JP2007078131A - Hydraulic control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hydraulic control device simplified in structure, reduced in size, reduced in number of man-hours for assembling and parts, and having a low cost hydraulic check valve by improving the internal structure of the hydraulic check valve so that the same functions thereof as those of a conventional shuttle valve can be developed to eliminate the conventional shuttle valve. <P>SOLUTION: This hydraulic control device comprises the hydraulic check valve. In the hydraulic check valve, a sleeve is secured to the inner peripheral surface of a housing. A piston moving due to a pressure difference between two hydraulic oil chambers of a hydraulic cylinder is reciprocably fitted to the inner peripheral surface of the sleeve. The hydraulic control device further comprises two oil chambers demarcated by the piston and connected to two oil passages through open/close valves. Two small holes connecting the two oil chambers to a load hydraulic pressure detection passage are formed in the sleeve. The two small holes are opened and closed by the movement of the piston due to a difference in load hydraulic pressure between the two hydraulic pressure chambers. The two oil chambers are communicated with or cut off the load hydraulic pressure detection passage. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is applied to a forklift cargo handling operation or traveling hydraulic control device, a construction machine excavation operation or traveling hydraulic control device, and the like, and supplies, discharges, and position control of hydraulic oil to the hydraulic cylinder for operation or traveling control. A hydraulic check valve that detects a change in the load hydraulic pressure of the hydraulic cylinder is provided in the hydraulic oil passage that connects to the control valve to perform, and the load hydraulic pressure is controlled to the target hydraulic pressure by the pressure control valve based on the detected value of the load hydraulic pressure from the hydraulic check valve The present invention relates to a hydraulic control device configured to do this.

  A hydraulic cargo handling work device for a forklift is provided with a hydraulic oil outlet of a control valve in a hydraulic oil path between a hydraulic cylinder for cargo handling work and a control valve for supplying, discharging, and controlling the position of hydraulic oil to the hydraulic cylinder. And a hydraulic control device provided with a hydraulic check valve for opening and closing two oil passages to the two hydraulic oil chambers of the hydraulic cylinder and detecting a change in load hydraulic pressure of the hydraulic cylinder.

FIG. 5 shows a conventional example of a hydraulic control apparatus for a forklift hydraulic load handling apparatus including such a hydraulic check valve.
In FIG. 5, reference numeral 103 denotes a hydraulic cylinder, which includes two hydraulic oil chambers 103a and 103b, and a cargo handling work device is connected to an output end thereof. 100 is a hydraulic pressure check valve which will be described in detail later, 104 is a hydraulic pump driven by an engine (not shown), 105 is a load hydraulic pressure on the hydraulic cylinder 103 side is controlled to a target hydraulic pressure based on a detected load hydraulic pressure value from the hydraulic pressure check valve 100 A pressure control valve 107, a pressure regulating valve 107 for regulating the maximum hydraulic pressure of the hydraulic operation system, and an oil tank 106.
A control valve 101 is driven by solenoids 101a and 101b, and supplies and discharges hydraulic oil to and from the hydraulic cylinder 103 and controls the position. The two hydraulic oil passages 124 and 125 from the control valve 101 are connected to the control valve 101. It is connected to the two hydraulic oil chambers 103 a and 103 b of the hydraulic cylinder 103 via the hydraulic check valve 100.

100 is a hydraulic check valve, 1 is a housing of the hydraulic check valve 100, 9a and 9b are outlet oil passages formed in the housing 1, and an outlet port A of the outlet oil passage 9a is hydraulic oil of the hydraulic cylinder 103. The outlet port B of the outlet oil passage 9 b is connected to the hydraulic oil chamber 103 b of the hydraulic cylinder 103. Reference numerals 11a and 11b denote inlet oil passages connected to the hydraulic oil passages 124 and 125 from the control valve 101, respectively.
A piston 4 is fitted in the housing 1 so as to be reciprocally slidable. Two oil chambers 7a and 7b are defined on both sides of the piston 4 by the piston 4, and the two oil chambers 7a and 7b are The inlet oil passages 11a and 11b are connected via passage holes 8a and 8b drilled in valve cases 2a and 2b, which will be described later.
2a and 2b are valve cases fixed in the housing 1, and 6a and 6b are slidably fitted in the valve cases 2a and 2b so that the oil chambers 7a and 7b and the outlet oil passages 9a and 9b It is an on-off valve that opens and closes. Reference numerals 5a and 5b denote springs for returning the on-off valves 6a and 6b.

