JP3618530B2 - Directional control valve - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a directional control valve, and in particular, when a part of return oil from a hydraulic actuator is regenerated to the supply side, appropriate load control can be achieved without increasing the discharge flow rate of the hydraulic pump. It relates to a directional control valve.
[0002]
[Prior art]
As directional control valves equipped with a regeneration circuit for regenerating and using discharged oil, those described in, for example, Japanese Patent Publication No. 46-15059 (Hydreco type) and Japanese Patent Publication No. 41-10446 (Husco type) are known. .
[0003]
However, in recent years, the driving pressure of the hydraulic device has become very high, and the conventional hydration type directional control valve in the regeneration circuit is equipped with double and triple poppet valves inside the spool. Therefore, if sufficient internal passages are secured, there is anxiety about the spool strength, and if the emphasis is placed on strength, not only the internal passages can be secured, but also the processing shape inside the spool becomes complicated. Yes.
[0004]
Various other types are also known, but most of them use the inside of the spool and have the same difficulties as described above.
[0005]
Furthermore, in the Hasco type directional control valve, the above-mentioned problems are avoided, but when the spool is neutral, there is a load prevention valve for the actuator, and there is a reverse between the passage between the main tank and the load prevention valve. Since there is a stop valve, it has a disadvantage that does not work.
[0006]
On the other hand, in a conventional directional control valve having a drainage throttle function, for example, in the case where a throttle device with a check valve is provided outside the directional control valve, a required installation space is required, and a free flow is required. In order to secure the passage, the structure of the check valve becomes large, and the entire apparatus has a difficulty in increasing the size. In addition, a directional control valve with a metering notch formed in the spool and its opening area changed by the movement of the spool so as to restrict the drained oil can save space and cost. Although it has the advantage that it can be, the spool becomes dedicated by adjusting to the falling speed of the actuator used, and various types of spools must be manufactured due to the shape of the metering notch, etc. Has difficulties.
[0007]
From this point of view, the applicant of the present invention has a simple structure, can sufficiently maintain the spool strength when the regeneration circuit is formed, and impairs the function of the load prevention valve even when the spool is neutral. Regenerative circuit can be formed without any problems, and at the time of oil drainage throttling, it is possible to cope with only the necessary replacement of parts, and the internal structure has been simplified to develop a directional control valve that is easy to manufacture and adjust. A registration application was filed (Japanese Utility Model Laid-Open No. 6-25602, Utility Model Registration No. 2500378).
[0008]
Specifically, as shown in FIG. 2, the directional control valve according to the proposal includes a pair of supply / discharge oil passages 14 and 16 in the casing 10 and a supply oil passage provided inside the supply / discharge oil passages 14 and 16. 18, tank oil passages 20, 22 provided outside the supply / discharge oil passages 14, 16, and a spool 12 that opens and closes each oil passage, and the supply / discharge oil according to the movement of the spool 12. A directional control valve configured to supply and discharge fluid from supply / discharge oil ports 17 and 19 communicating with the passages 14 and 16, and supply / discharge oil passage communicated with one of the pair of supply / discharge oil ports 17 and 19 A sub tank chamber 28 is provided between the tank 16 and the tank oil passage 22, and a back pressure valve 32 is provided for a part of the sub tank chamber 28, so that the sub tank chamber 28 and the tank oil passage 22 communicate with each other. At the same time as a fluid communicating with the supply oil passage 18. And a check valve 38 provided at one end inside the Lumpur 12, which is constituted so as to communicate with the supply oil passage 18 and the sub tank chamber 28.
