JP4791823B2 - Hydraulic control valve used in load sensing type hydraulic control device - Google Patents

Description

  The present invention relates to a multiple-type hydraulic control valve in a flow rate control system employing a load sensing function, which is used in a hydraulically operated construction machine, and particularly used in a load sensing system hydraulic control apparatus having a hunting suppression function. The present invention relates to a hydraulic control valve.

  A flow rate control method called load sensing detects the maximum load pressure of multiple actuators in a hydraulic control device that controls multiple actuators with a single pump so that the discharge pressure of the pump becomes a constant higher pressure than the detected pressure. This is a control method. This difference in load pressure with respect to the pump pressure is usually called load sensing differential pressure. When multiple actuators are operated, the pump discharge pressure is controlled to a pressure higher than the maximum load pressure of the multiple actuators. In recent years, it has been attracting attention as an energy saving control method by supplying only oil.

  FIG. 3 shows a typical structure of a hydraulic control valve for a construction machine using such a load sensing function (Patent Document 1).

  FIG. 3 shows a conventional example of a hydraulic control valve constituting a hydraulic control apparatus having a load sensing function. That is, in FIG. 3, reference numeral 30 indicates a valve body. The valve body 30 has a common pressure oil supply passage 32 that receives supply of pressure oil from the variable displacement pump P, a switching spool 34, and this switching spool. An intermediate chamber 36 that receives supply of pressure oil from the pressure oil supply passage 32 by the movement of 34, cylinder ports 38a and 38b, passages 40 and 40 from the intermediate chamber 36 to the cylinder port 38a or 38b, and a check valve. 42, and auxiliary ports 44 and 44 for discharging the pressure oil in the cylinder port 38a or 38b to the tank T by the movement of the switching spool 34, and a tank line 47, respectively.

  The switching spool 34 is provided with a notch 33 for connecting the pressure oil supply passage 32 to the intermediate chamber 36 as the switching spool 34 moves. The switching spool 34 is provided with notches 45, 45 'and 46, 46' for connecting the cylinder port 38a or 38b to the passage 40 or the auxiliary port 44 as the switching spool 34 moves. Yes.

  The auxiliary ports 44 and 44 are provided between the cylinder ports 38 a and 38 b and the tank line 47, and between the auxiliary ports 44 and 44 and the tank line 47, the cylinder ports 38 a and 38 b are connected to the tank line 47. A flow rate adjusting means 48 for adjusting the opening degree A of the passage is provided.

  The flow rate adjusting means 48 includes a spool 50 and a spring 52. The spool 50 is slidably and liquid-tightly held in spool holes 53, 54 and 55 formed in the valve body 30, respectively. One end is surrounded and held by the cover 56. One end of the internal passage 58 provided in the spool 50 is connected to the back chamber 62 formed in the cover 56 through the check valve 60 and the passage 61, and the other end opens to the front chamber 64. In this case, the check valve 60 is incorporated so as to prevent the flow of pressure oil from the back chamber 62 to the front chamber 64.

  On the other hand, the front chamber 64 is connected to the intermediate chamber 36 through a passage 65, and the spring 52 is housed and disposed in the front chamber 64 to elastically hold the other end of the spool 50. Yes.

  In this way, the flow rate adjusting means 48 has its opening degree A while the shoulder 50a of the spool 50 is engaged with the spool hole 54 as the spool 50 moves downward against the elasticity of the spring 51. Is configured to be gradually reduced by being restricted by the notch 50b.

  In FIG. 3, the center bypass passage 66 is provided for the switching spool and configured as an open center type hydraulic control device. However, it is of course possible to configure as a closed center type hydraulic control device. is there.

  In addition, the actual construction machine includes a plurality of switching valves having the configuration shown in FIG. 3, and the back valve 62 of the switching valve shown in FIG. The back chambers (for example, 62 a, 62 b, 62 c) are connected to each other via a communication path 68, and the communication path 68 is connected to the tank T through an appropriate throttle 70.

