JP3062862B2 - Negative flow control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a negative flow control device provided with a negative flow control relief valve, which is applied to a construction machine such as a hydraulic excavator.

[0002]

2. Description of the Related Art A conventional negative flow control device having a negative flow control relief valve will be described with reference to FIG. The variable displacement pump 100 and the oil tank T
It is connected via a bypass oil passage 102. A negative flow control relief valve 104 is arranged at the most downstream of the bypass oil passage 102. Although several operation valves are arranged in the bypass oil passage 102, the operation valve 106 shown in the figure indicates the operation valve located at the most downstream side thereof. Operating valve 10
6 and the negative flow control relief valve (negative control relief valve) 104
It is provided in. A spool 110 of the operation valve 106 is disposed on the valve casing 108 so as to be movable in the left-right direction. The spool 110 is positioned at a neutral position by a spring 112 provided on the right end side. Pilot ports 112 and 114 are formed in the valve casing 108 so that pilot secondary pressure acts on both left and right ends of the spool 110, respectively. The opening and closing of the bypass oil passage 102 formed in the valve casing 108 is controlled by spool lands 110 a and 110 b of the spool 110.

[0003] The negative flow control relief valve 104 is
It includes a cylindrical body 116 and a surge pressure cut relief valve poppet 118 provided in the body 116. The body 116 has a plurality of negative flow control signal generating orifices 1 communicating with the oil tank passage 122.
20 are formed. The body 116 has a surge pressure cutting oil passage communicating with the oil tank passage 122. Surge pressure cut relief valve poppet 118
Normally closes this oil passage by a spring. As is apparent from the above configuration, the bypass oil passage 102 is connected to the oil tank passage 122 through the orifice 120, and is connected to the oil tank via a surge pressure cut oil passage normally closed by the poppet 118. It is connected to passage 122. A negative flow control signal port 103 is formed upstream of the orifice 120 in the bypass oil passage 102. On the other hand, the variable displacement pump 100 is provided with a known displacement control mechanism (not shown). Signal port 1
Numeral 03 is connected to a negative control mechanism of the capacity control mechanism via a signal transmission oil passage 123. The number 124
Reference numeral 126 denotes an oil passage to a specific actuator (not shown) controlled by the operation valve 106, and reference numeral 126 denotes a load hold check valve provided in the oil passage 124.

[0004]

The bypass oil passage 102 is fully opened when all the operation valves including the operation valve 106 are in neutral,
The entire discharge pressure oil of the variable displacement pump 100 flows into the negative flow control relief valve 104, and flows out to the oil tank T through the negative flow control signal generation orifice 120. The hydraulic pressure at the negative flow control signal port 103 becomes maximum, and this signal is transmitted to the negative control mechanism of the variable displacement pump 100 via the signal transmission oil passage 123, and the discharge oil amount (flow rate) of the variable displacement pump 100 is restricted to the minimum. Is done. This state is indicated by a balance point A in FIG. That is, the balance point A becomes the lowest as the discharge flow rate of the pump 100 (solid line in FIG. 6) decreases, and the flow rate through the negative flow control relief valve 104 (dotted line in FIG. 6).
Increase to a maximum, indicating that both are balanced.

Referring to FIGS. 5 and 6, when the operation lever (control lever) of the remote control valve (not shown) is finely operated, for example, a pilot secondary pressure acts on the pilot port 114 on the right side of FIG. . The spool 110 of the operation valve 106 moves to the left in FIG.
By the left end of the spool land 110a, the bypass oil passage 10
2, the discharge pressure of the pump 100 starts to increase.
However, until the discharge pressure reaches the load pressure of the actuator, pressure oil is not supplied to the actuator (pressure oil does not flow into the actuator), and the entire amount flows into the negative flow control relief valve 104. I do. Therefore, the negative flow control signal pressure transmitted to the negative control mechanism of the pump 100 is still the value corresponding to the point A in FIG. 6, and the discharge flow rate of the pump 100 also maintains the value corresponding to the minimum balance point A. .