[0009]
In the directional control valve configured as described above, the dropping speed at the time of dropping the load by the spool 12 is determined by the weight of the load, and when the amount of oil on the pressure side of the hydraulic cylinder 50 is insufficient, the oil supply / discharge oil When the fluid discharged from the port 19 is introduced into the sub-tank chamber 28 and the pressure side of the hydraulic cylinder 50 becomes negative, the check valve 38 is opened to supply the supply oil passage 18 and the supply / discharge oil passage 14 from the sub-tank chamber 28. Insufficient fluid is replenished to the pressure side of the hydraulic cylinder 50. Further, when the supply oil is filled on the pressure side of the hydraulic cylinder 50 and the pressure in the supply oil passage 18 is increased from the set pressure of the back pressure valve 32, the check valve 30 is closed and the fluid in the sub tank chamber 28 is transferred to the back pressure valve. It is discharged to the tank oil passage 22 through 32. Thereby, the regeneration function and the oil drainage throttling function can be generated.
[0010]
[Problems to be solved by the invention]
However, the following problem to be solved remains in the directional control valve according to the proposal.
[0011]
That is, in FIG. 2, when the hydraulic cylinder 50 is, for example, a boom hydraulic cylinder of a hydraulic excavator, the spool 12 is moved to the left in the drawing to introduce pressure oil into the head side oil chamber 50b of the hydraulic cylinder 50. When the load W is increased and the hydraulic cylinder 50 is operated to the stroke end and the load W is decreased from this state, the drop speed is determined by the load W as described above. For this reason, it is meaningless to generate more pressure than necessary in the hydraulic pump 25.
[0012]
In order to avoid this problem, when the spool 12 is moved by a full stroke in the right direction in the drawing, a part of the pressure oil discharged from the hydraulic pump 25 is supplied to the negative variable discharge flow control pressure generator 40 (hereinafter, By passing through the bleed notch 39 to the bypass passages 21 and 26 communicating with the negative control pressure generator 40), a negative variable discharge flow rate control pressure (hereinafter abbreviated as negative control pressure) is generated. The discharge flow rate from the hydraulic pump 25 is set to be lowered.
[0013]
However, when the load W is lowered and the pressure on the rod side oil chamber 50a of the hydraulic cylinder 50 is required to lift the hydraulic excavator itself, the area of the bleed notch 39 is made too large. I can't. For this reason, it is difficult to sufficiently satisfy both the energy saving effect necessary for lowering the load W and the supply of pressure necessary for lifting the hydraulic excavator.
[0014]
Therefore, as a result of extensive research, the inventor has provided a pair of supply / discharge oil passages in the casing, a supply oil passage provided inside the supply / discharge oil passage, and an outside of the supply / discharge oil passage. A tank oil passage that is formed, and a spool that opens and closes each of the oil passages, and is configured to supply and discharge fluid from a supply and discharge oil port that communicates with the supply and discharge oil passage according to the movement of the spool, A sub tank chamber is provided between a supply / discharge oil passage communicating with one of the pair of supply / discharge oil ports and a tank oil passage, and a back pressure valve is provided for a part of the sub tank chamber, and the sub tank chamber and the tank oil are provided. A directional control valve configured to communicate with the supply oil path, and provided with a check valve inside one end of a spool communicating with the supply oil path, to communicate with the supply oil path and the sub tank chamber; The supply / discharge oil passage and the sub tank chamber are connected to each other. And providing an oil passage in the spool that communicates the sub tank chamber and the bypass passage with each other for guiding a part of the fluid in the sub tank chamber to the negative control pressure generator through the bypass passage. When the load is controlled by the hydraulic cylinder by moving the spool, the check valve provided inside one end of the spool is opened when the oil volume in one oil chamber of the hydraulic cylinder is insufficient and the pressure is negative. In addition, the oil chamber can be replenished with insufficient fluid by communicating the subtank chamber with the oil passage in the spool via the oil passage in the spool. In this case, when the set pressure of the back pressure valve is set slightly lower than the set pressure of the negative pressure generator, the pressure in the supply oil passage becomes higher than the set pressure of the back pressure valve. The check valve provided in the tank is closed, the fluid in the sub tank chamber is discharged to the tank oil passage through the back pressure valve, and a part of the fluid in the sub tank chamber is introduced into the negative control pressure generator through the oil passage in the spool. It was found that proper load control by the hydraulic cylinder can be achieved without increasing the discharge flow rate of the hydraulic pump.
