with a threaded portion d for attachment to the casing CS.

The opening portion c in the lower portion of the check valve unit CH houses the first check valve4facing the tandem path2and having a downward first valve body4aseating on a seating surface of the casing CS in the illustration, and the second check valve5having an upward second valve body5aslidably housed in the first check valve4. That is, in order to achieve compactification of structure as a hydraulic control valve, it has a constitution in which two check valves are coupled to each other.

Note that, each of the valve bodies4aand5aare urged downward and upward by springs (not shown).

As illustrated in the cross-section A-A, the first check valve4has an outer periphery substantially quadrangular in cross-section. Reference symbol4bbetween the first check valve4and the cylindrical lower portion of the check valve unit CH constitutes a path for leading the pressure oil from the bypass path1into the path i or ii.

However, the conventional structure illustrated inFIG. 3has the following problems.

That is, imbalance of a fluid force around the first check valve4causes the first check valve4to rotate at high speed due to a phase shift accompanying errors in machine processing on the throttle3or due to a flow-path shape on a downstream side of the first check valve4, further the first valve body4ais pressed against the seating surface of the casing CS, thus there has occurred a phenomenon that pressure oil passing through the path4babrades the casing itself. Since the casing CS is made of a cast metal and the valve body4ais made of a steel material, the abrasion progresses to a lower side inFIG. 3especially in a state in which an oil film on the seating surface has run out, and it may lead to a risk of destruction of a regular function as a hydraulic control valve. Further, the high-speed rotation of the first valve body4awastes energy of pressure oil, with the result that it may cause hydraulic oil to heat.

SUMMARY OF THE INVENTION

As a result of intensive studies, the inventors of the present invention have found out that those problems can be basically solved by preventing a rotation of the valve body of the first check valve.

Therefore, the present invention has an object to provide a hydraulic control valve for preventing high-speed rotation of a valve body of a check valve incorporated in the hydraulic control valve of a type that pressure oil is supplied from a tandem path and a parallel path via the check valve.

To achieve the object, a hydraulic control valve of the present invention is that for construction machinery for taking in pressure oil from one of a tandem path and a parallel path which are connected to a variable delivery pump, characterized in that:

a check valve unit is fixedly incorporated in a casing, the check valve unit slidably and unrotatably housing a valve body of a first check valve which operates so as to block communication with the tandem path in a state in which the pressure oil from the parallel path is supplied; and

a pressure-oil path from the parallel path is formed between an inner peripheral surface of the housing portion of the check valve unit and an outer peripheral surface of the valve body.

In the hydraulic control valve, as the check valve unit for unrotatably housing the valve body, a rib may be provided on a sliding direction on an outer surface of the valve body of the first check valve, the rib having a predetermined length; and a groove for receiving the rib may be formed on the inner peripheral surface of the housing portion of the check valve unit. Alternatively, it is possible that, as the check valve unit for unrotatably housing the valve body, a rib is provided on the inner peripheral surface of the housing portion of the check valve unit, the rib having a predetermined length, and a groove for receiving the rib is formed on an outer surface of the valve body of the first check valve.

Further, in these hydraulic control valves, the check valve unit may comprise a second check valve for blocking flux of the pressure oil from the parallel path into the pressure-oil path.

Still further, it is preferred to configure a valve body of the second check valve to be housed in the valve body of the first check valve.

According to the present invention, a check valve unit is fixedly incorporated in a casing, the check valve unit slidably and unrotatably housing a valve body of a first check valve which operates so as to block communication with the tandem path in a state in which the pressure oil from the parallel path is supplied, and a pressure-oil path from the parallel path is formed between an inner peripheral surface of the housing portion of the check valve unit and an outer peripheral surface of the valve body. Thus, even with imbalance of flow of pressure oil in the pressure-oil path and on a downstream side thereof, abrasion of the casing can be reduced as quickly as possible because the rotation of the valve body is prevented. Further, energy of pressure oil is not wasted, and heat is not generated in the hydraulic oil. Still further, synergistically with forming the pressure-oil path as described above, in the hydraulic control valve in which the check valve unit described above is incorporated, vibration, noise, or internal breakage does not occur because cavitation does not occur in the casing CS.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

In the following, detailed description is made of a preferred embodiment of the present invention with reference toFIG. 1.