When the load pressure of the actuator is relatively low, the narrowing of the bypass oil passage 102 by the left end of the spool land 110a of the spool 110 is relatively small, so that the pump 100 has a relatively large opening.
Discharge pressure rises to the load pressure of the actuator. That is, when the load pressure of the actuator is relatively low,
The spool stroke (stroke of the spool 110) of the operation valve 106 required until the discharge pressure of the pump 100 reaches the load pressure of the actuator is relatively small. Therefore, when the opening degree of the bypass oil passage 102 is further reduced, the pressure oil is supplied to the actuator, and the flow rate passing through the negative flow rate control relief valve 104 decreases. The discharge pressure of the pump 100 gradually increases, and pressure oil corresponding to the height indicated by the arrow in FIG. 6 is supplied to the actuator. For example, when the bypass oil passage 102 is operated from the fully closed state to the fully open state, the response of the pump 100 causes a large flow rate transiently when the pump 100 is neutral (when the operation valve 106 is neutral). Oil is negative flow control relief valve 1
It rushes to 04. Since this flow rate cannot be absorbed only by the orifice 120, a peak pressure is generated and the life of the device is shortened. In order to prevent such a problem, a surge pressure cut relief valve poppet 118 is provided. In the above case, the poppet 118 is opened to discharge excess oil to the oil tank T. The right end of the dotted line in FIG. 6 indicates this state.

On the other hand, when the load pressure of the actuator is relatively high, the narrowing of the bypass oil passage 102 is relatively large.
The discharge pressure of 0 rises to the load pressure of the actuator. That is, when the load pressure of the actuator is relatively high, the spool stroke (stroke of the spool 110) of the operation valve 106 required until the discharge pressure of the pump 100 reaches the load pressure of the actuator is relatively large. Therefore, when the opening degree of the bypass oil passage 102 is further reduced, the pressure oil is supplied to the actuator, and the pressure oil corresponding to the height indicated by the arrow in FIG. 6 is supplied to the actuator by the same mechanism as described above.

As described above, according to the conventional negative flow control device including the negative flow control relief valve 104, if the load on the actuator is low, the operation valve 106
Actuator starts with a small spool stroke,
When the load on the actuator is high, the spool stroke is large and the actuator starts. Therefore, this device
As shown in FIG. 7, there is a disadvantage that the load pressure is not compensated due to the influence of the load pressure of the actuator. That is, since the spool stroke (operation stroke of the operation lever) until the actuator is started differs depending on the magnitude of the load on the actuator, the operability when the operation valve is finely operated by the operation lever varies, resulting in poor operability. ,
There is a problem that accurate operation becomes difficult and the burden of operation labor increases.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved negative flow control device capable of keeping the spool stroke of the operation valve substantially constant until the actuator is started, regardless of the magnitude of the load on the actuator. It is.

[0010]

According to the present invention, the discharge pressure oil of the variable displacement pump is arranged at the most downstream of the bypass oil passage and is neutralized to the oil tank through the negative flow control signal generating orifice when the operation valve is in neutral. In a negative flow control device comprising a negative flow control relief valve configured to flow out, the negative flow control relief valve comprises:
A negative flow control signal generating oil passage that communicates the inlet connected to the bypass oil passage with the negative flow control signal generating orifice; and a load pressure compensating valve arranged to close the negative flow control signal generating oil passage by a spring. A main poppet, a load pressure compensating pilot oil passage connecting the inlet and the oil tank, a load pressure compensating valve pilot stage poppet arranged to open and close the load pressure compensating pilot oil passage, and the load pressure compensating valve A solenoid means including a proportional solenoid coil for applying a thrust to the pilot stage poppet in a direction to close the pilot oil passage, wherein the load pressure compensating valve pilot stage poppet has a function of the variable displacement pump acting when the operation valve is in neutral. The discharge pressure oil opens the load pressure compensation pilot oil passage, and the load pressure compensation valve main poppet is Is configured to open the negative flow rate control signal generating oil path according to come the open of Ni圧 compensating valve pilot stage poppet, the proportional solenoid coil,
The control valve is connected to control means for supplying a current corresponding to the load pressure of the load side chamber of the actuator connected to the operation valve, and the control means is configured to switch the operation valve to the load side chamber of the actuator when the operation valve is switched to the load side chamber. By supplying a current corresponding to the load pressure of the actuator to the proportional solenoid coil to apply a thrust to the load pressure compensating valve pilot stage poppet in the direction to close the load pressure compensating pilot oil passage, the inlet of the actuator is A negative flow control device is provided which is configured to generate a pressure corresponding to a load pressure.