[0015]
Accordingly, an object of the present invention is to provide a directional control valve capable of achieving proper load control without increasing the discharge flow rate of the hydraulic pump when a part of the return oil from the hydraulic actuator is regenerated to the supply side. Is to provide.
[0016]
[Means for Solving the Problems]
In order to achieve the above object, a directional control valve according to the present invention includes a pair of supply / discharge oil passages in a casing, a supply oil passage provided inside the supply / discharge oil passage, and an outside of the supply / discharge oil passage. A tank oil passage provided in the tank and a spool that opens and closes each of the oil passages, and is configured to supply / discharge fluid from a supply / discharge oil port communicating with the supply / discharge oil passage according to the movement of the spool. A sub-tank chamber is provided between a supply / discharge oil passage communicating with one of the pair of supply / discharge oil ports and a tank oil passage, and a back pressure valve is provided for a part of the sub-tank chamber, A direction configured to communicate with the tank oil passage, and to provide a check valve in one end of a spool communicating with the supply oil passage so that the supply oil passage and the sub tank chamber communicate with each other. In the control valve,
An oil passage in the spool that connects the supply / discharge oil passage and the sub tank chamber to each other, and the sub tank chamber and the bypass passage for guiding a part of the fluid in the sub tank chamber to the negative control pressure generator through the bypass passage, And an oil passage in the spool that communicates with each other.
[0017]
In this case, when the load is controlled by the hydraulic cylinder by operating the spool, if the oil amount in one oil chamber of the hydraulic cylinder becomes negative and the negative pressure is reached, a check valve provided inside one end of the spool is provided. The oil tank can be configured to open and communicate with the oil supply / discharge oil passage through the sub tank chamber and the oil passage in the spool to replenish the oil chamber with the insufficient fluid.
[0018]
In addition, when the set pressure of the back pressure valve is set slightly lower than the set pressure of the negative control pressure generator, and the pressure of the supply oil passage becomes higher than the set pressure of the back pressure valve, a check valve provided inside one end of the spool is provided. By closing, discharging the fluid in the sub tank chamber to the tank oil passage through the back pressure valve, and by introducing a part of the fluid in the sub tank chamber to the negative control pressure generator via the oil passage in the spool, The load control by the hydraulic cylinder can be achieved without increasing the discharge flow rate of the hydraulic pump.
[0019]
【Example】
Next, embodiments of a directional control valve according to the present invention will be described in detail below with reference to the accompanying drawings. For convenience of explanation, the same components as those of the conventional structure shown in FIG.
[0020]
FIG. 1 is a schematic sectional view showing an embodiment of a directional control valve according to the present invention. That is, in FIG. 1, reference numeral 10 indicates a casing, and a spool 12 is slidably inserted into the casing 10, and a pair of supply / discharge oil passages 14, 16 and the supply / discharge oil passages 14, 16 are provided. Connected supply / discharge oil ports 17, 19, an inverted U-shaped supply oil passage 18 disposed inside the supply / discharge oil passages 14, 16, and a tank oil passage 20 connected to the tank 23 outside thereof. , 22 are arranged respectively.
[0021]
A bypass passage 24 communicating with the hydraulic pump 25 is provided at the center of the supply oil passage 18, and the bypass passage 24 and the supply oil passage 18 are connected via a check valve 27. A pair of bypass passages 21 and 26 communicating with the tank 23 are disposed between the supply oil passage 18 and the bypass passage 24.
[0022]
In the directional control valve configured as described above, the pressure oil from the hydraulic pump 25 is supplied from the bypass passage 24 to the supply oil passage 18 via the check valve 27, and when the spool 12 is neutral, the bypass passage 21 or It operates so as to flow 26 and return to the tank 23.
