JPH04136508A - Control valve for hydraulic circuit - Google Patents

Abstract

PURPOSE:To prevent the hunting simply to enhance the responsiveness of a hydraulic circuit by drilling oil lines for feeding the output pressure oil to a load sensing inlet circuit and for feeding to and shutting it off from a tank port in a spool for connecting and shutting off the input/output ports. CONSTITUTION:The one end portion of an axial hole 50 in the spool 42, which connects and shuts off inlet and outlet ports 45 and 46 of a valve body 40, is opened to the external surface of the body through a line 51, the middle portion of it is opened to a small diameter portion 44 through a small hole 52, and the other end portion is opened to the external surface of it through a small hole 53. Also, the inlet of a shuttle valve 21 in the valve body 40 or a load sensing inlet circuit 30 is opened to a port 49 of a spool hole 41. With the spool 42 positioned at neutral, the line 51 is connected to the port 49 and the small hole 53 is connected to a tank port 48. Thus, the responsiveness of the variation in pump capacity to the variation in opening area of a control valve 15 is declined to prevent the hunting, thus the control valve can be simplified in construction and a bypass valve can be obviated.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an operating valve used in a hydraulic circuit that supplies pressure oil discharged from one hydraulic pump to a plurality of hydraulic actuators.

[Conventional technology]

In order to supply pressure oil discharged from one hydraulic pump to multiple hydraulic actuators, it is sufficient to provide multiple operating valves in the discharge path of the hydraulic pump and supply pressure oil to each hydraulic actuator by switching the operating valves. However, in this case, when pressure oil is supplied to a plurality of hydraulic actuators at the same time, pressure oil is supplied only to the hydraulic actuators with a small load, and no pressure oil is supplied to the hydraulic actuators with a large load.

For example, a hydraulic circuit shown in FIG. 4 has been proposed as a hydraulic circuit that solves this problem.

That is, the hydraulic pump 10 is a variable displacement hydraulic pump in which the displacement, that is, the discharge flow rate per rotation, is changed by changing the angle of the swash plate 11, and the swash plate 11 is tilted in the direction of decreasing capacity by the large diameter piston 12. Then, the small diameter piston 13 tilts in the direction of increasing capacity.

The pressure receiving chamber 12a of the large diameter piston 12 is communicated with and cut off from the discharge passage 10g of the hydraulic pump 10 by a switching valve 14, and the pressure receiving chamber 13a of the small diameter piston 13 is connected to the discharge passage 10g.

A plurality of operation valves 1 are provided in the discharge passage 10a of the hydraulic pump 10.
5 are provided, each operating valve 15 and hydraulic actuator 1
A pressure compensation valve 18 is provided in each of the circuits 17 connecting 6, and the pressure compensation valves 18 are pushed to the low pressure set side by the pressure oil of the first pressure receiving part 19, and are pushed to the high pressure set side by the pressure oil of the second pressure receiving part 20. The first pressure receiving part 19 is connected to the outlet side of the operation valve 15 and is supplied with outlet side pressure, and the second
The pressure receiving section 20 is connected to each circuit 17 via a shuttle valve 21 and is supplied with the highest load pressure.

The switching valve 14 is pushed in the communication direction by the pressure in the discharge passage 10a, and pushed in the drain direction by the spring 22 and the load pressure, so that when the discharge pressure P1 increases, the discharge pressure is applied to the pressure receiving chamber 12a of the large diameter piston 12. When the discharge pressure P becomes low, the pressure receiving chamber 12a of the large diameter piston 12 flows out to the tank side, and the swash plate 11 is tilted in the direction of increasing the capacity.

The operation valve 15 is operated in a direction in which the opening area increases in proportion to the pilot pressure oil from the pilot control valve 23,
The pilot pressure oil is proportional to the operating stroke of the lever 24.

With such a hydraulic circuit, the function of the pressure compensating valve 18 makes it possible to distribute the flow rate in proportion to the opening area of the operating valve 15, regardless of the magnitude of the load on each hydraulic actuator 16.
The pressure oil discharged from one hydraulic pump 10 can be supplied to each hydraulic actuator 16 in proportion to the amount of operation of the operation valve 15.