[0011]

When the operation valve is neutral, the load pressure compensating valve pilot stage poppet opens the load pressure compensating pilot oil passage by the discharge pressure oil of the variable displacement pump supplied from the bypass oil passage to the inlet of the negative flow control relief valve. The discharge pressure oil of the variable displacement pump is discharged to the oil tank through the pilot oil passage. The generation of the pilot drain causes the main poppet of the load pressure compensating valve to open the negative flow control signal generating oil passage. The discharge pressure oil of the variable displacement pump supplied to the inlet flows out to the oil tank through a negative flow control signal generating oil passage and a negative flow control signal generating orifice. When the operation valve is switched from the neutral state to the load side chamber of the actuator, a current corresponding to the load pressure of the load side chamber of the actuator connected to the operation valve is supplied from the control means to the proportional solenoid coil. Since a thrust in the direction of closing the pilot oil passage is applied to the load pressure compensating valve pilot stage poppet, a pressure corresponding to the load pressure of the actuator is generated at the inlet. Therefore, when the bypass valve is narrowed to a certain level by the operating valve until the supply passage of the actuator starts to be opened regardless of the magnitude of the load on the actuator (that is, the operating valve is switched from the neutral state to a certain level). Is reached), the discharge pressure oil of the variable displacement pump is always maintained at or above the load pressure of the actuator. That is, the spool stroke of the operation valve until the actuator starts is substantially constant. As a result, the operability when the operation valve is finely operated by the operation lever is stabilized, more accurate operation can be performed, the operability is improved, and the operation labor is reduced.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, an embodiment of a negative flow control device 1 having a negative flow control relief valve with a load pressure compensation function improved according to the present invention will be described. In the bypass oil passage 4 connecting the variable displacement pump 2 and the oil tank T, an operation valve 6 known per se and a new negative flow control relief valve 8 with a load pressure compensation function configured according to the present invention are arranged. I have. Although a plurality of operation valves are generally arranged in the bypass oil passage 4, only the operation valve 6 arranged at the most downstream position is shown here. The negative flow control relief valve 8 is connected to the bypass oil passage 4.
Is located at the most downstream of The operation valve 6 is connected to the actuator 10. The actuator 10 includes a cylinder 12 and a piston 14 disposed in the cylinder 12. A piston rod 16 is connected to the piston 14, and a weight load W acts on the piston rod 16. The cylinder 12 is divided by a piston 14 into a load side chamber (cylinder head side chamber) 18 and a non-load side chamber (piston rod side chamber) 20. Load side chamber 18
, A load pressure due to the weight load W is acting. FIG.
The operation valve 6, which may have substantially the same configuration as the operation valve 106 described in the above, has a neutral position (FIG. 1) for supplying the discharge pressure oil of the variable displacement pump 2 to the negative flow control relief valve 8 via the bypass oil passage 4. (A position shown in FIG. 5), a switching position (function) 6a for supplying discharge pressure oil to the load side chamber 18 of the actuator 10 and a discharge position
Is switched to the switching position 6b for supplying to the non-load-side chamber 20. Switching from the neutral position of the operation valve 6 is performed by operating a pilot lever of a remote control valve (not shown) to apply a pilot secondary pressure to pilot ports provided on both sides of the operation valve 6.

[0013] The negative flow control relief valve 8 includes a sleeve member 22 having a substantially cylindrical shape. The valve casing 24 (the valve casing 108 shown in FIG. 5)
The through-hole 26 is formed in the sleeve member 22 which is detachably mounted with a screw from the right end (one end) to the left end (the other end). The through hole 26 has a common central axis with the sleeve member 22. The right end of the through hole 26 forms an inlet 28 connected to the bypass oil passage 4. A substantially cylindrical sheet member 30 is fitted (mounted) on the outer peripheral portion of the inlet 28 of the sleeve member 22 so as not to move. A hole 5 communicating with the bypass oil passage 4 is formed in the valve casing 24, and the seat member 30 is inserted into the hole 5 via the seal member 7. On the left side of the hole 5 of the valve casing 24, a space 9 which is continuous with the hole 5 but is partitioned by the sealing member 7 is formed. The space 9 communicates with the oil tank T. The inner diameter of the left end (one end) of the sheet member 30 is formed to be larger than the outer diameter of the corresponding outer peripheral portion of the sleeve member 22. Therefore, an annular space 32 having an open left end is formed between the inner peripheral portion of the left end portion of the sheet member 30 and the outer peripheral portion of the sleeve member 22. Sheet member 3
A surge pressure cut relief valve poppet 34 having a substantially cylindrical shape is mounted on the left side of 0 and on the outer peripheral portion of the sleeve member so as to be movable in the axial direction. The surge pressure cut relief valve poppet 34 is biased rightward by a spring 35 to close the left end of the seat member 30. Thereby, the space 32 forms the pressure chamber 32. A negative flow control signal generating orifice 36 is formed at the left end of the seat member 30 such that one end opens to the pressure chamber 32 and the other end opens to the outer periphery of the seat member 30.
A plurality of orifices 36 are formed, each having a radial axis.