Reference numeral 120 denotes a shuttle valve incorporated in the housing 1. The shuttle valve 120 includes a valve hole 120a formed in the housing 1, a valve body 123 fitted in the valve hole 120a so as to be slidable back and forth, and two oil chambers facing both surfaces of the valve body 123. The two oil chambers 121 and 122 are connected to hydraulic fluid passages 124 and 125 from the control valve 101, respectively, so that one hydraulic fluid passage (for example, hydraulic fluid) from the control valve 101 is formed. When hydraulic oil is sent to the passage 124), the hydraulic pressure is introduced into one oil chamber (for example, the oil chamber 121) and the valve body 123 is moved to the left in FIG. 12 is opened, and this detected load hydraulic pressure is sent to the pressure control valve 105 through the load hydraulic pressure detection circuit 13.
Reference numeral 108 denotes a check valve provided for each hydraulic pressure check valve 100 in the load hydraulic pressure detection circuit 13 for a plurality of hydraulic pressure check valves 100.

  Further, Patent Document 1 (Japanese Patent Laid-Open No. 7-190006) discloses a pressure compensation type in which each actuator can be reliably operated without breaking the relative balance of each actuator even when the discharge amount of the hydraulic pump is insufficient. A hydraulic control device is disclosed.

JP-A-7-190006

In the conventional hydraulic check valve 100 shown in FIG. 5, when one side of the two oil chambers 7a and 7b formed by the piston 4 is pressurized, the pressure in the other oil chamber is released and two oil chambers are released. A shuttle valve 120 for communicating or blocking between the chambers 7 a and 7 b and the load hydraulic pressure detection passage 13 is separately manufactured and configured to be incorporated in the housing 1 of the hydraulic check valve 100.
For this reason, in such a conventional technique, the structure of the hydraulic check valve 100 is complicated and large, and the number of parts is increased. Furthermore, the number of assembly steps for assembling the separately manufactured shuttle valve 120 in the housing 1 is increased. This increases the manufacturing cost of the shuttle valve 120.
Have problems such as.
Note that Patent Document 1 is a pressure-compensated hydraulic control device that avoids a decrease in the supply hydraulic pressure on the hydraulic pump side with respect to the required working hydraulic pressure on the load side, but does not include an equivalent to a hydraulic check valve.

  In view of the problems of the prior art, the present invention improves the internal structure of the hydraulic check valve so that it can perform the same function as the conventional shuttle valve, thereby omitting the conventional shuttle valve and simplifying and miniaturizing the structure. It is an object of the present invention to provide a hydraulic control device that is compact, has a reduced number of assembly steps and parts, and includes a low-cost hydraulic check valve.

  The present invention achieves such an object, and a hydraulic oil outlet of the control valve is connected to a hydraulic oil passage connecting a hydraulic cylinder and a control valve for supplying, discharging, and controlling the position of the hydraulic oil to the hydraulic cylinder. A hydraulic check valve is provided for opening and closing two oil passages to the two hydraulic oil chambers of the hydraulic cylinder and detecting a change in the load hydraulic pressure of the hydraulic cylinder, and the load hydraulic pressure detection value from the hydraulic check valve is used as a pressure control valve. In the hydraulic control apparatus configured to control the load hydraulic pressure to the target hydraulic pressure based on the detected value of the load hydraulic pressure by the pressure control valve, the hydraulic check valve fixes a sleeve to the inner peripheral surface of the housing. A piston that moves due to a pressure difference between the two hydraulic oil chambers of the hydraulic cylinder is fitted to the inner peripheral surface of the sleeve so as to be reciprocally slidable. Two oil chambers respectively connected to the two oil passages via open / close valves, and drilling two small holes respectively connecting the two oil chambers and the load oil pressure detection passage to the sleeve, The two small holes are opened and closed by the movement of the piston in accordance with the difference in load oil pressure between the two hydraulic oil chambers of the hydraulic cylinder, and the two oil chambers and the load oil pressure detection passage are communicated or blocked. It is characterized by becoming.