(1) When the switching valve of FIG. 3 is operated alone In other words, in the hydraulic control device having the spool shown in FIG. 3 or a plurality of switching valve spools having the same configuration, any one of the switching spools is operated. In this case, for example, in FIG. 3, when the switching spool 34 is moved to the right, a notch 33 provided in a part of the switching spool 34 opens into the common pressure oil supply passage 32, and the pressure oil is discharged from the opening. Flows into the intermediate chamber 36, the pressure oil opens the check valve 42, reaches the one cylinder port 38b through the passage 40 and the notch 45 'provided in the switching spool 34, and is supplied to an actuator (not shown). The

  On the other hand, return oil from an actuator (not shown) flows in from the other cylinder port 38 a, reaches the auxiliary port 44 through the notch 46 provided in the switching spool 34, and the recess 51 of the spool 50 of the flow rate adjusting means 48. It passes through an annular passage 54 a formed by a spool hole 54 provided in the valve body 30, reaches the tank line 47, and is discharged to the tank T.

  Therefore, in the case of single operation, in the flow rate adjusting means 48, the pressure oil in the intermediate chamber 36 reaches the back chamber 62 through the passage 65, the front chamber 64, the internal passage 58 of the spool 50, the check valve 60, and the passage 61. . Further, this pressure oil communicates with the back chambers (62a, 62b, 62c) related to the other switching valves via the communication path 68, and a part thereof is discharged to the tank T through the relatively small throttle 70. Therefore, the pressure in the back chamber 62 is almost the same as that in the front chamber 64. Moreover, in this case, the spool 50 holds the opening A of the annular passage 54a in the open position by the spring force of the spring 52 provided in the front chamber 64, so that the return oil from the cylinder port 38a is adjusted in flow rate. Without being restricted by the means 48, it can be discharged to the tank T.

On the other hand, (2) When switching spools of a plurality of switching valves are operated simultaneously (operation on the high load side)
The spool 50 on the high load side is the same as that in the single operation. When the switching spools of a plurality of switching valves are operated simultaneously (operation on the light load side), if the switching valve shown in FIG. 3 is on the light load side, the switching spool 34 is moved to the right as in the case of the single operation. When operated in the same direction, the flow direction of the pressure oil becomes the same as in the case (1), but the flow rate adjusting means 48 has a high load on the back chamber 62 as in the case (1). The pressure in the intermediate chamber (36) on the side flows in through the communication passage 68, and this pressure oil is supplied to the front chamber 64 on the light load side by a check valve 60 provided in the spool 50 on the light load side. Therefore, the pressure in the back chamber 62 on the light load side is higher than the pressure in the front chamber 64 on the light load side. Accordingly, when the force due to the pressure difference of the back chamber 62 with respect to the front chamber 64 overcomes the spring force of the spring 52, the spool 50 is moved downward.

  In this case, in the flow rate adjusting means 48, the annular passage 54 a is narrowed by the shoulder 50 a of the spool 50, so the opening degree A is limited. Accordingly, the return oil from the cylinder port 38a is subjected to resistance in the process of being discharged to the tank line 47. Further, the pressure oil is supplied to the actuator (not shown) that has received this resistance, that is, the pressure to the cylinder port 38b. The pressure also rises on the oil supply side.

  As a result, if the pressure in the front chamber 64 of the light load side flow rate adjusting means 48 is increased and the spring force of the spring 52 is set to be relatively small, the spool 50 restricts the opening degree A while restricting the opening degree A. And the back chamber 62 are balanced at a position where the pressures are substantially equal. That is, the pressure in the front chamber 64 and the intermediate chamber 36 communicating with the front chamber 64 is substantially the same as the pressure in the intermediate chamber 36 on the high load side, so that the pressure oil from the pressure oil supply passage 32 is on the high load side and the light load. It can supply to both sides simultaneously and according to the opening degree of the notch 33 of each switching spool 34.