In the above-mentioned hydraulic circuit, the lever 24 is operated to supply pilot pressure oil from the pilot control valve 23 to the operating valve 15 to open the operating valve 15 (that is, open the meter-in).
As the pressure is increased, the discharge pressure oil from the hydraulic pump 10 passes through the pressure compensating valve 18 and is sent to the hydraulic actuator 16. At this time, if the hydraulic actuator 16 is an actuator with large inertia, such as a swing motor or a boom cylinder, the drive starts. Since the pressure increases and the pump pressure is low at the initial stage of opening of the operation valve 15, the hydraulic actuator 16 cannot be driven at the same time as the operation valve 15 opens.

For this reason, since there is no difference between the load pressure and the pump pressure, the swash plate 11 is tilted in the direction of larger capacity by the small diameter piston 13, the pump pressure rises to the relief set pressure of the relief valve, and the high pump pressure The hydraulic actuator 16 suddenly starts driving with an acceleration that almost jumps out.

At this time, if the lever 24 is operated slowly and the opening area of the operating valve 15 increases slowly, the speed of the actuator 16 will exceed the target value corresponding to the opening area of the operating valve 15, and the hydraulic actuator The load pressure decreases because the pressure oil supply to 16 cannot be kept up.

As a result, the speed of the hydraulic actuator 16 decreases, and the driving pressure is increased again to accelerate the hydraulic actuator again, causing the hydraulic actuator to accelerate while hunting according to the lever operation, making smooth acceleration impossible.

Therefore, the applicant previously proposed the hydraulic circuit shown in FIGS. 2 and 3.

That is, as shown in FIG. 2, a throttle 31 is provided in the load sensing inlet circuit 30, a bypass circuit 32 is connected to the downstream side of the throttle 31, and this bypass circuit 32 is connected to a tank or a low pressure circuit by a bypass valve 33. Cut off.

The bypass valve 33 is held in a communication position I by a spring 34 and communicated through a throttle 35, and becomes a pilot pressure-operated valve that is in a shutoff position ■ by pilot pressure oil in a pressure receiving part 36, and the pressure receiving part 36 is connected to the pilot control valve. It is connected to the output side of 23.

In such a hydraulic circuit, when the lever 24 is in the neutral position and the output pressure of the pilot control valve 23 is Okg/cj, the operation valve 15 is in the closed center, so the opening area is zero (blocked state), and the bypass valve 33 is closed to the spring 34. At the communication position I, the load sensing inlet circuit 30 is communicated with the tank or the low pressure circuit via the bypass path 32.

From the above state, operate the lever 24 to close the pilot control valve 2.
3 outputs pilot pressure to open the operation valve 15,
When pump discharge pressure oil is supplied to the hydraulic actuator 16 through the pressure compensation valve 18, if the hydraulic actuator has a large inertia as described above, the hydraulic actuator cannot start driving and the load pressure increases rapidly.

However, since the load sensing inlet circuit 30 is connected to the tank or low pressure circuit through the bypass valve 33 through the bypass path 32, a portion of the load pressure mentioned above flows into the tank or the low pressure circuit and the detected load pressure is is lower than the actual load pressure, and the pump pressure - load pressure) is the actual (pump pressure -
load pressure), the switching valve 14 switches in the capacity decreasing direction, and the swash plate 11 of the hydraulic pump 10 slowly tilts in the capacity increasing direction, so that the capacity increases slowly, so that the load pressure does not increase. It becomes gentle.

Therefore, the acceleration of the hydraulic actuator 16 becomes gradual, and the speed of the actuator 16 becomes a speed commensurate with the opening area of the operating valve 15, and does not overshoot the target value, so hunting does not occur as in the conventional case.

In addition, when the lever 24 is operated to a certain set value, for example a full stroke, from the above-mentioned state, when the output pressure of the pilot control valve 23 reaches the set pressure, the pilot valve 33 becomes the cutoff position ■, and the load pressure suddenly increases as in the conventional case. However, since the opening area of the operating valve 15 is large and the target speed is large, hunting does not occur and the response is improved.

In the hydraulic circuit shown in FIG. 3, the load sensing inlet circuit 30 is throttled 37 and the circuit 39 includes a check valve 38.
and is connected to the outlet side of the pressure compensation valve 18.

[Problem to be solved by the invention]

Such a hydraulic circuit requires the bypass valve 33, which not only complicates the structure but also makes the piping troublesome.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide an operating valve for use in a hydraulic circuit that can solve the above-mentioned problems.