[0023]
A sub tank chamber 28 is provided between one of the pair of supply / discharge oil ports 17, 19 and the tank oil passage 22, and the sub tank chamber 28 and the supply oil passage 18 are provided with a spool. 12 is connected through a check valve 38 incorporated in the inside. The sub tank chamber 28 is also connected to the tank oil passage 22 via a back pressure valve 32.
[0024]
Reference numerals 34 and 36 are known actuator protection function members in which an overload relief valve and a negative pressure prevention valve are integrated, and are arranged between the supply / discharge oil passages 14 and 16 and the tank oil passage 22. It is installed. The pair of supply / discharge oil ports 17 and 19 are respectively connected to the hydraulic cylinder 50, and the load W can be moved up and down by supplying pressure oil to the hydraulic cylinder 50.
[0025]
In the directional control valve of this embodiment, a pair of bypass passages 21 and 26 communicating with the tank 23 are arranged between the supply oil passage 18 and the bypass passage 24 via the negative control pressure generator 40, respectively. It is installed.
[0026]
However, in the directional control valve according to this embodiment having the above-described configuration, when the load W is lowered by moving the spool 12 in the right direction, the drop speed is determined by the weight of the load W.
[0027]
However, for example, even when the total amount of oil discharged from the hydraulic pump 25 is fed, the amount of oil in the rod side oil chamber 50a of the hydraulic cylinder 50 may be insufficient.
[0028]
Therefore, in the present invention, the spool 12 is provided with oil passages 42a, 42b, and 42c that allow the supply / discharge oil passage 14 and the sub tank chamber 28 to communicate with each other, and a part of the fluid in the sub tank chamber 28 is bypassed. Oil passages 42 a, 42 b, 42 d are provided to lead the sub tank chamber 28 and the bypass passage 21 to each other to lead to the negative control pressure generator 40 through the passage 21.
[0029]
With this configuration, when the rod-side oil chamber 50a of the hydraulic cylinder 50 becomes negative pressure, the check valve 38 is opened, and the oil passages 42a, 42b, 42c provided in the spool 12 from the sub tank chamber 28. In addition, the insufficient fluid is replenished to the rod-side oil chamber 50 a of the hydraulic cylinder 50 through the supply / discharge oil passage 14. When the supply oil is filled in the rod side oil chamber 50a of the hydraulic cylinder 50 and the pressure in the supply oil passage 18 becomes higher than the set pressure of the back pressure valve 32, the check valve 38 is closed and the fluid in the sub tank chamber 28 is discharged. The oil is discharged to the tank oil passage 22 through the back pressure valve 32.
[0030]
At this time, by setting the set pressure of the back pressure valve 32 to be slightly lower than the set pressure of the negative control pressure generating device 40, oil passages 42a, 42b provided in the spool 12 with a part of the fluid in the sub tank chamber 28. , 42 d and the bypass passage 21, leading to the negative control pressure generator 40, and appropriate load control by the hydraulic cylinder 50 can be achieved without increasing the discharge flow rate of the hydraulic pump 25.
[0031]
At this time, even if a pressure sufficient to lift the hydraulic excavator itself is required in the rod-side oil chamber 50a of the hydraulic cylinder 50, a part of the discharge flow rate from the hydraulic pump 25 needs to be guided to the negative control pressure generator 40. Therefore, it is possible to ensure a sufficient pressure.
[0032]
The preferred embodiments of the present invention have been described above, but the present invention is not limited to the above-described embodiments, and many design changes can be made without departing from the spirit of the present invention.