A discharge hole 38 is formed in the sleeve member 22 so as to communicate the pressure chamber 32 and the through hole 26. A plurality of discharge holes 38 are formed, each of which has a radial axis. Inlet 28 and outlet 3 of through-hole 26
8, a valve seat portion 40 is formed.
On the left side (downstream side) of the valve seat portion 40 of the through hole 26, a load pressure compensating valve main poppet 42 having a substantially cup shape is disposed so as to be movable in the axial direction. As shown in the figure, the inside diameter of the through hole 26 at the portion where the discharge hole 38 opens (left side of the valve seat portion 40) is formed slightly larger than the inside diameter of the left and right sides. Through hole 26
On the left side (downstream side), a pilot stage seat member 44 is mounted so as not to move. A spring 46 is interposed between the pilot stage seat member 44 and the load pressure compensating valve main poppet 42. The load pressure compensating valve main poppet 42 is biased rightward by a spring 46 to close the valve seat portion 40. Between the valve seat portion 40 and the load pressure compensating valve main poppet 42, the discharge hole 38 and the pressure chamber 32 are connected to the inlet 28.
A negative flow control signal generating oil passage which communicates with the orifice 36 is formed. Load pressure compensator main poppet 42
An orifice 48 having one end opening toward the inlet 28 and the other end opening downstream is formed on the wall defining the right end of the orifice. An oil passage 50 is formed in the pilot stage seat member 44, one end of which opens toward the load pressure compensating valve main poppet 42 and the other end opens downstream of the pilot stage seat member 44. One end of the sleeve member 22 is provided with a pilot stage seat member 44 having a through hole 26 at one end.
A pilot discharge port 52 is formed such that the pilot discharge port 52 is opened on the downstream side and the other end is opened on the outer peripheral portion of the sleeve member 22.

A load pressure compensating valve pilot stage poppet 54 is disposed in the through hole 26 downstream of the pilot stage seat member 44 so as to be movable in the axial direction. Load pressure compensator pilot stage poppet 54
Are positioned so that the oil passage 50 of the pilot stage seat member 44 can be opened and closed. Between the orifice 48 and the oil passage 50, the left end of the oil passage 50 and the pilot stage seat member 44, the pilot outlet 52 and the like form a load pressure compensating pilot oil passage connecting the inlet 28 and the oil tank T. At the left end of the sleeve member 22, a solenoid means 60 including a proportional solenoid coil 56 and an iron core 58 for applying a thrust to the load pressure compensating valve pilot stage poppet 54 in the direction to close the oil passage 50 (to the right in FIG. 1). Is installed. A push pin 62 is integrally provided on the right end side of the iron core 58. Push pin 62
Is movably disposed in the left end of the through hole 26, and constitutes a thrust transmitting member for transmitting the thrust of the iron core 58 to the load pressure compensating valve pilot stage poppet 54. The solenoid means 60 includes a proportional solenoid coil 56 and an iron core 58.
And a case 64 that covers a part of the push pin 62. As shown in FIG. 1, with the right end of the push pin 62 abutting on the left end of the load pressure compensating valve pilot stage poppet 54, and with the load pressure compensating valve pilot stage poppet 54 closing the oil passage 50, A gap is formed between both ends in the case 64. The gap between the left end of the iron core 58 and the left end in the case 64 is such that when the discharge pressure oil of the variable displacement pump 2 acts on the oil passage 50, the load pressure compensating valve pilot stage poppet 54 moves leftward to It is provided so that the road 50 can be opened. Reference numeral 23 denotes a spacer, which is disposed in the through hole 26 between the case 64 and the pilot stage seat member 44.