  According to this invention, the hydraulic check valve is fitted to the inner peripheral surface of the sleeve fixed to the housing so that the piston that moves due to the pressure difference of the hydraulic cylinder can be slid back and forth. Two oil chambers respectively connected to one oil passage through an on-off valve are defined, and two small holes respectively connecting the two oil chambers and a load oil pressure detection passage are formed in the sleeve, Since the two small holes are opened and closed by the movement of the piston in accordance with the difference in load hydraulic pressure between the two hydraulic oil chambers of the cylinder, and the two oil chambers and the load hydraulic pressure detection passage are communicated or blocked, the piston The two hydraulic oil chambers of the hydraulic cylinder are released by releasing the pressure of the oil chamber on the other side when one side of the two oil chambers is boosted by opening and closing the two small holes accompanying the movement of The change in the load hydraulic pressure can be compensated only by opening and closing the two small holes drilled in the sleeve by the movement of the piston, and the operating hydraulic pressure supplied to the hydraulic cylinder can always be kept higher than the required operating hydraulic pressure. .

  Therefore, according to this invention, the change of the load hydraulic pressure of the two hydraulic oil chambers of the hydraulic cylinder is perforated in the sleeve by the movement of the piston fitted to the inner peripheral surface of the sleeve fixed to the housing so as to be reciprocally slidable. It is possible to compensate by simply opening and closing the two small holes, eliminating the need for a shuttle valve built into the housing as in the prior art, and making the structure simpler and smaller than the prior art. Thus, the assembly man-hours and the number of parts are reduced, and a low-cost hydraulic check valve can be obtained.

  Further, in the hydraulic control device according to the present invention, the hydraulic check valve is defined by a piston that is fitted in a housing so as to be slidable in a reciprocating manner and moves by a pressure difference between two hydraulic oil chambers of the hydraulic cylinder. Two oil chambers connected to one oil passage through open / close valves respectively, and two land surfaces respectively facing the two oil chambers are formed on the piston, and two hydraulic oil chambers of the hydraulic cylinder are formed. The two land surfaces are configured to communicate or block the two oil chambers and the load oil pressure detection passage by the movement of the piston accompanying the difference in load oil pressure.

According to this invention, the change of the load hydraulic pressure of the two hydraulic oil chambers of the hydraulic cylinder is formed in the piston by the movement of the piston fitted to the inner peripheral surface of the housing of the hydraulic check valve so as to be slidable back and forth. In addition, it is possible to compensate by merely connecting or shutting off the two oil chambers and the load hydraulic pressure detection passage on the two land surfaces, and a shuttle valve built into the housing as in the prior art becomes unnecessary, Compared with such a conventional technique, the structure is simple and small, the number of assembly steps and the number of parts are reduced, and a low-cost hydraulic check valve can be obtained.
Further, since the two oil chambers and the load oil pressure detection passage are communicated or blocked by the two land surfaces formed on the piston, the sleeve having the two small holes as in the invention is not necessary. However, the structure is simple and small, and the number of assembly steps and the number of parts are reduced.

In the above invention, preferably, the piston connects the two oil chambers and the hydraulic pressure adjusting means, and has a small hole formed in the piston or a groove formed in a fitting surface on the outer periphery of the piston. The orifice part which consists of one or both is provided.
If comprised in this way, the buffering effect | action of the flow of the hydraulic fluid between two oil chambers and a load hydraulic pressure detection channel | path can be made | formed by the throttle effect of the orifice part formed in the piston, and detection load hydraulic pressure Abrupt changes in hydraulic pressure can be avoided, and the hydraulic check valve can be operated stably.

According to the present invention, one side of the two oil chambers defined by the piston is opened and closed by the opening and closing of the two small holes drilled in the sleeve accompanying the movement of the piston fitted to the sleeve so as to be reciprocally slidable. By releasing the pressure in the other oil chamber when the pressure is increased, the change in the load hydraulic pressure in the two hydraulic oil chambers of the hydraulic cylinder is compensated only by opening and closing the two small holes drilled in the sleeve by the movement of the piston. Therefore, the hydraulic pressure supplied to the hydraulic cylinder can always be kept higher than the required hydraulic pressure.
Therefore, according to the present invention, it is possible to compensate for changes in the load hydraulic pressure of the two hydraulic oil chambers of the hydraulic cylinder by simply opening and closing the two small holes drilled in the sleeve by the movement of the piston. This eliminates the need for a shuttle valve built into the housing as in the prior art, which makes the structure simpler and smaller than that of the prior art, reduces the number of assembly steps and parts, and provides a low-cost hydraulic check valve. It is done.