[0033]
【The invention's effect】
As described above, the directional control valve according to the present invention includes a pair of supply / discharge oil passages in the casing, a supply oil passage provided inside the supply / discharge oil passage, and an outside of the supply / discharge oil passage. A tank oil passage provided and a spool that opens and closes each of the oil passages, and is configured to supply and discharge fluid from a supply / discharge oil port communicating with the supply / discharge oil passage according to the movement of the spool, A sub tank chamber is provided between a supply / discharge oil passage communicating with one of the pair of supply / discharge oil ports and a tank oil passage, and a back pressure valve is provided for a part of the sub tank chamber, and the sub tank chamber and the tank are provided. A directional control configured to communicate with the oil passage, and provided with a check valve inside one end of a spool communicating with the supply oil passage so that the supply oil passage and the sub tank chamber communicate with each other. In the valve, the supply / discharge oil passage and the sub tank chamber are connected to each other. An oil passage in the spool that communicates with each other, and an oil passage in the spool that communicates the sub tank chamber and the bypass passage with each other for guiding a part of the fluid in the sub tank chamber to the negative pressure generator through the bypass passage. With this configuration, when the load is controlled by the hydraulic cylinder by moving the spool and the oil amount in one oil chamber of the hydraulic cylinder is insufficient and the negative pressure is reached, the oil is supplied from the sub tank chamber. The hydraulic cylinder can be replenished with insufficient fluid in the chamber, and part of the fluid in the sub tank chamber can be introduced into the negative control pressure generator via the oil passage in the spool, without increasing the discharge flow rate of the hydraulic pump. Appropriate load control can be achieved.
[Brief description of the drawings]
FIG. 1 is a schematic sectional view showing an embodiment of a directional control valve according to the present invention.
FIG. 2 is a schematic cross-sectional view showing a configuration of a conventional directional control valve.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 Casing 12 Spool 14, 16 Supply / discharge oil path 17, 19 Supply / discharge oil port 18 Supply oil path 20, 22 Tank oil path 21, 26 Bypass path 23 Tank 24 Bypass path 25 Hydraulic pump 27 Check valve 28 Sub tank chamber 32 Back pressure valve 34, 36 Actuator protection function member (load prevention valve)
38 Check valve 40 Negative control pressure generators 42a, 42b, 42c, 42d Spool oil passage 50 Hydraulic cylinder 50a Rod side oil chamber 50b Head side oil chamber

Claims (3)

A pair of supply / discharge oil passages in the casing, a supply oil passage provided inside the supply / discharge oil passage, a tank oil passage provided outside the supply / discharge oil passage, and the oil passages are opened and closed. A supply and discharge oil that is configured to supply and discharge fluid from a supply and discharge oil port that communicates with the supply and discharge oil passage according to the movement of the spool, and that communicates with one of the pair of supply and discharge oil ports. A sub tank chamber is provided between the passage and the tank oil passage, a back pressure valve is provided for a part of the sub tank chamber, and the sub tank chamber and the tank oil passage are communicated with each other. In the direction control valve configured to provide a check valve inside one end of the spool communicating with the path, and to communicate the supply oil path and the sub tank chamber,
An oil passage in the spool that connects the supply / discharge oil passage and the sub tank chamber to each other, and the sub tank chamber and the bypass passage for guiding a part of the fluid in the sub tank chamber to the negative control pressure generator through the bypass passage, A directional control valve characterized by providing an oil passage in the spool that communicates with each other. When moving the spool and performing load control with the hydraulic cylinder, if the oil volume in one oil chamber of the hydraulic cylinder is insufficient and negative pressure is generated, the check valve provided inside one end of the spool is opened and the sub tank 2. A directional control valve according to claim 1, wherein the oil chamber is connected to a supply / discharge oil passage through an oil passage in the spool so that the oil chamber is replenished with insufficient fluid. When the set pressure of the back pressure valve is set slightly lower than the set pressure of the negative control pressure generator, and the pressure of the supply oil passage becomes higher than the set pressure of the back pressure valve, the check valve provided inside one end of the spool is closed, 2. The structure according to claim 1, wherein the fluid in the sub tank chamber is discharged to the tank oil passage through the back pressure valve, and a part of the fluid in the sub tank chamber is introduced into the negative control pressure generator through the oil passage in the spool. Directional control valve.

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