Referring to FIG. 1 as well as FIG. 2, two negative flow control signal transmission grooves 66 extending in the axial direction are formed in the inner peripheral portion of the relief valve 34 for cutting surge pressure. An annular groove 68 is formed on the outer periphery of the sleeve member 22 corresponding to the left end of the negative flow control signal transmission groove 66. The sleeve member 22 is also provided with a negative flow control signal transmission hole 70 which is parallel to the central axis and whose right end is open to the annular groove 68. At the left end of the sleeve member 22, a negative flow control signal port 72 is formed, one end of which is open to the outer periphery and the other end is open to the left end of the negative flow control signal transmission hole 70. The negative flow control signal transmission groove 66, the annular groove 68, and the negative flow control signal transmission hole 70 form a negative flow control signal transmission path connecting the pressure chamber 32 and the negative flow control signal port 72. The signal port 72 is connected to a negative control mechanism of the variable displacement pump 2 via a signal transmission oil passage 73. Negative flow control relief valve 8
, The seat member 30, the surge pressure cut-off relief valve 34, the load pressure compensating valve main poppet 42, the pilot stage seat member 44, the load pressure compensating valve pilot stage poppet 54, the solenoid means 60, and the push pin 62 are substantially The relief valve 8 is arranged on the central axis (on the same axis). That is, in the negative flow control relief valve 8, the load pressure compensating valve is disposed substantially on the same axis as the conventional valve having the negative flow control relief valve function. Therefore, according to the present invention, a combination type compact negative flow control relief valve having a load pressure compensation function can be obtained.

The load pressure compensating valve pilot stage poppet 54 opens an oil passage 50 which is a part of the load pressure compensating pilot oil passage by the discharge pressure oil of the variable displacement pump 2 acting when the operation valve 6 is in the neutral position. The main poppet 42 is configured to open the valve seat 40 which is a part of the negative flow control signal generating oil passage in response to the opening of the load pressure compensating valve pilot stage poppet 54. The proportional solenoid coil 56 is connected to control means 80 for supplying a current according to the load pressure of the load side chamber 18 of the actuator 10 connected to the operation valve 6. When the operation valve 6 is switched to the load-side chamber 18 of the actuator 10, the control means 80 controls the proportional solenoid coil 5
6 is supplied with a current corresponding to the load pressure of the actuator 10 (the load pressure of the load-side chamber 18) to apply a thrust in the direction of closing the oil passage 50 to the load pressure compensating valve pilot stage poppet 54, so that the actuator 28 A pressure equivalent to 10 load pressures is generated.

The negative flow control device 1 further includes a pressure switch 81 for detecting that the operating valve 6 has been switched to the load side chamber 18 of the actuator 10 and a pressure sensor 8 for detecting the load pressure of the load side chamber 18 of the actuator 10.
2 is provided. The pressure switch 81 is an ON-OFF switch, and constitutes an operation valve switching detection unit. The pressure switch 81 is connected to a pilot oil passage 83 that switches the operation valve 6 from the neutral position to the switching position 6a. The pilot oil pressure is supplied to the pilot oil passage 83 when an operation lever of a remote control valve (not shown) is operated. The pressure sensor 82 constitutes a load pressure detecting means. The control means 80 is configured to supply a current corresponding to the load pressure of the load-side chamber 18 to the proportional solenoid coil 56 based on signals from the pressure switch 81 and the pressure sensor 82. More specifically, the control means 80 includes an AND circuit 80a. The AND circuit 80a is connected to the pressure switch 81,
It is connected to a pressure sensor 82 via an A / D (analog / digital) converter 80b and a preamplifier 80c. The AND circuit 80a is a D / A (digital / analog) converter 80
d, connected to a current amplifier 80f via a gain adjustment circuit 80e. The current amplifier 80f is connected to the proportional solenoid coil 56 so that it can supply an amplified current. The current amplifier 80f also includes a null adjustment circuit 80.
g, another current amplifier 80h including a dither frequency determination circuit
It is connected to the. As is apparent from the above configuration, the control means 80 detects that the operation valve 6 has been switched to the load-side chamber 18 to which the pressure sensor 82 is connected (switched to the function 6a in FIG. 1). The signal and the signal from the pressure sensor 82 for detecting the load pressure of the load side chamber 18 of the actuator 10 are processed. More specifically, the control means 80
Supplies the signal corresponding to the load pressure of the load side chamber 18 of the actuator 10 of the pressure sensor 82 to the proportional solenoid coil 56 in a form of current amplification only when an operation signal of the pressure switch 81 is input. is there.