  In the prior art, the flow rate adjusting means for limiting the opening on the light load side when two or more switching valves are operated simultaneously is provided between the pressure oil supply passage and the cylinder port. However, in such a conventional technology, the following problems occur depending on the application. That is, when this is replaced with the switching spool shown in FIG. 3, when the switching valve is operated alone, the actuator connected to the switching valve is driven at a sufficient speed, so that the cylinder port is moved to the tank line. It is necessary to set the opening of the notch in the switching spool on the side from which the return oil is discharged to a necessary and sufficient size. However, in the light load side switching spool when two or more switching spools are operated at the same time, when the opening degree of the discharge side passage is increased as described above, the resistance of the passage is given to the supply side of the actuator. In the case of a load in which the external force acting on the actuator falls by its own weight, the resistance of the return oil discharge side passage is low, so it tries to fall at a high speed. Cavitation occurs, and there is a difficulty with great danger in the operation of the actuator. In order to avoid such a problem, the opening degree of the return oil discharge side passage may be reduced. However, in this case, there is a problem that the speed during the single operation is slowed as described above.

  However, in the hydraulic control apparatus having the switching valve shown in FIG. 3, in order to obtain a necessary and sufficient speed in a single operation, even if the opening degree of the switching spool in the return oil discharge side passage is set large, this Even when the switching valve corresponds to a switching valve on the light load side when two or more switching valves having different loads are operated at the same time, the opening of the passage on the discharge side is limited as described above. Even if the load is such that the external force acting on the actuator connected to the valve falls by its own weight, there is no danger of being inoperable and the safety is excellent. Therefore, a necessary and sufficient speed can be obtained in the single operation, and an operation with excellent safety can be performed in the simultaneous operation.

  In the hydraulic control apparatus having the switching valve shown in FIG. 3 described above, a spring 52 is provided in the front chamber 64 with respect to the spool 50 of the flow rate adjusting means 48, and the spool 50 is opened by this spring force. Although the held configuration is shown, the spring 52 can be provided on the back chamber 62 side. In this case, the auxiliary port 44 and the tank line 47 are shut off in a neutral state, so that the response at the time of starting Although there is a possibility of delay, it is possible to escape the load that falls by its own weight, and it is possible to obtain the same effect as in the configuration shown in FIG.

Japanese Patent No. 3264651 (FIG. 1)

  However, when the conventional load sensing control system disclosed in Patent Document 1 is adopted, it is possible to supply pressure oil regardless of the load pressure, but an actuator having a high load pressure, an actuator having a large inertia, or a load. When the pressure fluctuates, if the pressure higher than a certain load pressure is continuously supplied, the actuator vibrates (hunts), and the reaction causes the machine itself, and further, the operator vibrates with the aircraft, As a result, the operating lever is moved to amplify the vibration, and the operator feels uncomfortable due to the vibration.

  As a result of various studies and researches to solve the above-mentioned problems, the present inventor has found that the switch valve spool is moved into a hydraulic control valve hydraulically connected to the actuator while the switching valve spool moves by a predetermined amount from the neutral state. It has been found that the above problems can be basically solved by causing the pressure oil from the side to bleed off.

  Accordingly, an object of the present invention is to provide a hydraulic control device that employs a load sensing method, in which the actuator does not cause hunting, and further, even if a provisional command or actuator causes hunting, it can be quickly attenuated to achieve good results. An object of the present invention is to provide a hydraulic control valve that can be used in a load sensing type hydraulic control device that can obtain operability.

  In order to achieve the above object, a hydraulic control valve used in a load sensing type hydraulic control device according to the present invention receives a hydraulic oil from a pump and supplies / discharges the hydraulic oil to / from an actuator via a cylinder port. A through hole for a spool that is formed in the valve body of the hydraulic control valve and slidably accommodates the spool, and a pump port that has an opening that is formed in the valve body and opens into the through hole for the spool. An intermediate chamber formed in the valve body and having an opening that opens to the spool through-hole, and is formed in the valve body so as to be able to communicate with the intermediate chamber, and pressure oil in the intermediate chamber is supplied to the hydraulic control valve. A distribution passage for leading to the cylinder port and an opening formed in the valve body and opening to the through hole for the spool, and return oil from the cylinder port to the tank port A return passage leading to the tank, a tank port formed in the valve body in the vicinity of the intermediate chamber and having an opening opening to the through hole for the spool, and formed in the spool, when the spool is in a neutral position A first land for blocking between the pump port and the intermediate chamber; and the pump port and the intermediate chamber formed on the outer peripheral surface of the first land when the spool is moved from the neutral position by a first predetermined amount. A notch portion that communicates with each other, and when the spool is in a neutral position, the intermediate chamber and the tank port are in communication with each other, and at least the communication state is maintained when the spool has moved by the first predetermined amount. And a bleed-off passage formed in the spool.