  According to another configuration of the present invention, a change in the load hydraulic pressure of the two hydraulic oil chambers of the hydraulic cylinder is caused by the movement of the piston so that the two oil chambers and the load hydraulic pressure are changed on the two land surfaces formed on the piston. It can be compensated only by communicating with or shutting off the detection passage, so that a shuttle valve built in the housing is unnecessary as described above, and the structure is simpler and smaller than the conventional technology, The assembly man-hours and the number of parts are reduced, and the cost is reduced. Furthermore, the two oil chambers and the load oil pressure detection passage are communicated or blocked by the two land surfaces formed in the piston. A sleeve having a small hole is not required, the structure is simple and small, and the number of assembly steps and the number of parts are reduced.

  Hereinafter, the present invention will be described in detail with reference to the embodiments shown in the drawings. However, the dimensions, materials, shapes, relative arrangements, and the like of the component parts described in this example are not intended to limit the scope of the present invention only to specific examples unless otherwise specified. Only.

FIG. 1 is a hydraulic system diagram including a cross-sectional view of a hydraulic check valve in a hydraulic control device for a hydraulic load handling work device for a forklift according to a first embodiment of the present invention, and FIG. 2 is an enlarged cross-sectional view of a portion Z in FIG.
1 and 2, reference numeral 103 denotes a hydraulic cylinder for driving a cargo handling work device of a forklift. The hydraulic cylinder 103 includes two hydraulic oil chambers 103a and 103b, and the cargo handling work device is connected to an output end thereof.
104 is a hydraulic pump driven by an engine (not shown), 100 is a hydraulic check valve to be described in detail later, 105 is a pressure control valve, 107 is a pressure regulating valve that regulates the maximum hydraulic pressure of the hydraulic operation system, and 106 is an oil tank.
The pressure control valve 105 controls the hydraulic pressure supplied to the hydraulic cylinder 103 to be always higher than the necessary hydraulic pressure based on the detected load hydraulic pressure from the hydraulic check valve 100.

A control valve 101 is driven by solenoids 101a and 101b, and supplies and discharges hydraulic fluid to the hydraulic cylinder 103, and controls the position. Two hydraulic fluid passages 124 and 125 from the control valve 101 are It is connected to the two hydraulic oil chambers 103 a and 103 b of the hydraulic cylinder 103 through the hydraulic check valve 100.
Further, the supply side port and the oil discharge side port of the control valve 101 are connected to the oil supply passage 112 from the pressure control valve 105 and the oil discharge passage 111 to the oil tank 106, respectively.
A load hydraulic pressure detection circuit 13 connects a load detection port 12 of the hydraulic pressure check valve 100, which will be described later, and the pressure control valve 105, and the load hydraulic pressure detected by the hydraulic pressure check valve 100 is connected to the load hydraulic pressure detection circuit. 13 is sent to the pressure control valve 105.
Reference numeral 108 denotes a check valve provided for each hydraulic pressure check valve 100 in the load hydraulic pressure detection circuit 13 for a plurality of hydraulic pressure check valves 100.

A hydraulic check valve 100 is configured as follows.
1 is a housing, 9a and 9b are outlet oil passages formed in the housing 1, 10a and 10b are outlet ports communicating with the outlet oil passages 9a and 9b, and the outlet port 10a (port A) is Connected to the hydraulic oil chamber 103 a of the hydraulic cylinder 103, the outlet port 10 b (port B) is connected to the hydraulic oil chamber 103 b of the hydraulic cylinder 103. 11a (port A) and 11b (port B) are inlet oil passages connected to the hydraulic oil passages 124 and 125 from the control valve 101, respectively.

Reference numeral 3 denotes a cylindrical sleeve fixed to the inner peripheral surface of the housing 1, and 4 denotes a piston fitted in the sleeve 3 so as to be slidable back and forth.
As shown in detail in FIG. 2, the piston 4 includes a land portion 44 that opens and closes small holes 31 a and 31 b of a sleeve 3, which will be described later, in the center portion, and a pair of left and right land portions 45 a and 45 b on both sides of the land portion 44. Further, push rod portions 47a and 47b are formed outside the left and right land portions 45a and 45b, and the outer peripheral surfaces of the land portions 44 and 45a and 45b are fitted to the inner peripheral surface of the sleeve 3. Are combined.