Next, the operation of the negative flow control device 1 configured as described above will be described. Operation valve 6
Is neutral, the discharge pressure oil of the variable displacement pump 2 supplied from the bypass oil passage 4 to the inlet 28 of the negative flow control relief valve 8 is first supplied to the oil passage 50 through the orifice 48. As a result, the load pressure compensating valve pilot stage poppet 54 is opened. The pressure oil supplied to the oil passage 50 flows out to the oil tank T through the pilot outlet 52. This generation of the pilot drain opens the load pressure compensating valve main poppet 42. The discharge pressure oil supplied to the inlet 28 flows out to the oil tank T through the discharge hole 38, the pressure chamber 32, the negative control signal generation orifice 36 and the space 9. A negative flow control signal is generated in the pressure chamber 32. The negative flow control signal is transmitted to the negative flow control signal transmission groove 66 and the annular groove 6.
8, transmitted to the negative control mechanism of the variable displacement pump 2 via the negative flow control signal transmission hole 70, the negative flow control signal port 72, and the signal transmission oil passage 73. Thereby, the variable displacement pump 2 is negatively controlled.

When the operation lever of the remote control valve (not shown) is finely operated to switch the operation valve 6 in the neutral state to the load side chamber 18 of the actuator 10, a pilot secondary pressure is supplied to the pilot oil passage 81. You. This switching operation signal is input from the pressure switch 81 to the control means 80. As a result, a proportional current corresponding to the load pressure of the load side chamber 18 of the actuator 10 connected to the operation valve 6 is supplied from the control means 80 to the proportional solenoid coil 56 of the negative flow control relief valve 8. A corresponding magnetic force is generated in the solenoid means 60, and a thrust for forcibly moving the iron core 58 to the right is generated. This thrust is transmitted to the load pressure compensating valve pilot stage poppet 54 via the push pin 62. This is the pressing force of the pilot stage seat member 44 against the opening of the oil passage 50. That is, since a thrust in the direction of closing the oil passage 50 is applied to the load pressure compensating valve pilot stage poppet 54, the load pressure compensating valve main poppet 4
A pressure corresponding to the load pressure of the actuator 10 is generated at the inlet 2 of the valve 2, that is, at the inlet 28 of the negative flow control relief valve 8. Such adjustment is performed by the current gain adjustment circuit 80e of the control means 80.

Therefore, when the bypass oil passage 4 is narrowed down to a certain level by the operation valve 6 until the supply passage of the actuator 10 starts to open regardless of the magnitude of the load on the actuator 10 (ie, the operation valve 6). Is switched from the neutral state to the switching position 6a and reaches a certain spool stroke), the variable displacement pump 2
Discharge pressure oil is always supplied to the load side chamber 18 of the actuator 10.
Is maintained above the load pressure. In other words, the stroke of the operating valve 6 is determined by the stroke of the operating lever after that point.
When the well-known metering slot, from which the pressure oil starts to be supplied from the variable displacement pump 2 to the actuator supply passage, starts to open, the pressure oil is supplied to the actuator 10.
That is, the operating valve 6 until the actuator 10 starts
Is substantially constant regardless of the magnitude of the load on the actuator 10 (see FIG. 4). As a result, the operability when finely operating the operation valve 6 with the operation lever becomes stable and accurate, and the operability is improved and the operation labor is reduced. The function of the surge pressure cut relief valve poppet 34 is substantially the same as the function of the surge pressure cut relief valve poppet 118 described with reference to FIG.

Next, another embodiment of the negative flow control relief valve with a load pressure compensating function according to the present invention will be described with reference to FIG. A negative flow control relief valve with a load pressure compensating function, which is generally designated by reference numeral 90, is substantially different from the negative flow control relief valve with a load pressure compensating function 8 described with reference to FIG. Since the other configuration is substantially the same as that of the negative flow control relief valve 8, the same portions are denoted by the same reference numerals and description thereof will be omitted. The overall function of the negative flow control relief valve 90 is substantially the same as that of the negative flow control relief valve 8. An annular groove 92 is formed in an outer peripheral portion of the sleeve member 22 facing the pressure chamber 32 so as to communicate the discharge hole 38 and the pressure chamber 32. The sleeve member 22 is formed with a negative flow control signal transmission hole 94 which is parallel to the central axis and one end of which is opened in the annular groove 92. One end of the negative flow control signal port 72 is open at the left end of the negative flow control signal transmission hole 92, and the other end is the sleeve member 22.
Is formed so as to open to the outer peripheral portion of. A negative flow control signal transmission path connecting the pressure chamber 32 and the negative flow control signal port 72 is configured by an annular groove 92 and a negative flow control signal transmission hole 94. According to this configuration, the two negative flow control signal transmission grooves 66 formed in the inner peripheral portion of the surge pressure cut relief valve poppet 34 in the negative flow control relief valve 8 are eliminated. Therefore, workability is improved and manufacturing cost is reduced.