  In this case, it is preferable that the tank port is formed at one place on the opposite side to the pump port with respect to the intermediate chamber.

  In this case, the bleed-off passage is between the second land formed on the intermediate chamber side and the third land formed on the tank port side when the spool is in the neutral position. It can comprise so that it may have the formed small diameter part.

  Furthermore, a cut portion can be formed on each of the outer peripheral surfaces of the second land and the third land.

  Furthermore, the distribution passage is formed and arranged on one side of the spool central shaft, and a check valve can be provided in the middle of the distribution passage.

  Further, in that case, the return passage can be formed and arranged on the other side of the spool central shaft.

  In this case, a common passage is formed in the valve body of the hydraulic control valve to guide the load pressure of the other hydraulic control valve constituting the hydraulic control device, and the common passage and the intermediate chamber are reversed. It can comprise so that it may connect through a stop valve.

  In that case, a pressure compensation valve can be formed and arranged on the connection passage connected through the check valve.

  The return passage may be provided with a check valve, and a passage for supplying return oil from the check valve to the distribution passage side may be formed in the valve body.

  According to the present invention, in the hydraulic control valve that receives the pressure oil from the pump and supplies / discharges the pressure oil to / from the actuator via the cylinder port, the hydraulic control valve is formed in the valve body of the hydraulic control valve so that the spool can slide. A spool through hole to be accommodated, a pump port having an opening formed in the valve body and opening to the spool through hole, and an opening formed in the valve body and opening to the spool through hole. An intermediate chamber, a distribution passage formed in the valve body so as to be able to communicate with the intermediate chamber, and guiding pressure oil in the intermediate chamber to the cylinder port of the hydraulic control valve; and a spool formed in the valve body. A return passage that has an opening that opens to the through-hole for use, and a return passage that guides return oil from the cylinder port to the tank port. The return passage is formed in the valve body in the vicinity of the intermediate chamber. A tank port having an opening to be opened, a first land formed in the spool and blocking between the pump port and the intermediate chamber when the spool is in a neutral position; and an outer periphery of the first land A notch formed on the surface for communicating the pump port with the intermediate chamber when the spool is moved from the neutral position by a first predetermined amount; and when the spool is in the neutral position, the intermediate chamber and the tank port And a bleed-off passage formed in the spool so as to maintain the communication state when the spool moves at least in the first predetermined amount, so that the spool is in the neutral position. The pump pressure supplied from the pump port to the intermediate chamber during the initial movement of the spool, that is, during the initial movement of the spool, is the bleed-off passage. An effect that suppresses hunting due effective and will load pressure.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 shows a longitudinal section in the spool axial direction of a main part of a hydraulic control valve 1 according to the present invention. In FIG. 1, the valve body 1A is formed with a through-hole 2A for spool that accommodates the spool 2 so as to be slidable in the left-right direction. Cylinder ports PT1 and PT2 are provided in the upper part of the valve body 1A, and are connected to relief valves RF1 and RF2 at the lower part of the respective ports. The outlet sides of the relief valves RF1 and RF2 are connected to the tank port TNP. A pilot pressure signal is applied from the left and right ends of the spool 2. A pump port P1 connected to the discharge line of the pump 10 opens into the spool through hole 2A at the center of the valve body 1A. Reference numeral P2 is an intermediate chamber opened in the spool through-hole 2A, and the intermediate chamber P2 communicates with the distribution passage PS1 via a check valve 3 disposed at the upper portion thereof. The distribution passage PS1 communicates with the line L1 when the spool 2 is moved leftward, and communicates with the line L2 when it is moved rightward.

  On the other hand, a pressure compensation valve PCVL having a chamber CH is disposed below the intermediate chamber P2, and communicates with the passage PS3 via the check valve 4 below the chamber CH. This passage PS3 communicates with a common passage 5 which is a load pressure detection line common to other hydraulic control valves. The common passage 5 constitutes a so-called load-sensing pressure oil signal, and when the pressure in the intermediate chamber P2 is higher than the pressure in the common passage 5, the pressure in the common passage 5 becomes the pressure through the check valve 4. Therefore, the common passage 5 reflects the maximum load pressure of all the other hydraulic control valves including the hydraulic control valve. Reference numerals 3A and 3B are caps.