Two oil chambers 7a and 7b are defined on both sides of the piston 4 by left and right land portions 45a and 45b of the piston 4, and the two oil chambers 7a and 7b are formed in valve cases 2a and 2b described later. It is connected to the inlet oil passages 11a and 11b through the perforated passage holes 8a and 8b.
2a and 2b are valve cases fixed in the housing 1, and 6a and 6b are slidably fitted in the valve cases 2a and 2b so that the oil chambers 7a and 7b and the outlet oil passages 9a and 9b Open / close valve (20a, 20b is a seat part). 5a and 5b are springs for returning the on-off valves 6a and 6b, and 20a and 20b are spring receivers.

In FIG. 2, orifice holes 42 a and 42 b communicating the oil chambers 7 a and 7 b and the oil chambers 46 a and 46 b on both sides of the land portion 44 are formed in the left and right land portions 45 a and 45 b of the piston 4. Yes.
The sleeve 3 has two small holes 31 a and 31 b that penetrate through the inner and outer peripheries and are open to the load detection port 12. The length S2 between the outer end portions of the small holes 31a and 31b is formed to be a minute amount smaller than the width S1 of the land portion 44 to form a minute overlap when the piston 4 is moved.

In the hydraulic control apparatus having such a configuration, the hydraulic oil discharged from the hydraulic pump 104 and adjusted to a predetermined hydraulic pressure by the pressure control valve 105 enters the control valve 101 through the supply oil passage 112, and the control valve 101 Is switched to the A port side, for example, it enters the inlet oil passage 11a (port A) of the hydraulic check valve 100 through the hydraulic oil passage 124.
Then, the hydraulic oil enters the oil chamber 7a on the right side of FIG. 1 through the passage hole 8a, opens the on-off valve 6a to open, and operates the hydraulic cylinder 103 through the outlet oil passage 9a and the outlet port A10a. Entering the oil chamber 103a, the piston 103c of the hydraulic cylinder 103 is moved to the left in FIG.

On the other hand, the hydraulic pressure in the oil chamber 7a acts on the piston 4 to move the piston 4 to the left in FIG. By such movement of the piston 4, as shown in FIG. 2, the land surface 43 a of the land portion 44 moves to the position 43 b of the two-dot chain line to open the small hole 31 a of the sleeve 3. With the opening of the small hole 31a, the hydraulic oil in the oil chamber 7a enters the small hole 31a through the orifice hole 42a and the oil chamber 46a, and is sent to the load detection port 12 from the small hole 31a.
On the other hand, when the piston 4 moves to the left, the piston 4 pushes and opens the on-off valve 6b, and the hydraulic oil on the hydraulic oil chamber 103b side of the hydraulic cylinder 103 passes through the passage hole from the on-off valve 6b. 8b → Inlet oil passage 11b (Port B) → Control valve 101 → Oil drainage passage 111 The flow then returns to the oil tank 106.
At the same time, the hydraulic oil in the oil chamber 46b also flows through the orifice hole 42b as shown by an arrow B in FIG. 2, and operates from the hydraulic oil chamber 103b in the inlet oil passage 11b (port B). Merge with oil.

  As described above, since the orifice holes 42a and 42b are provided in the left and right land portions 45a and 45b of the piston 4, the two oil chambers 7a and 7b and the load oil pressure detection circuit are formed by the throttling effect of the orifice holes 42a and 42b. Therefore, the hydraulic pressure check valve 100 can be stably operated.

Then, the detected load hydraulic pressure of the hydraulic oil from the load detection port 12 is sent to the pressure control valve 105 through the load hydraulic pressure detection circuit 13 as shown in FIG. In the pressure control valve 105, based on the detected load oil pressure, the supply oil pressure of the hydraulic oil from the hydraulic pump 104 is set to a certain amount higher than the detected load oil pressure, and the control valve is passed through the supply oil passage 112. 101.
As a result, the hydraulic pressure of the hydraulic fluid supplied from the control valve 101 to the hydraulic cylinder 103 through the hydraulic check valve 100 is held at the supplied hydraulic pressure.
Even when the control valve 101 is switched to the B port side, the operation similar to the above is performed on the B port side.