The embodiment of the negative flow control device provided with the negative flow control relief valve with the load pressure compensating function according to the present invention has been described above. However, the present invention is not limited to the above embodiment, and the present invention is not limited thereto. Various changes or modifications can be made without departing from the scope of the above. For example, in the embodiment, the present invention has been described in relation to the operation valve 6 located at the most downstream side of the pilot oil passage 4, but the present invention may be applied in connection with another operation valve (not shown). However, it may be applied in connection with a plurality of operation valves at the same time.
In one embodiment, the pressure sensor 82 is
Is provided in association with the load-side chamber 18 which is a cylinder head-side chamber, but the load-side chamber may be a piston rod-side chamber depending on the form of the actuator. In that case,
The pressure sensor 82 is provided in association with the piston rod side chamber.

[0024]

According to the negative flow control device having the negative flow control relief valve with the load pressure compensating function constructed according to the present invention, regardless of the magnitude of the load on the actuator, the operation of the operating valve until the actuator is started is started. The spool stroke can be made substantially constant.
As a result, the operability when the operation valve is finely operated by the operation lever becomes stable and accurate, and the operability is improved and the operation labor is reduced. Further, according to the negative flow control relief valve with the load pressure compensating function included in the negative flow control device constituted according to the present invention, the load pressure compensating valve is provided on substantially the same axis as the conventional valve having the negative flow control relief valve function. Is arranged. Therefore, according to the present invention, a combination type compact negative flow control relief valve having a load pressure compensation function can be obtained.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing an embodiment of a negative flow control device having a negative flow control relief valve with a load pressure compensation function improved according to the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG. 1;

FIG. 3 is a sectional view showing another embodiment of a negative flow control relief valve with a load pressure compensation function improved according to the present invention.

FIG. 4 is a diagram showing the characteristics of a negative flow control device having a negative flow control relief valve with a load pressure compensation function improved according to the present invention, wherein the operation valve spool stroke and the supply flow rate of the pressure oil to the actuator; FIG.

FIG. 5 is a cross-sectional view of a conventional valve casing provided with a negative flow control relief valve and an operation valve.

FIG. 6 is a diagram showing a relationship among a hydraulic pump discharge flow rate, a negative flow control relief valve passage flow rate, and a negative flow control signal pressure.

FIG. 7 is a diagram showing characteristics of a conventional negative flow control device provided with a negative flow control relief valve, and is a diagram showing a relationship between a control valve spool stroke and a supply flow rate of pressure oil to an actuator.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 negative flow control device 2 variable displacement pump 4 bypass oil passage 6 operating valve 8 negative flow control relief valve 10 actuator 18 load side chamber 22 sleeve member 26 through hole 28 inlet 30 seat member 32 pressure chamber 34 relief valve for surge pressure cut 36 negative Flow control signal generating orifice 38 Discharge hole 42 Load pressure compensating valve main poppet 44 Pilot stage seat member 48 Orifice 50 Oil passage 52 Pilot discharge port 54 Load pressure compensating valve pilot stage poppet 56 Proportional solenoid coil 58 Iron core 60 Solenoid means 62 Push pin 66 Negative flow control signal transmission groove 68 Annular groove 70 Negative flow control signal transmission hole 72 Negative flow control signal port 73 Signal transmission oil passage 80 Control means 81 Pressure Switch 82 pressure sensor 80f current amplifier 90 negative flow control relief valve 92 annular groove 94 negative flow control signal transmission hole

Claims (4)