  Reference sign PS2 is a return passage for return oil from the cylinder port PT1 or PT2, and is connected to the tank port TNP via a variable throttle portion VTH formed on the side of the pressure compensation valve PCVL. ing. Reference numeral 6 is a valve that allows return oil only in the direction from the passage PS2 to the passage PS4 when the pressure of the return passage PS2 is higher than the distribution passage PS1. When the actuator is connected so as to be in such a state, the return oil is supplied again to the cylinder port PT1 or PT2 via the distribution passage PS1, so that it does not return to the tank side, and thus has an energy saving effect.

  In the vicinity of the right side of the intermediate chamber P2, a tank port P3 opens into the spool through hole 2A. Reference numerals 7, 8, and 9 are cut portions provided on the outer peripheral surfaces of the lands R1, R2, and R3, respectively.

  FIG. 2 is a diagram for explaining the function and function of the present invention. FIG. 2A is a detailed view showing the vicinity of the intermediate chamber P2 in an enlarged manner on the upper side of the spool shaft. b) is a diagram illustrating the relationship between the spool stroke S and the flow rate flowing through the ports P1, P2, P3 and the distribution passage PS1.

  In FIG. 2A, the spool 2 is shown as being in a neutral position. Here, a case where the spool 2 moves to the right as shown by an arrow is illustrated. Therefore, in order to connect the pump port P1 and the intermediate chamber P2 to each other, the spool 2 needs to move the tip of the cut portion 7 of the land R1 to the right by at least the distance d1. On the other hand, the intermediate chamber P2 and the tank port P3 communicate with each other when in the neutral state as shown in the figure, and even if the spool 2 moves d1, the interval d2 including the cut portion 8 is formed larger. The pressure oil supplied from the port P1 to the intermediate chamber P2 flows through the small diameter portion R toward the tank port P3 rather than being supplied to the distribution passage PS1 that receives the load pressure of the actuator via the cylinder port PT2. . Further, when the spool is moved to the left, the cut portion 9 functions instead of the cut portion 8. The small diameter portion R and the cut portion 8 or the cut portion 9 and the tank port P3 constitute a bleed-off passage in the present invention.

  In FIG. 2B, the chain line curve Q0 in the graph shows the flow rate flowing from the pump port P1 through the intermediate chamber P2 to the distribution passage PS1 corresponding to the spool stroke in the conventional case where the tank port P3 is not provided. Represents. A broken line Q (P3) represents a flow rate that flows from the intermediate chamber P2 to the tank port P3 while the spool 2 moves from the neutral zero to the distance d1 and then to the position d2. Further, a curve Q indicated by a solid line represents a flow rate flowing from the intermediate chamber P2 to the distribution passage PS1 when the tank port P3 according to the present invention is provided. A chain line P-UP indicates an increase in the oil pressure in the intermediate chamber P2 corresponding to Q0. As shown in FIG. 2B, a bleed-off passage from the intermediate chamber P2 to the tank port P3 is formed in the range (d2-d1) after the initial stroke range d1 from the neutral state of the spool 2. During this stroke, the pressure in the intermediate chamber P2 is reduced by the communication with the tank port P3. Therefore, the pressure does not rise sharply as in the curve P-UP, but rises almost similar to the flow rate Q, and the heavy load pressure Is transmitted to the intermediate chamber P2 through the distribution passage PS1 and does not cause hunting.

  Although the present invention has been described above by the preferred embodiments, the present invention is not limited to the hydraulic control valve shown in FIG. 1 described above, and various modifications are possible. For example, in the hydraulic control valve 1 illustrated in FIG. 1, the circuit configuration (arranged on the meter-out side of the actuator) in which the return oil from the actuator side acts on the pressure compensation valve PCVL via the variable throttle portion VTH is shown. Even in a hydraulic control valve having a circuit configuration in which the pressure compensation valve is arranged upstream of the direction switching valve which is a hydraulic control valve or arranged downstream of the direction switching valve and on the meter-in side of the actuator, The effect is obtained as well.