  According to the first embodiment, the hydraulic check valve 100 is fitted to the inner peripheral surface of the sleeve 3 fixed to the housing 1 so that the piston 4 that moves due to the pressure difference of the hydraulic cylinder 103 is slidable. Two oil chambers 7a and 7b connected to the two oil passages 9a and 9b to the hydraulic cylinder 103 by the piston 4 via the on-off valves 6a and 6b are defined, and the two oil chambers 7a are formed in the sleeve 3. , 7b and the load hydraulic pressure detection circuit 13 are drilled in two small holes 31a, 31b, respectively, and the piston 4 moves due to the difference in load hydraulic pressure between the two hydraulic oil chambers 103a, 103b of the hydraulic cylinder 103. Since the two small holes 31a, 31b are opened and closed, and the two oil chambers 7a, 7b and the load oil pressure detection circuit 13 are communicated or blocked, the piston 4 When one side of the two oil chambers 7a and 7b is boosted by opening and closing the two small holes 31a and 31b accompanying the movement, the pressure of the oil chamber on the other side is released, whereby two hydraulic oils of the hydraulic cylinder 103 are released. The change in the load hydraulic pressure in the chambers 103a and 103b can be compensated by only opening and closing the two small holes 31a and 31b drilled in the sleeve 3 by the movement of the piston 4, and the operating hydraulic pressure supplied to the hydraulic cylinder 103 can be compensated. It can always be kept above the required hydraulic pressure.

  Therefore, according to the first embodiment, a change in the load hydraulic pressure of the two hydraulic oil chambers 103a and 103b of the hydraulic cylinder 103 is fitted to the inner peripheral surface of the sleeve 3 fixed to the housing 1 so as to be reciprocally slidable. The movement of the piston 4 makes it possible to compensate only by opening and closing the two small holes 31a and 31b drilled in the sleeve 3, and the shuttle valve 120 incorporated in the housing 1 as in the prior art. (Refer to FIG. 5) is not required, and the structure is simpler and smaller than the prior art, and the number of assembly steps and the number of parts are reduced, so that a low-cost hydraulic check valve 100 can be obtained.

FIG. 3 is a cross-sectional view of a main part of a hydraulic check valve in a hydraulic control device for a hydraulic cargo handling work device for a forklift according to a second embodiment of the present invention.
In this embodiment, two land surfaces 43a and 43b facing the two oil chambers 7a and 7b are formed in the land portion 44 on the center side of the piston 4, and the length between the land surfaces 43a to 43b is formed. That is, the width S1 of the land portion 44 is formed to be slightly larger than the width S3 of the annular groove 12s communicating with the load detection port 12 and overlapped.

With this configuration, for example, when the hydraulic pressure in the oil chamber 7a acts on the piston 4 and moves the piston 4 to the left in FIG. 3, the movement of the piston 4 causes the land surface 43a to move. Opens the annular groove 12s, and the hydraulic oil in the oil chamber 7a is sent to the load detection port 12 from the annular groove 12s through the orifice hole 42a and the oil chamber 46a. At this time, the working oil in the oil chamber 46b on the opposite side merges with the working oil from the working oil chamber 103b in the inlet oil passage 11b through the orifice hole 42b, the oil chamber 7b, and the passage hole 8b.
Even when the control valve 101 is switched to the B port side, the same operation as described above is performed on the B port side.

According to the second embodiment, pistons fitted to the inner peripheral surface of the housing 1 of the hydraulic check valve 100 so as to reciprocate are slidable with changes in the load hydraulic pressure of the two hydraulic oil chambers 103a and 103b of the hydraulic cylinder 103. By the movement of 4, the two land surfaces 43a and 43b formed on the piston 4 can be compensated only by connecting or blocking the two oil chambers 7a and 7b and the load oil pressure detection circuit 13. Thus, the shuttle valve 120 incorporated in the housing as in the prior art becomes unnecessary, and the structure is simpler and smaller than the prior art, and the number of assembly steps and the number of parts are reduced. Is obtained.
Further, in particular, according to the second embodiment, the two oil chambers 7a, 7b and the load oil pressure detection circuit 13 are communicated or blocked by the two land surfaces 43a, 43b formed on the piston 4, so that the first The sleeve 3 having the two small holes 31a and 31b as in the first embodiment is not necessary, the structure is simpler and smaller than the first embodiment, and the number of assembly steps and the number of parts are also reduced.

  In the first and second embodiments, as shown in FIG. 4, the left and right land portions 45a, 45a, 42b are replaced with or in addition to the orifice holes 42a, 42b of the piston 4. Orifice grooves 50a and 50b may be formed on the outer peripheral surface of 45b.