(57) [Claims] 1. A negative flow control relief disposed at the most downstream of a bypass oil passage and configured to cause a discharge pressure oil of a variable displacement pump to flow out to an oil tank via a negative flow control signal generating orifice when a control valve is in a neutral state. In a negative flow control device including a valve, the negative flow control relief valve includes a negative flow control signal generation oil passage that communicates an inlet connected to the bypass oil passage and the negative flow control signal generation orifice;
A load pressure compensating valve main poppet arranged to close the negative flow control signal generating oil passage by a spring, a load pressure compensating pilot oil passage connecting the inlet and the oil tank,
A load pressure compensating valve pilot stage poppet arranged to open and close the load pressure compensating pilot oil passage; and a proportional solenoid coil for applying a thrust to the load pressure compensating valve pilot stage poppet in a direction to close the pilot oil passage. The load pressure compensating valve pilot stage poppet opens the load pressure compensating pilot oil passage by the discharge pressure oil of the variable displacement pump that operates when the operation valve is neutral, and the load pressure compensating valve main poppet Is configured to open the negative flow control signal generation oil passage in response to the opening of the load pressure compensating valve pilot stage poppet, and the proportional solenoid coil is configured to adjust a load pressure of a load side chamber of an actuator connected to the operation valve. Connected to control means for supplying a corresponding current, the control means comprising: When switching to the load side chamber of the actuator, a current corresponding to the load pressure of the actuator is supplied to the proportional solenoid coil to close the load pressure compensating pilot oil passage to the load pressure compensating valve pilot stage poppet. A negative pressure control device, wherein a pressure corresponding to a load pressure of the actuator is generated at the inlet by applying the thrust. 2. An operating valve switching detecting means for detecting that the operating valve is switched to the load side chamber of the actuator, and a load pressure detecting means for detecting the load pressure of the load side chamber of the actuator. 2. The negative flow control device according to claim 1, wherein said control means supplies said current to said proportional solenoid coil based on signals from both said control valve switching detection means and said load pressure detection means. 3. A substantially cylindrical sleeve member which is formed so as to pass through a central axis from one end to the other end and has a through hole at one end side of which forms the inlet. A substantially cylindrical sheet member mounted on the outer periphery of the inlet of the sleeve member so as to form an annular space open at one end with the outer periphery of the sleeve member; and the one end of the sheet member A surge pressure cut relief valve poppet mounted on the outer periphery of the sleeve member so that the space becomes a pressure chamber by closing the spring with a spring, and one end opened to the pressure chamber and the other end opened to the outer periphery. A negative flow control signal generating orifice formed in the sheet member; a discharge hole formed in the sleeve member to communicate the pressure chamber with the through hole; and a pressure chamber and the discharge hole. Ne An oil passage for generating a gative flow control signal,
An oil disposed in the through hole so as to close a valve seat portion formed in the through hole between the inlet and the discharge hole by a spring, and having one end opened to the inlet side and the other end opened to the downstream side. A load path compensating valve main poppet having a passage formed therein, a pilot stage seat member disposed in the through hole at a downstream side of the load pressure compensating valve main poppet and having an oil path formed therein, one end of which is provided with the through hole; A pilot discharge port formed in the sleeve member such that a hole is opened on the downstream side of the pilot stage seat member and the other end is opened on an outer peripheral portion of the sleeve member; the load pressure compensating valve main poppet and the pilot stage; A load pressure compensating pilot oil passage including the oil passage and the pilot discharge port respectively formed in the seat member for the pilot, and the pilot passage downstream of the seat member for the pilot stage. A load pressure compensating valve pilot stage poppet that is disposed in a hole and that can open and close the oil passage of the pilot stage seat member; and a proportional solenoid coil and an iron core mounted on the other end of the sleeve member. A thrust transmitting member movably disposed in the through hole and transmitting the thrust of the iron core to the load pressure compensating valve pilot stage poppet; and a negative flow control signal port formed in the sleeve member. And a negative flow rate control signal transmission path connecting the pressure chamber and the negative flow rate control signal port, the seat member, the surge pressure cut-off relief valve, the load pressure compensating valve main poppet, and the pilot stage. A seat member, the load pressure compensation valve pilot stage poppet,
2. The negative flow control device according to claim 1, wherein said solenoid means and said thrust transmitting member are disposed substantially on said central axis. 4. An annular groove communicating with the discharge hole and the pressure chamber is formed in an outer peripheral portion of the sleeve member facing the pressure chamber, and the sleeve member is parallel to the central axis. A negative flow control signal transmission hole is formed, one end of which is open to the annular groove, the negative flow control signal port has one end opened to the negative flow control signal transmission hole, and the other end is formed on the outer peripheral portion of the sleeve member. The negative flow control device according to claim 2, wherein the negative flow control signal transmission path is formed to be open, and the negative flow control signal transmission path is constituted by the annular groove and the negative flow control signal transmission hole.