The spool axial direction longitudinal cross-section of the principal part of the hydraulic control valve by this invention is shown. FIG. 2A is a detailed diagram illustrating the function of the present invention, in which FIG. 1A is an enlarged view showing the vicinity of an intermediate chamber on the upper side of the spool shaft, and FIG. It is a figure explaining the relationship between the flow volume which flows through a channel | path, and a spool stroke. It is a figure which shows the prior art example of the hydraulic control valve which comprises the hydraulic control apparatus provided with the load sensing function.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hydraulic control valve 1A Valve body 2 Spool 2A Spool through-hole 3 Check valve 3A, 3B Cap 4 Check valve 5 Common passage 6 Valve 7 Notch 8 Notch 9 Notch 10 Pump P1 Pump port P2 Intermediate chamber P3 Tank Port PS1 Distribution passage PS2 Return passage PS3 Passage PS4 Passage PCVL Pressure compensation valve R Small diameter part R1, R2, R3 Land RF1, RF2 Relief valve TNP Tank port VTH Variable throttle part

Claims (8)

In the hydraulic control valve that receives the pressure oil from the pump and supplies the pressure oil to the actuator via the cylinder port,
A spool through-hole formed in the valve body of the hydraulic control valve and slidably accommodating the spool;
A pump port having an opening formed in the valve body and opening into the spool through hole;
An intermediate chamber formed in the valve body and having an opening that opens into the spool through hole;
A distribution passage formed in the valve body so as to be able to communicate with the intermediate chamber and for guiding the pressure oil in the intermediate chamber to the cylinder port of the hydraulic control valve;
A return passage formed in the valve body and having an opening that opens into the through-hole for spool, and for returning return oil from the cylinder port to the tank port;
A tank port having an opening formed in the valve body in the vicinity of the intermediate chamber and opening to the through hole for spool;
A first land formed on the spool and blocking between the pump port and the intermediate chamber when the spool is in a neutral position;
A notch that is formed on the outer peripheral surface of the first land and communicates the pump port with the intermediate chamber when the spool is moved a first predetermined amount from its neutral position;
The spool is formed in the spool so that the intermediate chamber and the tank port are in communication with each other when the spool is in a neutral position, and at least when the spool is moved by the first predetermined amount. A bleed-off passage,
In a hydraulic control valve used in a load sensing type hydraulic control device, characterized by comprising :
The bleed-off passage has a diameter formed between a second land formed on the intermediate chamber side and a third land formed on the tank port side when the spool is in a neutral position. A hydraulic control valve for use in a load sensing type hydraulic control device having a small portion.   2. The hydraulic control valve used in a load sensing type hydraulic control device according to claim 1, wherein the tank port is formed at one location opposite to the pump port with respect to the intermediate chamber. 2. The hydraulic control valve used in the load sensing type hydraulic control device according to claim 1 , wherein a cut portion is formed on each of outer peripheral surfaces of the second land and the third land. 3. The distribution passage pressure of the load sensing system according to any one of claims 1 to 3, further comprising a check valve on the way the distribution passages are formed disposed on one side of the spool center axis Hydraulic control valve used in the control device. It said return hydraulic control valve passage to be used in the hydraulic control device for the load-sensing system according to any one of claims 1 to 4, characterized in that it has been formed disposed on the other side of the spool center axis. In the valve body of the hydraulic control valve, a common passage for guiding the load pressure of another hydraulic control valve constituting the hydraulic control device is formed. The common passage and the intermediate chamber are connected via a check valve. The hydraulic control valve used in the load sensing type hydraulic control device according to any one of claims 1 to 5 , wherein the hydraulic control valve is connected in communication. 7. The hydraulic control valve used in the load sensing type hydraulic control device according to claim 6 , wherein a pressure compensation valve is formed and arranged on a connection passage that is connected in communication via the check valve. The return to the passage provided with a check valve, either the passage for supplying the return fluid from said reverse valve in the dispensing passage side of claims 1 to 7, characterized in that formed in the valve body A hydraulic control valve used in the load sensing type hydraulic control device described.

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