FIG. 1is a perspective view of a check valve unit which is prior to assembly and to be incorporated in a casing of a hydraulic control valve according to the present invention. In the following description, elements corresponding to those illustrated inFIG. 3are denoted by the same reference symbols.

InFIG. 1, a check valve unit CH comprises a main unit6and a valve body4aof a first check valve4. An O-ring groove is denoted by reference symbol6a. A throttle is denoted by reference numeral3. A cylindrical housing portion is denoted by reference symbol6bwhich has an outer peripheral portion provided with a threaded portion d for fixing the main unit6to a casing CS of a hydraulic control valve VL2. An opening portion on an inner peripheral side of the housing portion6bis denoted by reference symbol c. On the inner peripheral surface of the housing portion6b, there is formed a groove8in an axial direction.

Meanwhile, the valve body4aof the first check valve4is provided with a rib7, a side wall4chaving a flat-surface shape so as to form a pressure-oil path4b, and a seating part4a3coming in contact with a seating surface of the casing CS when the check valve unit opens. When the valve body4ais assembled to the main unit6, the rib7is inserted into the groove8of the main unit6as indicated by an arrow. Fitting of the valve body4ainto the opening portion c of the main unit6causes the valve body4ato be assembled to the main unit6.

When the check valve unit closes, the seating part4a3of the valve body4aand the housing portion6bcome into contact. The side wall4cof the valve body4ais provided so as to allow pressure oil to pass. A section4a2is configured to be smaller in width than the opening portion c of the main unit6. The valve body4ais configured so as to be slidable in the main unit6. Further, a section4a1of the valve body4ais configured to be smaller in width than the section4a2, the section4a1being provided with the rib7. The section4a3is larger in width than the opening portion c of the main unit6. After the valve body4ais assembled to the main unit6and fixed to the casing CS, even with imbalance in the valve body4asuch as phase shift of the pressure-oil path4b, the rib7fitting into the groove8, namely, the valve body4ais prevented from being rotated while being slidable in the axial direction. Thus, also when the check valve unit opens and then the section4a3and the seating surface of the casing CS come into contact, the valve body4aof the first check valve4does not rotate, and hence the seating surface of the casing CS is not abraded. Further, energy of pressure oil is not wasted, and heat is not generated in hydraulic oil. Further, synergistically with the configuration which allows the pressure oil to pass as described above, in a hydraulic control valve in which the check valve unit as illustrated inFIG. 1is incorporated, cavitation does not occur in the casing CS. Thus, not only vibration and noise do not occur, but also internal breakage does not occur.

Hereinabove, description has been made of the preferred embodiment of the present invention. In this context, those skilled in the art may make various modifications on rotation-preventing means illustrated inFIG. 1. For example, the groove8and the rib7may be formed in multiple pairs at equal intervals on a circumference. Further, when the valve body4ahas a size which is capable of making the valve body4aslidable in the main unit6and allows the pressure oil to pass in the main unit6, for example, the width of the section4a1may be set to be equal to or larger than that of the section4a2.

Alternatively, as illustrated inFIG. 4, it is possible to configure such that a rib9is provided on an inner peripheral surface of the housing portion of the main unit6, and a groove10is provided in an outer surface of the valve body4a. In this case, when the valve body4ais assembled to the main unit6, the groove10is inserted into the rib9of the main unit6as indicated by an arrow. The side wall represented by reference symbol4chas a flat-surface shape so as to form the pressure-oil path4b. After the valve body4ais assembled to the main unit6and fixed to the casing CS, even with the imbalance in the valve body4asuch as phase shift of the pressure-oil path4h, the rib9fitting into the groove10, namely, the valve body4ais prevented from being rotated while being slidable in the axial direction. Thus, also when the check valve unit opens and then the seating portion of the valve body4aand the seating surface of the casing CS come into contact, the valve body4aof the first check valve4does not rotate, and hence the seating surface of the casing CS is not abraded. Further, energy of pressure oil is not wasted, and heat is not generated in hydraulic oil. Further, synergistically with the configuration which allows the pressure oil to pass as described above, also in a hydraulic control valve in which the check valve unit as illustrated inFIG. 4is incorporated, cavitation does not occur in the casing CS. Thus, not only vibration and noise do not occur, but also internal breakage does not occur.