[Means and effects for solving the problem] An oil passage for supplying output pressure to the load sensing inlet circuit and an oil passage for communicating and blocking the oil passage to the tank port are drilled in the spool of the operation valve, and the operation valve is The valve itself has the function of a bypass valve.

〔Example〕

As shown in FIG. 1, the operation valve 15 is constructed by fitting the spool 42 into the spool hole 41 of the valve body 40, and sliding the spool 42 using the pilot pressure in the pressure receiving chamber 43 to connect the small diameter portion 44 of the spool 42 to the inlet port. 45 to the outlet port 46, and actuator port 47 and tank port 48.
It is designed to connect and block the communication.

A shuttle valve 21 is provided in the valve body 40, and an inlet of the shuttle valve 21, that is, a load sensing inlet circuit 30, opens into a port 49 of the spool hole 41, and an axial hole 50 bored in the axial direction of the spool 42. One end in the longitudinal direction opens to the outer peripheral surface with a passage 51, and the middle part in the longitudinal direction has a pore 52.
The small diameter portion 44 of the spool 42 is opened at the spool 42, and the other end in the longitudinal direction is opened at the outer circumferential surface with a pore 53.

Therefore, when the output pressure of the pilot control valve 23 is zero, the spool 42 is in the neutral position, the inlet port 45 and the outlet port 46 are blocked, and the meter-in opening is zero, the passage 51 communicates with the port 49 and the pore 53 is closed. Tank port 4
8, the load sensing inlet circuit 30 communicates with the tank port 48 through the small hole 53, and is in the same state as when the bypass valve 33 is in the communication position (2) shown in FIG.

When the lever 24 is operated to supply the output pressure of the pilot lllJan 23 to the pressure receiving chamber 43 and the spool 42 is slid in the direction of the arrow to communicate the inlet port 45 and the outlet port 46, the small hole 53 opens to the tank port 48. As the area gradually decreases and the spool 42 slides a predetermined stroke, the pore 53 is closed and the load sensing inlet circuit 30 and the tank port 48 are cut off, so the bypass valve 33 in FIG.
The state is the same as when the switch is at the cutoff position ■.

The shaft hole 50 and passage 51 drilled in the spool 42 in this way
Since the pores 52 and 53 perform the same function as a bypass valve, a bypass valve is not necessary.

〔Effect of the invention〕

When the opening area of the inlet port 45 and the outlet port 4B of the operation valve 15 is small, a part of the load pressure flows into the tank through the oil passage bored in the spool 42, and the detected load pressure becomes lower than the actual load pressure. , a differential pressure occurs between the pump pressure and the load pressure, and the response of the pump capacity change to the change in the opening area of the operating valve 15 becomes gradual, and the drive pressure rises slowly when driving a hydraulic actuator with large inertia, resulting in hunting. can be prevented.

Furthermore, since the operation valve 15 itself has the function of a bypass valve, there is no need to provide a bypass valve outside the operation valve 15, and the structure is simple and piping work is easy.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an operating valve showing an embodiment of the present invention, and FIGS. 2, 3, and 4 are hydraulic circuit diagrams previously proposed. 10 is a hydraulic pump, 10a is a discharge path, 15 is an operating valve, 1
6 is a hydraulic actuator, 18 is a pressure compensation valve, 30 is a load sensing inlet circuit, 40 is a valve body, 41 is a spool hole, 42 is a spool, 45 is an inlet port, 46 is an outlet port, and 48 is a tank port. Figure Figure

Claims (1)

[Claims] A plurality of operation valves 15 are provided in the discharge path 10a of the hydraulic pump 10, and a pressure compensation valve 18 is provided in the connection circuit between each operation valve 15 and each hydraulic actuator 16, and each pressure compensation valve 1
8 is set at the highest pressure among the load pressures of each hydraulic actuator 16, and the inlet port 45 is connected to the spool hole 41 of the valve body 40 in an operation valve used in a hydraulic circuit that controls the pump displacement by the differential pressure between the pump pressure and the load pressure. A spool 42 is inserted into the spool 42 for communicating and blocking the outlet port 46, and an oil passage for supplying output pressure to the load sensor inlet circuit 30 provided in the valve body 40 and the oil passage for communicating and blocking the tank port 48 are inserted into the spool 42. An operating valve for use in a hydraulic circuit, characterized in that the load sensing inlet circuit 30 can be communicated with and cut off from the tank side by the sliding of the spool 42 by perforating the oil passage.