  According to the present invention, the conventional shuttle valve can be omitted by improving the internal structure of the hydraulic check valve, and the structure equivalent to that of the conventional shuttle valve can be exhibited. Therefore, it is possible to provide a hydraulic control device including a low-cost hydraulic check valve.

1 is a hydraulic system diagram including a cross-sectional view of a hydraulic check valve in a hydraulic control device for a hydraulic cargo handling work device of a forklift according to a first embodiment of the present invention. It is the Z section expanded sectional view of FIG. FIG. 3 is a diagram corresponding to FIG. 2 according to a second embodiment of the present invention. It is a perspective view which shows the other example of the piston in the said 1st, 2nd Example. It is a figure which shows an example of the prior art of the hydraulic control apparatus for hydraulic load handling work apparatuses of the forklift provided with the hydraulic check valve.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Housing 2a, 2b Valve case 3 Sleeve 4 Piston 6a, 6b On-off valve 7a, 7b Oil chamber 12 Load detection port 13 Load oil pressure detection circuit 31a, 31b Small hole 42a, 42b Orifice hole 44, 45a, 45b Land part 46a, 46b Oil chamber 50a, 50b Orifice groove 100 Hydraulic check valve 101 Control valve 103 Hydraulic cylinder 103a, 103b Hydraulic oil chamber 104 Hydraulic pump 105 Pressure control valve 106 Oil tank

Claims (3)

  A hydraulic oil passage connecting a hydraulic cylinder and a control valve for supplying, discharging, and controlling the position of hydraulic oil to the hydraulic cylinder is connected to a hydraulic oil outlet of the control valve and two hydraulic oil chambers of the hydraulic cylinder. A hydraulic pressure check valve for opening and closing two oil passages and detecting a change in the load hydraulic pressure of the hydraulic cylinder, and the load hydraulic pressure detection value from the hydraulic pressure check valve is input to the pressure control valve, and the load hydraulic pressure is detected by the pressure control valve. In the hydraulic control apparatus configured to control the load hydraulic pressure to the target hydraulic pressure based on the detected value, the hydraulic check valve fixes a sleeve to the inner peripheral surface of the housing, and the hydraulic cylinder is fixed to the inner peripheral surface of the sleeve. A piston that moves due to a pressure difference between the two hydraulic oil chambers is fitted so as to be reciprocally slidable. The piston is partitioned by the piston and is connected to the two oil passages via an on-off valve. Two oil chambers connected to each other, and two small holes respectively connecting the two oil chambers and the load hydraulic pressure detection passage are formed in the sleeve, and the loads of the two hydraulic oil chambers of the hydraulic cylinder are formed. A hydraulic control device configured to open and close the two small holes by movement of the piston in accordance with a difference in hydraulic pressure, and to connect or block the two oil chambers and a load hydraulic pressure detection passage.   A hydraulic oil passage connecting a hydraulic cylinder and a control valve for supplying, discharging, and controlling the position of hydraulic oil to the hydraulic cylinder is connected to a hydraulic oil outlet of the control valve and two hydraulic oil chambers of the hydraulic cylinder. A hydraulic pressure check valve for opening and closing two oil passages and detecting a change in the load hydraulic pressure of the hydraulic cylinder, and the load hydraulic pressure detection value from the hydraulic pressure check valve is input to the pressure control valve, and the load hydraulic pressure is detected by the pressure control valve. In the hydraulic control apparatus configured to control the load hydraulic pressure to the target hydraulic pressure based on the detected value, the hydraulic check valve is fitted in a housing so as to be slidable back and forth, and the pressures of the two hydraulic oil chambers of the hydraulic cylinder The two oil chambers defined by the piston moving by the difference and connected to the two oil passages via the on-off valve are provided, and Two land surfaces respectively facing the two oil chambers are formed, and the two land surfaces are separated from the two oil chambers by the movement of the piston due to a difference in load oil pressure between the two hydraulic oil chambers of the hydraulic cylinder. A hydraulic control device configured to communicate with or shut off a hydraulic pressure detection passage. The piston connects the two oil chambers with the hydraulic pressure adjusting means, and is an orifice composed of one or both of a small hole drilled in the piston or a groove formed in a fitting surface of the outer periphery of the piston. The hydraulic control device according to claim 1, further comprising a portion.

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